WEBVTT - From the Vault: Thirst, Part 3 0:00:05.800 --> 0:00:07.920 Hey, you welcome to Stuff to Blow your Mind. My 0:00:08.000 --> 0:00:11.280 name is Robert Lamb and I'm Joe McCormick, and it's Saturday. 0:00:11.320 --> 0:00:13.760 Time to go into the vault for an older episode 0:00:13.760 --> 0:00:17.240 of the show. This one originally aired on February eighth, 0:00:17.600 --> 0:00:21.640 twenty twenty two. It's part three of our series about thirst. 0:00:22.079 --> 0:00:27.520 Let's jump right in. Welcome to Stuff to Blow Your Mind, 0:00:27.680 --> 0:00:37.880 a production of iHeartRadio. Hey, welcome to Stuff to Blow 0:00:37.920 --> 0:00:41.159 your Mind. My name is Robert Lamb and I'm Joe McCormick, 0:00:41.200 --> 0:00:43.960 and we're back with part three of our series on 0:00:44.320 --> 0:00:47.720 the question of thirst. Now, if you remember, in the 0:00:47.760 --> 0:00:53.120 last episode, Rob we talked about the biology of thirst, 0:00:53.280 --> 0:00:58.680 anticipation of anticipation of the quenching of thirst. Because there's 0:00:58.720 --> 0:01:01.600 this interesting thing where after you drink a glass of 0:01:01.640 --> 0:01:05.160 water when you've been dehydrated, it takes some number of minutes, 0:01:05.200 --> 0:01:08.080 maybe on the order of tens of minutes before that 0:01:08.120 --> 0:01:11.640 water actually gets absorbed through the digestive system and ends 0:01:11.720 --> 0:01:14.600 up in the blood and makes a difference systemically throughout 0:01:14.640 --> 0:01:18.680 the body. And yet you still feel that that thirst 0:01:18.760 --> 0:01:21.920 quinchiness after you have just the first glass of water. 0:01:21.959 --> 0:01:25.680 You're not continuously chugging for ten to twenty minutes at 0:01:25.760 --> 0:01:29.440 least hopefully not. But to start off today, I wanted 0:01:29.480 --> 0:01:32.720 to come back to the question of how it is 0:01:32.840 --> 0:01:39.480 that the body detects, the anticipates the coming changes in 0:01:39.520 --> 0:01:42.600 your blood and your blood osmolality, which again is the 0:01:43.000 --> 0:01:48.160 concentration of dissolved substances like mineral salts in your body's 0:01:48.200 --> 0:01:53.680 water content, and how it anticipates those changes to provide 0:01:53.720 --> 0:01:57.000 you that delicious feeling of having your thirst quenched by 0:01:57.000 --> 0:01:59.280 a glass of water. Now, in the previous episodes, we 0:01:59.320 --> 0:02:02.720 already talked about a few ways that the mouth in 0:02:02.800 --> 0:02:07.280 the throat might detect the introduction of water into the 0:02:07.320 --> 0:02:11.160 body and sort of sin signals to the brain saying hey, okay, 0:02:11.200 --> 0:02:13.640 you can put the thirst on hold for now, there 0:02:13.680 --> 0:02:17.360 are soon coming changes to the body's hydration levels. And 0:02:17.720 --> 0:02:20.119 one of the ideas we talked about was the possibility 0:02:20.160 --> 0:02:23.600 that temperature plays a role, because maybe there's some evidence 0:02:23.680 --> 0:02:26.600 that the power of water to cool the mouth and 0:02:26.680 --> 0:02:31.120 throat sends quinching signals to the brain. And also there 0:02:31.240 --> 0:02:36.160 was some evidence that rodents were using sour taste receptors 0:02:36.200 --> 0:02:38.560 in the mouth to detect the presence of water. But 0:02:38.919 --> 0:02:41.359 Rob maybeing set me straight on this one. I don't 0:02:41.480 --> 0:02:45.760 think it was clear that triggering the sour taste receptors 0:02:46.160 --> 0:02:49.160 actually led to the quinching of thirst. Rather, it seemed 0:02:49.200 --> 0:02:53.320 to encourage more drinking behavior when the mouse was thirsty. 0:02:53.480 --> 0:02:56.399 Is that right? Yes, that's my understanding of these findings. 0:02:56.639 --> 0:02:59.800 But I was actually reading about a few more studies 0:02:59.800 --> 0:03:03.400 on exactly this question of how thirst quinching happens. What 0:03:03.560 --> 0:03:06.520 is the mechanism that leads to these changes in the 0:03:06.520 --> 0:03:10.359 brain that tell you, aha, thou art now quinched. So 0:03:10.680 --> 0:03:12.440 the first thing I wanted to talk about was a 0:03:12.440 --> 0:03:14.400 study that I was reading about a New York Times 0:03:14.480 --> 0:03:18.919 article from twenty eighteen by Verny Greenwood called you get 0:03:18.960 --> 0:03:21.840 thirsty and drink? How does your brain signal you've had enough? 0:03:22.120 --> 0:03:25.119 And this is referring to a paper that I think 0:03:25.520 --> 0:03:29.040 came up in passing in the previous episode, but it 0:03:29.080 --> 0:03:32.359 was by Vinnie Augustine at all in Nature in twenty 0:03:32.400 --> 0:03:37.400 eighteen called Hierarchical neural architecture underlying thirst regulation. And this 0:03:37.440 --> 0:03:39.880 research has been looking at exactly this question we just 0:03:39.920 --> 0:03:43.000 brought up, and they confirmed that, of course there is 0:03:43.040 --> 0:03:46.040 a complex of neurons in the brain that appear to 0:03:46.320 --> 0:03:50.720 cease activity after a thirsty mouse drinks water. So there 0:03:50.720 --> 0:03:54.560 are some neurons that are apparently signaling that generating that 0:03:54.720 --> 0:03:58.280 thirst motivation state. But then when a rodent takes some 0:03:58.360 --> 0:04:01.520 water in through the mouth, those rons shut up, they 0:04:01.600 --> 0:04:04.560 go quiet. So this would be the neural mechanism to 0:04:04.640 --> 0:04:07.560 register quenching. But the question is what is the direct 0:04:07.680 --> 0:04:13.040 mechanism that leads to the changes in those neurons. Now, 0:04:13.040 --> 0:04:16.320 this New York Times article summarizes the findings as explained 0:04:16.320 --> 0:04:21.279 by the first author on that paper, Vanite Augustine quote, Intriguingly, 0:04:21.400 --> 0:04:24.640 what these cells are responding to is not the presence 0:04:24.680 --> 0:04:29.320 of water itself, mister Augustine said. The researchers discovered that 0:04:29.480 --> 0:04:32.880 letting a mouse take big gulps of water would spur 0:04:32.960 --> 0:04:37.240 the neurons into action, but giving it water in gel form, 0:04:37.640 --> 0:04:40.320 which had to be chewed before it could be swallowed, 0:04:40.480 --> 0:04:44.479 did not. Neither did providing water in tiny two second 0:04:44.520 --> 0:04:48.400 long SIPs, even when the animals consumed the same total 0:04:48.480 --> 0:04:52.000 amount of water. In fact, giving the mice oil to 0:04:52.120 --> 0:04:55.200 drink had just the same effect on the neurons as 0:04:55.240 --> 0:04:58.719 gulping water. So that last part is a little gross, 0:04:58.839 --> 0:05:01.479 but based on this fine name, uh, it would kind 0:05:01.480 --> 0:05:05.159 of imply that a major mechanism leading these thirst neurons 0:05:05.200 --> 0:05:08.560 to to say, okay, thirst has been quenched would have 0:05:08.600 --> 0:05:11.599 something to do with like muscular movements in the throat, 0:05:11.640 --> 0:05:14.159 the kind of gulping that you do when you're guzzling 0:05:14.160 --> 0:05:17.080 down a bunch of water really fast. But technically maybe 0:05:17.120 --> 0:05:19.239 it doesn't even have to be water, it's just any 0:05:19.240 --> 0:05:22.640 fluid that you're gulping. I mean, as humans, we don't 0:05:22.680 --> 0:05:24.880 I guess, drink a lot of just straight oil, but 0:05:24.960 --> 0:05:26.839 we do drink a lot of things that are that 0:05:26.960 --> 0:05:31.599 are to varying degrees removed from from from you know, 0:05:31.839 --> 0:05:36.800 from from just a neutral water. So this would make sense, right, 0:05:36.920 --> 0:05:39.840 But if you if you hydrate yourself in some other ways, 0:05:39.839 --> 0:05:42.560 so like the examples that you say, consuming water in 0:05:42.680 --> 0:05:45.719 gel form where you can't like gulp it down really 0:05:46.400 --> 0:05:49.640 that still hydrates you, but that apparently does not lead 0:05:49.680 --> 0:05:53.720 to this immediate quinching signal in the brain. Similarly, with 0:05:53.800 --> 0:05:57.719 drinking water in very small isolated SIPs, I guess in 0:05:57.760 --> 0:06:01.400 those cases you would eventually hydrate your self and your 0:06:01.480 --> 0:06:04.560 thirst will eventually go away, but it will be more 0:06:04.560 --> 0:06:08.000 likely that your body has to just become systemically hydrated 0:06:08.480 --> 0:06:11.760 before the thirst goes away. It's not that sudden quinching 0:06:11.839 --> 0:06:15.880 reward feeling. Now, there was an interesting detail offered here 0:06:16.000 --> 0:06:19.400 about reasons that the body might need to have this 0:06:19.440 --> 0:06:22.599 reaction where we turn off thirst very quickly after getting 0:06:22.600 --> 0:06:26.200 a drink, like why not just wait for your blood 0:06:26.200 --> 0:06:30.760 osmolality to reach the ideal level. Well, in previous episodes, 0:06:30.760 --> 0:06:33.080 we talked about one reason for this, which is that 0:06:33.160 --> 0:06:35.320 you know, if you actually did have to wait for 0:06:35.440 --> 0:06:38.320 your body's water content to get all leveled out right 0:06:38.360 --> 0:06:41.320 before your thirst went away, you might you might like 0:06:41.880 --> 0:06:45.240 kill yourself drinking gallons and gallons of water because you 0:06:45.240 --> 0:06:47.240 know over the course of the tens of minutes that 0:06:47.320 --> 0:06:50.800 it takes for this change to take hold. But there's 0:06:50.839 --> 0:06:53.120 another reason, one of the authors of this paper brings up. 0:06:53.120 --> 0:06:56.839 That's in this Greenwood article in the Times quote. Aside 0:06:56.839 --> 0:06:59.800 from the specter of water intoxication, there are good reasons 0:06:59.839 --> 0:07:03.520 to drink only the minimum amount necessary when an animal 0:07:03.600 --> 0:07:06.839 lowers its head to drink, doctor Oka speculated, and that's 0:07:06.880 --> 0:07:11.480 doctor Yukioka. It's in quite a vulnerable position. Quote, if 0:07:11.480 --> 0:07:14.240 you double the time of ingestion, that should double the 0:07:14.360 --> 0:07:17.880 risk of being prey, he said, And I thought that 0:07:17.960 --> 0:07:20.160 was interesting too. I mean, I think it is true 0:07:20.200 --> 0:07:22.440 that in the natural environment, as we brought up in 0:07:22.440 --> 0:07:26.040 the previous episode, going for water is often putting yourself 0:07:26.120 --> 0:07:30.360 in a vulnerable position, you know, maybe exposing yourself from 0:07:30.440 --> 0:07:33.800 hiding or shelter and sort of turning your attention away 0:07:33.840 --> 0:07:38.800 from scanning your surroundings. Yeah. I mean in many cases too, 0:07:38.920 --> 0:07:41.960 they the access point of the water might not provide 0:07:42.120 --> 0:07:44.680 much in the way of cover for smaller animals, and 0:07:44.720 --> 0:07:49.120 then for larger animals there may be you know, bodily 0:07:49.160 --> 0:07:52.720 positions they have to get into to drink that put 0:07:52.760 --> 0:07:56.480 them in a greater state of vulnerability. Like I'm thinking 0:07:56.520 --> 0:07:59.800 of a draft for instance. Though draft, of course is 0:07:59.800 --> 0:08:05.200 already formidable animal U but but still there's a certain 0:08:05.240 --> 0:08:08.880 awkwardness present when it actually has to drink water. Sorry, 0:08:09.000 --> 0:08:14.200 I just started thinking about game or fuel. Um, yeah, 0:08:14.240 --> 0:08:16.400 this is this, says. I have no research to back 0:08:16.440 --> 0:08:20.120 this up. They're just observational material for me. But I 0:08:20.120 --> 0:08:23.640 think everyone knows that I enjoy watching the squirrels, and 0:08:24.560 --> 0:08:29.840 we have a bird bath outside near our feeders, and 0:08:29.920 --> 0:08:32.920 the bird bath is positioned right up against the fence, 0:08:33.400 --> 0:08:36.200 and the squirrels drink from that all the time. But 0:08:36.320 --> 0:08:38.560 I wonder how much I wonder how much of that 0:08:38.720 --> 0:08:41.400 is that they're able to drink from the bird bath 0:08:41.920 --> 0:08:47.040 while essentially remaining in a vertical position attached to the 0:08:47.240 --> 0:08:49.880 to the fence, like they don't have to, you know, 0:08:49.920 --> 0:08:52.320 go across a clearing. They have, I guess, pretty good 0:08:52.360 --> 0:08:55.640 cover for a squirrel. Those squirrels are bold in other 0:08:55.679 --> 0:08:58.240 ways that, you know, make you think that they're they're 0:08:58.360 --> 0:09:01.120 less concerned, or they're or they're in control of the 0:09:01.160 --> 0:09:04.600 situation as far as potential predators go. So if you 0:09:04.640 --> 0:09:07.800 happen to have sitter squirrels and rover squirrels, your bird 0:09:07.800 --> 0:09:09.880 bath is positioned in such a way that even the 0:09:09.920 --> 0:09:13.000 sitter squirrels could could get to it. I guess so. 0:09:13.240 --> 0:09:15.080 But then, yeah, I don't know. I'd be interested to 0:09:15.080 --> 0:09:17.240 hear what anyone else out there has observed with their 0:09:17.240 --> 0:09:22.679 squirrels and drinking water from bird baths and other water sources. 0:09:23.520 --> 0:09:25.360 They seem to like one thing versus the other. I 0:09:25.360 --> 0:09:27.600 don't know. They certainly drink more water than my cat. 0:09:28.000 --> 0:09:31.440 I'll give them that well. Anyway, there was another article 0:09:31.800 --> 0:09:34.200 from the very next year, also in the New York Times, 0:09:34.240 --> 0:09:37.600 also by Greenwood, covering follow up research from some of 0:09:37.600 --> 0:09:40.760 the same scientists. So this was published May thirty first, 0:09:40.800 --> 0:09:45.079 twenty nineteen, just called the Neurobiology of Thirst, and this 0:09:45.120 --> 0:09:48.559 is summarizing a study published in twenty nineteen in the 0:09:48.640 --> 0:09:52.640 journal Neuron where the authors oh again the first author 0:09:52.679 --> 0:09:56.160 on this one was Vanite Augustine and it was called 0:09:56.240 --> 0:10:02.200 Temporally and spatially distinct thirst satiation Sig and the authors 0:10:02.240 --> 0:10:05.439 here found that the pleasure we get from drinking when 0:10:05.480 --> 0:10:09.680 thirsty is once again not directly related to hydration. It 0:10:09.800 --> 0:10:13.400 is a reward pathway separated by both time and space 0:10:13.559 --> 0:10:19.160 from the body's hydration and osmolality monitoring mechanisms. And one 0:10:19.200 --> 0:10:21.839 of the major findings in this paper is that though 0:10:22.080 --> 0:10:27.160 drinking water is associated with a dopamine release, this is 0:10:27.200 --> 0:10:31.240 a typical signal that the brain is expecting a reward. Right. 0:10:31.280 --> 0:10:33.960 You know, things that you want, you want to get 0:10:34.040 --> 0:10:36.920 and feel good when you get them. That's often that 0:10:36.960 --> 0:10:41.120 involves a dopamine release. But the feeling of reward in 0:10:41.120 --> 0:10:44.960 the brain here is apparently not tied to becoming hydrated 0:10:45.000 --> 0:10:49.559 after being dehydrated, but specifically to the act of drinking 0:10:49.600 --> 0:10:53.040 water through the mouth. So if you're dehydrated and then 0:10:53.080 --> 0:10:56.640 you suddenly receive water through an iv or even via 0:10:56.679 --> 0:11:00.680 a direct injection into the stomach, your thirst will eventually 0:11:00.760 --> 0:11:03.800 go away after your body adjusts to the new fluid levels, 0:11:04.160 --> 0:11:07.920 but you won't get that feeling of reward satisfaction or 0:11:07.960 --> 0:11:12.679 the corresponding dopamine release. Those come specifically from the activity 0:11:12.679 --> 0:11:15.880 of drinking, the gulping of water through the mouth. And 0:11:16.080 --> 0:11:17.920 picking up on this, I was actually looking at one 0:11:17.960 --> 0:11:20.640 more paper that had an interesting finding. I wouldn't have 0:11:20.679 --> 0:11:23.560 mentioned this. Other one was a little earlier. This was 0:11:23.640 --> 0:11:28.120 from twenty sixteen published in Nature called thirst neurons anticipate 0:11:28.200 --> 0:11:31.640 the homeostatic consequences of eating and drinking, And this is 0:11:31.679 --> 0:11:36.280 by Zimmerman at All And this study found, among other things, 0:11:36.320 --> 0:11:42.000 a dual track monitoring system for thirst management. So along 0:11:42.040 --> 0:11:44.680 the lines we've already been talking about. It found that 0:11:44.720 --> 0:11:47.320 if you take mice and you give them some salt 0:11:47.320 --> 0:11:52.240 and make them thirsty, drinking water rapidly inhibits neurons in 0:11:52.679 --> 0:11:56.240 a region of the brain called the subfornical organ or SFO, 0:11:56.360 --> 0:11:59.720 and that leads to thirst quenching. And of course this 0:11:59.800 --> 0:12:03.200 is before there's any notable change in blood osmolality. But 0:12:03.400 --> 0:12:06.640 it also found that if you take these thirsty mice 0:12:06.800 --> 0:12:11.320 and you give them very salty water and the opportunity 0:12:11.360 --> 0:12:14.280 to drink it, they will drink it, and initially they 0:12:14.320 --> 0:12:18.000 will gulp it down and it will inhibit the SFO 0:12:18.080 --> 0:12:22.120 neurons and apparently quench thirst just like the freshwater. But 0:12:22.320 --> 0:12:26.080 the quenching doesn't last for very long, and they write quote, 0:12:26.200 --> 0:12:30.400 this initial decline was reversed after approximately one minute. This 0:12:30.480 --> 0:12:33.920 indicates that the rapid anticipatory response to drinking has at 0:12:33.960 --> 0:12:38.360 least two components, an immediate signal that tracks fluid ingestion 0:12:38.720 --> 0:12:43.040 and a delayed signal that reports on fluid tonicity, possibly 0:12:43.080 --> 0:12:48.160 generated by an esophageal or gastric osmo sensor. So if 0:12:48.160 --> 0:12:50.360 you put all of this together, it seems like you've 0:12:50.360 --> 0:12:54.720 got at least three different time dependent levels of sort 0:12:54.760 --> 0:12:58.200 of the body's quinch watch. So you put them all together, 0:12:58.280 --> 0:13:01.680 and you've got one system that's like, are you gulping fluid? 0:13:01.800 --> 0:13:04.600 If you are, oh, that's very good, very good thou 0:13:04.679 --> 0:13:07.840 art quinched, But then there's a second system on a 0:13:07.880 --> 0:13:10.880 slight delay from that one, roughly one minute of delay 0:13:10.920 --> 0:13:15.240 in mice. It's like, wait a second, what exactly was 0:13:15.360 --> 0:13:18.320 that you were just gulping? Was that oil or was 0:13:18.360 --> 0:13:21.480 that super salty water? You know, what are you trying 0:13:21.520 --> 0:13:23.480 to pull? And if it well, if it was not 0:13:23.880 --> 0:13:27.760 good fresh water, then it will cancel, cancel the quinch 0:13:27.960 --> 0:13:31.439 and return the thirst. And then finally I guess there's 0:13:31.480 --> 0:13:34.800 just the direct blood volume in osmolality monitoring, which is 0:13:34.800 --> 0:13:37.800 on a much greater delay than the other two. So, 0:13:37.880 --> 0:13:41.120 first of all, reminder, if anyone else, if anyone's interested 0:13:41.120 --> 0:13:42.880 in the whole drinking saltwater thing, we did a whole 0:13:42.920 --> 0:13:46.839 episode on drinking saltwater a while back. You should be 0:13:46.840 --> 0:13:49.160 able to find that in the archives. Not a good 0:13:49.160 --> 0:13:51.720 idea was it was one of the main findings there. 0:13:52.880 --> 0:13:55.120 But the other thing, I think, and we've kind of 0:13:55.200 --> 0:13:56.920 we've kind of touched on this a little bit already, 0:13:56.960 --> 0:14:00.440 but you know, it would be in a steak to 0:14:00.480 --> 0:14:02.680 think of like, Okay, it's just you know, what's drinking water, 0:14:02.760 --> 0:14:06.560 water in water out, you know, even if you you 0:14:06.679 --> 0:14:08.840 then acknowledge, okay, well, you know, the levels have to 0:14:08.880 --> 0:14:10.880 be just right. But it's it's more than that. It's 0:14:10.880 --> 0:14:14.720 not like organisms just one day we're like, hey, there's 0:14:14.760 --> 0:14:16.800 water we can drink that we should use this to 0:14:16.800 --> 0:14:19.640 our advantage. Now, like we are of water. So it's 0:14:19.680 --> 0:14:25.560 like water in am water evolved out of things in water, etc. 0:14:26.000 --> 0:14:28.080 So it's it makes sense that there would be a 0:14:28.120 --> 0:14:32.200 more complex relationship with multiple triggers that you know that 0:14:33.000 --> 0:14:36.240 we're still trying to understand. Yeah, I mean, as we 0:14:36.280 --> 0:14:38.800 said at the very beginning, you you are the direct 0:14:38.920 --> 0:14:41.960 descendant of creatures that long ago lived in the ocean 0:14:42.040 --> 0:14:44.720 and all of your ancestors, just like you brought the 0:14:44.720 --> 0:14:48.200 ocean with you onto land. The ocean is now inside 0:14:48.200 --> 0:14:51.200 your skin. Yes. Oh, and before I wrap up, this 0:14:51.280 --> 0:14:56.360 last study I mentioned also documents interesting evidence for the 0:14:56.360 --> 0:14:59.680 the oral cooling mechanism of thirst quenching that I brought 0:14:59.720 --> 0:15:03.880 up in previous episode. So the authors here say that quote. 0:15:03.920 --> 0:15:07.280 We found that a playing cold but not room temperature 0:15:07.480 --> 0:15:11.400 metal to the oral cavity of a wake thirsty mice 0:15:11.960 --> 0:15:17.200 was sufficient to rapidly inhibit SFO neurons. Thus, temperature dependent 0:15:17.280 --> 0:15:21.920 modulation of SFO neurons may explain the enigmatic connection between 0:15:22.040 --> 0:15:26.360 oral cooling and thirst, including why thirsty rodents will avidly 0:15:26.480 --> 0:15:30.400 lick cold metal, and humans report that sucking on ice 0:15:30.480 --> 0:15:35.200 chips rapidly relieves thirst. That's interesting. I hadn't really thought 0:15:35.200 --> 0:15:38.880 about that with sucking on ice chips though, though obviously, 0:15:39.000 --> 0:15:40.760 I mean that's I think that's something we all do 0:15:40.840 --> 0:15:45.000 if we have access to iced drinks. Of course, the 0:15:45.000 --> 0:15:47.440 thing with ice, of course, is that ice melts in 0:15:47.440 --> 0:15:50.840 your mouth as well and actually serves to hydrate you, right, 0:15:50.880 --> 0:15:53.960 but that the cooling effect of having the ice in 0:15:53.960 --> 0:15:59.080 the mouth may provide a level of thirst quenching sensation 0:15:59.160 --> 0:16:01.960 that goes beyond the actual amount of water you're taking 0:16:02.000 --> 0:16:06.000 in from that ice. This gives me a great idea, so, 0:16:06.880 --> 0:16:09.960 showrunners and so forth, of the Witcher, if you're listening, 0:16:10.240 --> 0:16:12.640 I would love to see a scene where Henry Cavill's 0:16:13.320 --> 0:16:17.480 Witcher character share some wisdom and he's like, sometimes when 0:16:17.800 --> 0:16:19.920 when I'm thirsty, I just have a good lick of 0:16:19.960 --> 0:16:23.000 my sword takes care of you know. That'd be great, 0:16:23.040 --> 0:16:24.520 And you haven't seen there was just kind of licking 0:16:24.640 --> 0:16:27.040 is the blade of his sword. I'd never heard this 0:16:27.160 --> 0:16:31.440 before that apparently thirsty, thirsty rodents will lick cold metal. 0:16:31.560 --> 0:16:34.720 But yeah, I had not seen it. Yeah, but it's 0:16:34.720 --> 0:16:36.640 good enough for mice, it's good enough for the witcher. 0:16:36.920 --> 0:16:39.600 I think all Garrold's just gonna that's that's how you 0:16:39.640 --> 0:16:42.000 cut your tongue, buddy, That's how you cut your tongue. 0:16:42.360 --> 0:16:44.920 Oh you know. It reminds me of brom Stoker's Dracula. 0:16:44.960 --> 0:16:49.680 We have that wonderful scene where Gary Oldman's elderly Dracula 0:16:50.120 --> 0:16:53.720 licks the blood from the straight razor. See, he was 0:16:53.760 --> 0:16:57.200 thirsty and he quenched the thirst. But also hopefully the 0:16:57.720 --> 0:17:00.360 blade was cold enough that that also had an fact. 0:17:00.360 --> 0:17:02.560 I well, I guess after all these studies we looked 0:17:02.600 --> 0:17:07.120 at on the quenching mechanism, I'm wondering, so the two 0:17:07.160 --> 0:17:10.960 main different ones have emerged. One is the oral cooling 0:17:11.000 --> 0:17:13.960 mechanism and the other is the gulping mechanism. You know, 0:17:13.960 --> 0:17:16.560 the muscular movements in the throat is you're swallowing large 0:17:16.560 --> 0:17:19.520 amounts of water. And I guess I'm not sure if 0:17:19.600 --> 0:17:23.000 these two different explanations are competing or if they're complementary. 0:17:23.040 --> 0:17:26.400 Maybe they both play a role in regulating these thirst neurons. 0:17:26.400 --> 0:17:35.639 In the SFO. I'm not sure. Now, given all the 0:17:35.680 --> 0:17:39.520 things we've discussed about the complexity of thirst, sensations, and 0:17:39.760 --> 0:17:44.320 water acquisition by various organisms, I thought it might be 0:17:44.840 --> 0:17:47.879 interesting to look at a couple of examples that, in 0:17:47.960 --> 0:17:53.800 different ways seem to hijack mechanisms of related to thirst 0:17:53.880 --> 0:17:57.520 and our relationship with water, not only ours, but also 0:17:57.600 --> 0:18:01.639 some other organisms for the benefit of a life form. 0:18:01.840 --> 0:18:05.640 Not the life form that is that is potentially thirsty, 0:18:05.840 --> 0:18:11.080 but a life form that is that is hijacking that organism, 0:18:11.840 --> 0:18:16.480 such as a parasite or a virus. Oh. Interesting. So 0:18:17.080 --> 0:18:19.600 the first one I want to mention here is is 0:18:19.600 --> 0:18:23.200 one that definitely affects humans, and that is rabies. Now, 0:18:23.240 --> 0:18:26.240 I imagine I think everyone has heard of rabies. If not, 0:18:26.320 --> 0:18:28.960 buckle in because I'm gonna share a little bit. Though. 0:18:28.960 --> 0:18:31.240 This is obviously a topic that you know, we could 0:18:31.240 --> 0:18:33.639 really bust out if we wanted to and give a 0:18:33.680 --> 0:18:37.040 full episode treatment. But even if you're just vaguely familiar 0:18:37.040 --> 0:18:39.760 with rabies, uh, you know, you might not grasp the 0:18:39.800 --> 0:18:43.880 full danger and horror of this particular zoonotic viral disease. 0:18:44.280 --> 0:18:46.240 I think a while back, I've read at least somebody 0:18:46.320 --> 0:18:50.159 making the case that rabies is a contender for like 0:18:50.240 --> 0:18:54.920 the worst disease known. Yeah, it is pretty horrifying and 0:18:55.080 --> 0:18:58.760 for a lot of people in um in the world, 0:18:58.800 --> 0:19:02.240 particularly and let's let's say United States, you're lucky enough 0:19:02.440 --> 0:19:07.399 to live largely removed from it. I think that the 0:19:07.520 --> 0:19:11.800 US is sometimes class of classified as being free of 0:19:11.920 --> 0:19:15.520 canine rabies. Now, there are still cases of canine rabies 0:19:15.560 --> 0:19:18.640 that pop up, and there are deaths that occur, but 0:19:18.880 --> 0:19:20.679 not at the same rate as other parts of the 0:19:20.680 --> 0:19:23.080 world where the problem has not been contained as well. 0:19:24.000 --> 0:19:27.520 So it's rabies is caused by the virus Lisa virus, 0:19:27.720 --> 0:19:31.280 which essentially means rage poison. It's named for the Greek 0:19:31.320 --> 0:19:36.480 goddess Lissa, the goddess of rage, fury and rabies, the 0:19:37.040 --> 0:19:42.600 daughter of Nicks, sprung from the blood of Lauranus, and 0:19:42.760 --> 0:19:44.800 she pops up in different tales, like for instance, at 0:19:44.800 --> 0:19:49.159 the urging of Hera, she inflicts madness on Heracles, and 0:19:49.200 --> 0:19:51.679 in some tellings she's also involved in the punishment of 0:19:51.680 --> 0:19:55.160 the hunter Acteon, who's torn apart by his own mad 0:19:55.320 --> 0:19:58.200 hunting dogs, and in memory Serves. There are some interesting 0:19:59.119 --> 0:20:03.359 treatments of the this latter tale in art. Yeah, I 0:20:03.400 --> 0:20:06.400 think he looked at a god or something to that effect. 0:20:07.200 --> 0:20:08.640 You know, you don't have to do much to get 0:20:08.640 --> 0:20:10.760 to torn apart by dogs when you're dealing with the 0:20:11.680 --> 0:20:14.399 Greek pantheon. Yeah. I don't remember all the details, but 0:20:14.440 --> 0:20:17.719 I think he makes Artemis angry for some reason, and 0:20:17.760 --> 0:20:22.360 then he's a hunter. But then he's transformed into the quarry, 0:20:22.440 --> 0:20:24.960 like he's transformed into a stag or something, and then 0:20:25.000 --> 0:20:28.000 his own hunting dogs hunt atch. Right, there's some transformation 0:20:28.080 --> 0:20:31.080 involved there as well. So humans have been exposed to 0:20:31.160 --> 0:20:34.520 rabies for a very long time. It's um. It's thought 0:20:34.520 --> 0:20:38.720 that it probably originated in old world bats and especially 0:20:38.760 --> 0:20:43.199 flourished during the heyday of of dog domestication. So it is, 0:20:43.520 --> 0:20:47.399 you know, it is. It is definitely tied to the 0:20:47.480 --> 0:20:51.879 canine world. According to the History of Rabies in the 0:20:51.880 --> 0:20:56.879 Western Hemisphere by Velasco Villa at All, published in Anti 0:20:57.000 --> 0:21:02.440 Viral Research, the earliest record of a disease affecting humans 0:21:02.480 --> 0:21:06.919 that's consistent with rabies and associated with dogs is found 0:21:07.040 --> 0:21:12.000 in the Eshnuna cuneiform law tablets in ancient Mesopotamia dating 0:21:12.000 --> 0:21:17.120 back to the eighteenth through nineteenth centuries BC. Wow, Yeah, 0:21:17.119 --> 0:21:20.000 and I believe memories served it. It concerns like laws 0:21:20.600 --> 0:21:24.199 concerning dogs biting people, like if you you have a 0:21:24.200 --> 0:21:26.840 dog and it bites somebody. And of course we have 0:21:26.880 --> 0:21:32.360 other references to either cases that seem like they could 0:21:32.400 --> 0:21:35.760 be rabies, or we feel pretty strongly are referring to rabies. 0:21:36.600 --> 0:21:39.560 Aristotle wrote seemed to have wrote of it in three 0:21:39.680 --> 0:21:44.640 thirty BC. Quote dogs suffer from the madness. This causes 0:21:44.680 --> 0:21:48.080 them to become very irritable, and all animals they bite 0:21:48.160 --> 0:21:52.560 become diseased. Democratus and Hippocrates also wrote of it as well, 0:21:52.640 --> 0:21:56.800 and there are comparisons to raging dogs in the Iliad 0:21:57.240 --> 0:21:59.800 that it seems like maybe you're less certain that this 0:21:59.880 --> 0:22:02.080 is referring, because of course a dog can rage. I 0:22:02.119 --> 0:22:05.119 guess it doesn't have to be rabid. But there are 0:22:05.160 --> 0:22:09.640 also mentions of the dog star Ryan exerting a malignant 0:22:09.680 --> 0:22:15.600 influence on human health, and rabies is just a terrible disease, 0:22:15.720 --> 0:22:19.080 especially when you really get into what it can do 0:22:19.359 --> 0:22:21.480 to an organism and what it can do to a 0:22:21.560 --> 0:22:27.520 human being. Today, it's vaccine preventable, and the vaccines keep improving, 0:22:27.960 --> 0:22:32.360 but once clinical symptoms appear, it is one fatal According 0:22:32.359 --> 0:22:36.520 to the World Health Organization, in ninety nine percent of cases, 0:22:36.720 --> 0:22:40.440 domestic dogs are responsible for spreading it to humans. Again, 0:22:40.480 --> 0:22:45.000 in the United States, it is effectively we're effectively canine 0:22:45.359 --> 0:22:49.000 rabies free, though you will still find cases that occur 0:22:49.160 --> 0:22:52.919 and deaths that occur, so it's it's still possible, but 0:22:53.080 --> 0:22:56.919 it is largely under control. In other parts of the 0:22:56.920 --> 0:22:59.439 world it's not the case. And so you know, this 0:22:59.520 --> 0:23:03.720 is all great reminder why it is important to get 0:23:03.760 --> 0:23:07.440 your dog a rabies vaccine and to also get yourself 0:23:08.160 --> 0:23:11.960 immunized if you come into contact with the disease, right, 0:23:12.520 --> 0:23:16.040 and that time is very important there, right, Yeah, so 0:23:16.080 --> 0:23:19.280 that the incubation period for rabies is typically two to 0:23:19.320 --> 0:23:22.560 three months, but may vary from one week to a year. 0:23:22.920 --> 0:23:25.040 And I think it depends on like the viral load 0:23:25.680 --> 0:23:28.320 and you know, being introduced into your body and some 0:23:28.400 --> 0:23:31.639 other factors. And then there are two forms of the 0:23:31.680 --> 0:23:34.439 disease that are possible in humans. So once you know 0:23:34.480 --> 0:23:39.360 this virus is in your system, one version is paralytic rabies. 0:23:39.400 --> 0:23:41.960 This only occurs in about twenty percent of cases, and 0:23:42.040 --> 0:23:47.200 it consists of gradual muscle paralyzation, coma, and death. It's 0:23:47.240 --> 0:23:51.240 often misdiagnosed, but again, like twenty percent of cases, this 0:23:51.320 --> 0:23:55.680 is what occurs. The other, however, is the the the 0:23:56.119 --> 0:24:00.720 incarnation of rabies that certainly brings to mind these ideas 0:24:00.720 --> 0:24:03.280 of strange curses from the gods, you know, the really 0:24:03.560 --> 0:24:09.680 horrible stuff, and that's furious rabies. Symptoms here include hyperactivity, 0:24:10.000 --> 0:24:16.680 excitable behavior, hydrophobia, the fear of water, and sometimes aerophobia 0:24:16.720 --> 0:24:19.679 as well, fear of drafts of fresh air or you know, 0:24:19.760 --> 0:24:23.640 blasts of air, that sort of thing. And death occurs 0:24:23.680 --> 0:24:27.200 in these cases within a few days due to cardiac arrest. Now, 0:24:27.200 --> 0:24:32.159