WEBVTT - Thirst, Part 3 0:00:00.160 --> 0:00:05.240 My Welcome to Stuff to Blow Your Mind, the production 0:00:05.240 --> 0:00:14.880 of My Heart Radio. Hey, welcome to Stuff to Blow 0:00:14.920 --> 0:00:18.200 Your Mind. My name is Robert lamp and I'm Joe McCormick, 0:00:18.239 --> 0:00:21.000 and we're back with part three of our series on 0:00:21.360 --> 0:00:24.720 the question of thirst. Now, if you remember, in the 0:00:24.760 --> 0:00:29.520 last episode, Rob we talked about the the biology of 0:00:29.520 --> 0:00:34.560 of thirst, anticipation of anticipation of the quenching of thirst. 0:00:34.720 --> 0:00:38.199 Because there's this interesting thing where after you drink a 0:00:38.200 --> 0:00:41.120 glass of water when you've been dehydrated, it takes some 0:00:41.280 --> 0:00:44.040 number of minutes, maybe on the order of tens of minutes, 0:00:44.479 --> 0:00:47.960 before that water actually gets absorbed through the digestive system 0:00:48.040 --> 0:00:50.600 and ends up in the blood and makes a difference 0:00:50.640 --> 0:00:55.000 systemically throughout the body. And yet you still feel that 0:00:55.000 --> 0:00:58.640 that thirst quenchiness after you have just the first class 0:00:58.640 --> 0:01:01.720 of water. You're not continue senuous lee chugging for ten 0:01:01.760 --> 0:01:05.280 to twenty minutes, at least hopefully not. But to start 0:01:05.319 --> 0:01:08.119 off today, I wanted to come back to the question 0:01:08.400 --> 0:01:12.920 of how it is that the body detects the and 0:01:13.240 --> 0:01:18.679 anticipates the coming changes in your blood and your blood osmolality, 0:01:18.880 --> 0:01:23.000 which again is the concentration of dissolved substances like mineral 0:01:23.040 --> 0:01:27.759 salts in your in your body's water content, and how 0:01:27.800 --> 0:01:32.280 it anticipates those changes to provide you that delicious feeling 0:01:32.319 --> 0:01:35.280 of having your thirst quenched by a glass of water. Now, 0:01:35.280 --> 0:01:37.640 in the previous episodes, we already talked about a few 0:01:37.680 --> 0:01:42.560 ways that the mouth and the throat might detect the 0:01:42.560 --> 0:01:45.399 the introduction of water into the body and and sort 0:01:45.400 --> 0:01:48.320 of sin signals to the brain saying hey, okay, you 0:01:48.360 --> 0:01:50.680 can put the thirst on hold for now. There there 0:01:50.680 --> 0:01:54.279 are there are soon coming changes to the body's hydration levels. 0:01:54.320 --> 0:01:56.440 And one of the ideas we talked about was the 0:01:56.480 --> 0:01:59.920 possibility that temperature plays a role, because maybe there there's 0:02:00.000 --> 0:02:03.160 some evidence that the power of water to cool the 0:02:03.240 --> 0:02:07.120 mouth and throat sends quenching signals to the brain. And 0:02:07.400 --> 0:02:11.800 also there was some evidence that rodents were using sour 0:02:12.000 --> 0:02:15.400 taste receptors in the mouth to detect the presence of water. 0:02:15.480 --> 0:02:17.760 But Rob, maybe you can sent me straight on this one. 0:02:17.840 --> 0:02:21.639 I don't think it was clear that triggering the sour 0:02:21.760 --> 0:02:25.679 taste receptors actually led to the quenching of thirst. Rather, 0:02:25.760 --> 0:02:29.680 it seemed to encourage more drinking behavior when the mouse 0:02:29.800 --> 0:02:32.680 was thirsty. Is that right, Yes, that's my understanding of 0:02:32.720 --> 0:02:35.920 these findings. But I was actually reading about um a 0:02:35.919 --> 0:02:38.800 few more studies on exactly this question of of how 0:02:38.840 --> 0:02:42.600 thirst quenching happens. What is the mechanism that leads to 0:02:42.639 --> 0:02:45.040 these changes in the brain that tell you, ah, you 0:02:45.080 --> 0:02:48.280 are thou art now quenched. So the first thing I 0:02:48.360 --> 0:02:50.240 wanted to talk about was a study that was reading 0:02:50.240 --> 0:02:53.560 about a New York Times article from eighteen by Veryy 0:02:53.760 --> 0:02:57.440 Greenwood called you get thirsty and drink, how does your 0:02:57.440 --> 0:03:00.360 brain signal you've had enough? And this is where referring 0:03:00.400 --> 0:03:03.880 to a paper that I think came up in passing 0:03:03.919 --> 0:03:07.920 in the previous episode, but it was by Vanyte Augustine 0:03:07.960 --> 0:03:13.600 at All in Nature called Hierarchical Neural Architecture underlying Thirst regulation, 0:03:14.120 --> 0:03:16.600 And this research has been looking at exactly this question 0:03:16.639 --> 0:03:19.080 we just brought up, and they confirmed that, of course, 0:03:19.120 --> 0:03:22.400 there there is a complex of neurons in the brain 0:03:22.440 --> 0:03:27.280 that appear to cease activity after a thirsty mouse drinks water. 0:03:27.440 --> 0:03:30.480 So there are some neurons that are apparently signaling that 0:03:30.760 --> 0:03:34.880 generating that thirst motivation state. But then when a roadent 0:03:34.960 --> 0:03:38.120 takes some water in through the mouth, those neurons shut up, 0:03:38.200 --> 0:03:41.480 they go quiet. So this would be the neural mechanism 0:03:41.520 --> 0:03:44.080 to register quenching. But the question is what is the 0:03:44.120 --> 0:03:50.040 direct mechanism that that leads to the changes in those neurons. Now, 0:03:50.080 --> 0:03:53.320 this New York Times article summarizes the findings as explained 0:03:53.360 --> 0:03:58.280 by the first author on that paper, Vannyte Augustine quote, Intriguingly, 0:03:58.440 --> 0:04:01.640 what these cells are responding to is not the presence 0:04:01.720 --> 0:04:06.360 of water itself. Mr Augustine said, The researchers discovered that 0:04:06.520 --> 0:04:09.880 letting a mouse take big gulps of water would spur 0:04:10.000 --> 0:04:14.240 the neurons into action, but giving it water in gel form, 0:04:14.640 --> 0:04:17.320 which had to be chewed before it could be swallowed, 0:04:17.480 --> 0:04:21.440 did not. Neither did providing water in tiny two second 0:04:21.560 --> 0:04:25.400 long SIPs, even when the animals consumed the same total 0:04:25.480 --> 0:04:29.039 amount of water. In fact, giving the mice oil to 0:04:29.120 --> 0:04:32.200 drink had just the same effect on the neurons as 0:04:32.240 --> 0:04:35.760 gulping water. So that last part is a little gross, 0:04:35.839 --> 0:04:38.560 But based on this finding, uh, it would kind of 0:04:38.560 --> 0:04:42.600 imply that a major mechanism leading these thirst neurons to 0:04:42.600 --> 0:04:45.920 to say, okay, thirst has been quenched, would have something 0:04:45.960 --> 0:04:48.720 to do with like muscular movements in the throat, the 0:04:48.800 --> 0:04:51.440 kind of gulping that you do when you're guzzling down 0:04:51.480 --> 0:04:54.200 a bunch of water really fast. But technically maybe it 0:04:54.240 --> 0:04:56.679 doesn't even have to be water. It's just any fluid 0:04:56.760 --> 0:05:00.279 that you're gulping. I mean, as humans, we don't drink 0:05:00.279 --> 0:05:02.520 a lot of just straight oil, but we do drink 0:05:02.520 --> 0:05:05.200 a lot of things that are that are to varying 0:05:05.200 --> 0:05:09.400 degrees removed from from from you know, from from just 0:05:09.480 --> 0:05:13.800 a neutral water. Uh So this would make sense, right, 0:05:13.920 --> 0:05:16.880 But if you if you hydrate yourself in some other ways, 0:05:16.880 --> 0:05:19.560 so like the examples that you say, consuming water in 0:05:19.720 --> 0:05:22.719 gel form where you can't like gulp it down, really 0:05:23.440 --> 0:05:26.640 that still hydrates you, but that apparently does not lead 0:05:26.720 --> 0:05:30.719 to this immediate quinching signal in the brain. Similarly with 0:05:30.839 --> 0:05:34.719 drinking water in very small, isolated SIPs. I guess in 0:05:34.760 --> 0:05:38.839 those cases you would eventually hydrate yourself and your thirst 0:05:38.920 --> 0:05:41.880 will eventually go away, But it will be more likely 0:05:41.920 --> 0:05:45.960 that your body has to just become systemically hydrated before 0:05:46.120 --> 0:05:50.960 the thirst goes away. It's not that sudden quinching reward feeling. Now, 0:05:51.000 --> 0:05:54.400 there was an interesting detail offered here about reasons that 0:05:54.480 --> 0:05:57.240 the body might need to have this reaction where we 0:05:57.360 --> 0:06:00.560 turn off thirst very quickly after getting a drink, like 0:06:01.160 --> 0:06:04.520 why not just wait for your blood osmlality to reach 0:06:04.600 --> 0:06:08.279 the ideal level. Well, in previous episodes, we we talked 0:06:08.279 --> 0:06:10.359 about one reason for this, which is that you know, 0:06:10.440 --> 0:06:12.960 if you actually did have to wait for your your 0:06:13.000 --> 0:06:15.720 body's water content to get all leveled out right before 0:06:15.800 --> 0:06:19.080 your thirst went away, you might you might like kill 0:06:19.200 --> 0:06:22.359 yourself drinking gallons and gallons of water because you know 0:06:22.440 --> 0:06:24.440 over the course of the tens of minutes that it 0:06:24.480 --> 0:06:27.839 takes for this change to to take hold. But there's 0:06:27.839 --> 0:06:29.920 another reason one of the authors of this paper brings 0:06:30.000 --> 0:06:33.200 up that's in this Greenwood article in the Times. Quote, 0:06:33.400 --> 0:06:36.520 aside from the specter of water intoxication, there are good 0:06:36.520 --> 0:06:40.160 reasons to drink only the minimum amount necessary when an 0:06:40.160 --> 0:06:43.599 animal lowers its head to drink, dr Oka speculated, and 0:06:43.680 --> 0:06:48.320 that's Dr Yukioka. Uh, it's in quite a vulnerable position. Quote. 0:06:48.360 --> 0:06:51.120 If you double the time of ingestion, that should double 0:06:51.200 --> 0:06:54.560 the risk of being prey. He said, Uh. And I 0:06:54.600 --> 0:06:56.680 thought that was interesting too. I mean, I think it 0:06:56.800 --> 0:06:59.240 is true that in the natural environment, as we brought 0:06:59.279 --> 0:07:02.080 up in the previous episode. Going for water is often 0:07:02.080 --> 0:07:06.000 putting yourself in a vulnerable position, you know, maybe um, 0:07:06.040 --> 0:07:09.720 exposing yourself from hiding or shelter and sort of turning 0:07:09.760 --> 0:07:13.600 your attention away from scanning your surroundings. Yeah. I mean 0:07:14.680 --> 0:07:17.200 in many cases too, they the access point to the 0:07:17.240 --> 0:07:20.080 water might not provide much in the way of cover 0:07:20.200 --> 0:07:24.360 for smaller animals, and then for larger animals there may 0:07:24.400 --> 0:07:28.360 be you know, bodily positions they have to get into 0:07:28.080 --> 0:07:32.560 to drink that put them in a greater state of vulnerability, 0:07:32.880 --> 0:07:35.840 Like I'm thinking of of a drafte for instance. The 0:07:36.080 --> 0:07:40.440 draffe of course is a pretty formidable animal. Uh, but 0:07:40.440 --> 0:07:43.920 but still there's a certain awkwardness present when it actually 0:07:43.920 --> 0:07:47.200 has to drink water. Sorry, I just started thinking about 0:07:47.240 --> 0:07:52.040 game or fuel. Um, yeah, this is this says. I 0:07:52.080 --> 0:07:54.680 have no research to back this up. There's just observational 0:07:55.080 --> 0:07:58.080 material for me. But I think everyone knows that I 0:07:58.400 --> 0:08:02.920 enjoy watching the squirrels and um, we have a bird 0:08:02.920 --> 0:08:07.600 bath outside, uh, near our feeders, and the bird bath 0:08:07.760 --> 0:08:11.280 is positioned right up against the fence, and the squirrels 0:08:11.360 --> 0:08:14.160 drink from that all the time. But I wonder how 0:08:14.240 --> 0:08:16.200 much I wonder how much of that is that they're 0:08:16.240 --> 0:08:21.920 able to drink from the bird bath while essentially remaining 0:08:21.920 --> 0:08:24.920 in a vertical position attached to the to the fence, 0:08:25.840 --> 0:08:27.920 like they don't have to, you know, go across the clearing. 0:08:28.160 --> 0:08:30.800 They have I guess, pretty good cover for a squirrel. 0:08:30.840 --> 0:08:33.840 Those squirrels are bold in other ways that, you know, 0:08:33.880 --> 0:08:36.520 make you think that they're they're less concerned, or they're 0:08:37.080 --> 0:08:39.679 or they're in control of the situation as far as 0:08:39.679 --> 0:08:42.439 potential predators go. So, if you happen to have sitter 0:08:42.559 --> 0:08:46.000 squirrels and rover squirrels, your bird bath is positioned in 0:08:46.040 --> 0:08:48.199 such a way that even the sitter squirrels could could 0:08:48.240 --> 0:08:51.160 get to it, I guess so. But then, yeah, I 0:08:51.160 --> 0:08:52.880 don't know. I'd be interested to hear what anyone else 0:08:52.920 --> 0:08:56.280 out there has observed with their squirrels and drinking water 0:08:56.360 --> 0:09:00.880 from bird baths and other water water sources. They seem 0:09:00.920 --> 0:09:02.679 to like one thing versus the other. I don't know. 0:09:02.880 --> 0:09:05.360 They certainly drink more water than my cat. I'll give 0:09:05.360 --> 0:09:09.120 them that well. Anyway. There was another article from the 0:09:09.200 --> 0:09:11.520 very next year, also in the New York Times, also 0:09:11.600 --> 0:09:14.720 by Greenwood, covering follow up research from some of the 0:09:14.760 --> 0:09:19.760 same scientists. So this was published May nineteen just called 0:09:19.760 --> 0:09:24.040 the Neurobiology of Thirst, and this is summarizing a study 0:09:24.040 --> 0:09:27.360 published in twenty nineteen in the journal Neuron where the 0:09:27.480 --> 0:09:30.440 authors oh again. The first author on this one was 0:09:30.840 --> 0:09:35.319 Vanite Augustine and it was called Temporally and spatially distinct 0:09:35.520 --> 0:09:40.120 thirst Satiation Signals UM and the authors here found that 0:09:40.800 --> 0:09:43.880 the pleasure we get from drinking when thirsty is once 0:09:43.880 --> 0:09:47.480 again not directly related to hydration. It is a reward 0:09:47.520 --> 0:09:51.200 pathway separated by both time and space from the body's 0:09:51.280 --> 0:09:56.679 hydration and osmolality monitoring mechanisms. And one of the major 0:09:56.760 --> 0:10:00.480 findings in this paper is that though drinking water is 0:10:00.600 --> 0:10:05.000 associated with a dopamine release, this this is a typical 0:10:05.040 --> 0:10:08.480 signal that the brain is expecting a reward. Right you know, 0:10:08.679 --> 0:10:11.600 things that you want, you want to get and feel 0:10:11.640 --> 0:10:14.360 good when you get them. That that's often that involves 0:10:14.360 --> 0:10:18.240 a dopamine release. But the feeling of rewards in the 0:10:18.280 --> 0:10:22.280 brain here is apparently not tied to becoming hydrated after 0:10:22.400 --> 0:10:26.920 being dehydrated, but specifically to the act of drinking water 0:10:27.040 --> 0:10:30.200 through the mouth. So if you're dehydrated and then you 0:10:30.240 --> 0:10:33.640 suddenly receive water through an I V or even via 0:10:33.679 --> 0:10:37.680 a direct injection into the stomach. Your thirst will eventually 0:10:37.720 --> 0:10:40.800 go away after your body adjusts to the new fluid levels, 0:10:41.200 --> 0:10:44.920 but you won't get that feeling of reward satisfaction or 0:10:45.000 --> 0:10:49.679 the corresponding dopamine release. Those come specifically from the activity 0:10:49.720 --> 0:10:52.920 of drinking, the gulping of water through the mouth. And 0:10:53.080 --> 0:10:54.920 picking up on this, I was actually looking at one 0:10:54.960 --> 0:10:57.959 more paper that had an interesting finding I wanted to mention. 0:10:58.360 --> 0:11:00.840 This other one was a little leer. This was from 0:11:01.920 --> 0:11:06.920 published in Nature called thirst neurons anticipate the homeostatic consequences 0:11:06.920 --> 0:11:09.679 of eating and drinking, and this is by Zimmerman at 0:11:09.679 --> 0:11:14.040 All and this study found, among other things, a dual 0:11:14.280 --> 0:11:19.400 track monitoring system for thirst management, so along the lines 0:11:19.480 --> 0:11:21.960 we've already been talking about it. It found that if 0:11:22.000 --> 0:11:24.440 you take mice and you give them some salt and 0:11:24.480 --> 0:11:29.800 make them thirsty, drinking water rapidly inhibits neurons in a 0:11:29.880 --> 0:11:33.240 region of the brain called the sub formical organ or SFO, 0:11:33.400 --> 0:11:36.800 and that leads to thirst quenching. And of course this 0:11:36.880 --> 0:11:40.000 is before there is any notable change in blood osmlality. 0:11:40.160 --> 0:11:43.280 But it also found that if you take these thirsty 0:11:43.360 --> 0:11:47.280 mice and you give them very salty water and and 0:11:47.480 --> 0:11:50.400 the opportunity to drink it. They will drink it, and 0:11:50.440 --> 0:11:54.400 initially they will gulp it down and it will inhibit 0:11:54.440 --> 0:11:57.560 the sf O neurons and apparently quench thirst just like 0:11:57.640 --> 0:12:01.640 the fresh water. But the quenching doesn't last for very long, 0:12:02.120 --> 0:12:05.360 and they right quote. This initial decline was reversed after 0:12:05.400 --> 0:12:10.040 approximately one minute. This indicates that the rapid anticipatory response 0:12:10.080 --> 0:12:13.560 to drinking has at least two components, an immediate signal 0:12:13.640 --> 0:12:17.720 that tracks fluid ingestion and a delayed signal that reports 0:12:17.720 --> 0:12:22.600 on fluid tonicity, possibly generated by an esophageal or gastric 0:12:22.640 --> 0:12:26.400 osmo sensor. So if you put all of this together, 0:12:26.600 --> 0:12:29.920 it seems like you've got at least three different time 0:12:29.960 --> 0:12:33.959 dependent levels of of sort of the body's quench watch uh. 0:12:34.000 --> 0:12:35.760 And so you put them all together, and you've got 0:12:35.800 --> 0:12:39.319 one system that's like are you gulping fluid? If you are, 0:12:39.400 --> 0:12:42.840 oh that's very good, very good, thou art quenched. But 0:12:42.880 --> 0:12:45.880 then there's a second system on a slight delay from 0:12:45.920 --> 0:12:49.280 that one, roughly one minute of delay in mice, It's like, 0:12:49.800 --> 0:12:53.600 wait a second, what exactly was that you were just gulping. 0:12:53.880 --> 0:12:57.920 Was that oil or was that super salty water? You know, what, 0:12:57.920 --> 0:12:59.720 what are you trying to pull? And if it well, 0:12:59.760 --> 0:13:03.520 if it was not good fresh water, then it will cancel, 0:13:03.840 --> 0:13:07.840 cancel the quench and return the thirst. And then finally, 0:13:07.880 --> 0:13:11.439 I guess there's just the direct blood volume and osmalality monitoring, 0:13:11.480 --> 0:13:13.960 which is on a much greater delay than the other two. 0:13:14.440 --> 0:13:17.280 Uh So, first of all, reminder, if anyone else, if 0:13:17.280 --> 0:13:19.520 anyone is interested in the whole drinking saltwater thing, we 0:13:19.559 --> 0:13:22.920 did a whole episode on drinking saltwater a while back. 0:13:23.480 --> 0:13:25.319 You should be able to find that in the archives. 0:13:25.679 --> 0:13:27.680 Not a good idea was It was one of the 0:13:27.720 --> 0:13:31.440 main findings there. But the the other thing, I think, 0:13:31.480 --> 0:13:33.120 and we've kind of we've kind of touched on this 0:13:33.120 --> 0:13:36.680 a little bit already, but um, you know, it would 0:13:36.720 --> 0:13:38.640 be a mistake to think of like, okay, it's just 0:13:38.720 --> 0:13:42.080 you know, what's drinking water, water in water out. Um, 0:13:42.120 --> 0:13:44.960 you know, even if you you then acknowledge, okay, well 0:13:45.000 --> 0:13:46.520 you know the levels have to be just right. But 0:13:46.559 --> 0:13:49.839 it's it's more than that. It's not like organisms just 0:13:50.080 --> 0:13:52.640 one day we're like, hey, there's water we can drink 0:13:52.679 --> 0:13:54.680 that we should use this to our advantage. Now, like 0:13:54.760 --> 0:13:58.439 we are of water, so it's like water in am 0:13:58.520 --> 0:14:02.920 water if all of doubt of things in water, um, etcetera. 0:14:03.000 --> 0:14:05.080 So it's it makes sense that there would be a 0:14:05.120 --> 0:14:08.920 more complex relationship with multiple triggers that uh you know 0:14:09.000 --> 0:14:12.839 that that we're still trying to understand. Yeah, I mean, 0:14:13.000 --> 0:14:15.120 as we said at the very beginning, you you are 0:14:15.240 --> 0:14:18.400 the direct descendant of creatures that long ago lived in 0:14:18.440 --> 0:14:21.120 the ocean and all of your ancestors, just like you 0:14:21.280 --> 0:14:24.440 brought the ocean with you onto land, the ocean is 0:14:24.480 --> 0:14:27.880 now inside your skin. Yes. Oh, and before I wrap up, 0:14:28.080 --> 0:14:32.720 this last study I mentioned also documents interesting evidence for 0:14:32.880 --> 0:14:36.440 the the oral cooling mechanism of thirst quenching that I 0:14:36.480 --> 0:14:39.520 brought up in the previous episode. So the authors here 0:14:39.600 --> 0:14:42.680 say that quote we found that are playing cold but 0:14:42.920 --> 0:14:47.240 not room temperature metal to the oral cavity of awake 0:14:47.480 --> 0:14:52.880 thirsty mice was sufficient to rapidly inhibit SFO neurons. Thus, 0:14:53.080 --> 0:14:58.040 temperature dependent modulation of SFO neurons may explain the enigmatic 0:14:58.040 --> 0:15:02.680 connection between oral cooling and thirst, including why thirsty rodents 0:15:02.680 --> 0:15:06.920 will avidly lick cold metal and humans report that's sucking 0:15:06.960 --> 0:15:11.800 on ice chips rapidly relieves thirst. That's interesting. I hadn't 0:15:11.800 --> 0:15:15.920 really thought about that with sucking on ice chips, though obviously, 0:15:16.000 --> 0:15:17.760 I mean that's I think that's something we all do 0:15:17.840 --> 0:15:22.000 if we have access to iced drinks. Of course. The 0:15:22.040 --> 0:15:24.360 thing with with ice, of course, is that ice melts 0:15:24.360 --> 0:15:27.880 in your mouth as well and actually serves to hydrate you. Right, 0:15:27.920 --> 0:15:30.840 But that the the cooling effect of having the ice 0:15:30.880 --> 0:15:34.440 in the mouth may provide a level of of thirst 0:15:34.520 --> 0:15:38.360 quenching sensation that goes beyond the actual amount of water 0:15:38.520 --> 0:15:41.320 you're taking in from that ice. This gives me a 0:15:41.320 --> 0:15:46.280 great idea, um so showrunners and so forth, of the Witcher. 0:15:46.320 --> 0:15:48.480 If you're listening, I would love to see a scene 0:15:48.480 --> 0:15:52.760 where Henry Cavill's uh Witcher character share some wisdom and 0:15:52.800 --> 0:15:56.320 he's like, sometimes when when I'm thirsty, I just have 0:15:56.320 --> 0:15:59.480 a good lick of my sword takes you know. It 0:15:59.480 --> 0:16:01.280 would be gre Haven scene everyway. It's just kind of 0:16:01.280 --> 0:16:03.920 licking is the blade of his sword. I've never heard 0:16:04.000 --> 0:16:08.440 this before that apparently thirsty, thirsty rodents will lick cold metal. 0:16:08.560 --> 0:16:12.520 But yeah, yeah, but and it's good enough for mice, 0:16:12.600 --> 0:16:15.040 it's good enough for the Wincher, I think all Gerrold 0:16:15.120 --> 0:16:17.720 is just gonna that's that's how you cut your tongue, buddy, 0:16:17.880 --> 0:16:19.880 That's how you cut your tongue. Oh, you know, it 0:16:19.920 --> 0:16:22.680 reminds me of brom Stoker's Dracula. We have that wonderful 0:16:22.680 --> 0:16:28.080 scene where Gary Oldman's elderly Dracula licks the blood from 0:16:28.120 --> 0:16:32.280 the straight razor. See, he was thirsty and he quenched 0:16:32.320 --> 0:16:35.760 the thirst, but also hopefully the blade was cold enough 0:16:35.880 --> 0:16:37.960 that that also had an effect on him. Well, I 0:16:38.000 --> 0:16:40.800 guess after all these studies we looked at on on 0:16:40.800 --> 0:16:44.360 on the quenching mechanism, I'm wondering, so the two main 0:16:44.720 --> 0:16:48.560 different ones have emerged. One is the oral cooling mechanism 0:16:48.680 --> 0:16:51.040 and the other is the gulping mechanism. You know, the 0:16:51.280 --> 0:16:53.880 muscular movements in the throat is you're swallowing large amounts 0:16:53.920 --> 0:16:56.440 of water. Uh. And I'm I guess I'm not sure 0:16:56.440 --> 0:17:00.000 if these two different explanations are competing or if they're complementary. 0:17:00.080 --> 0:17:02.440 Maybe they both play a role in in regulating these 0:17:02.640 --> 0:17:04.880 thirst neurons in the s f O. I'm not sure 0:17:09.680 --> 0:17:14.000 than now, given all the things we've discussed about the 0:17:14.040 --> 0:17:19.440 complexity of thirst, sensations and water acquisition by various organisms. 0:17:19.440 --> 0:17:22.919 I thought it might be um be interesting to to 0:17:22.960 --> 0:17:25.679 look at a couple of examples that, in different ways 0:17:26.200 --> 0:17:31.639 seem to hijack mechanisms of related to thirst and our 0:17:31.680 --> 0:17:34.920 relationship with water, not only ours, but also some other 0:17:35.040 --> 0:17:39.119 organisms for the benefit of a life form, not the 0:17:39.160 --> 0:17:42.959 life form that is uh that is potentially thirsty, but 0:17:43.400 --> 0:17:47.240 a life form that is um uh that is hijacking 0:17:47.280 --> 0:17:51.720 that organism, uh, such as a parasite or a virus. 0:17:51.720 --> 0:17:55.040 Oh interesting, so uh. The first one I want to 0:17:55.119 --> 0:17:58.400 mention here is is one that definitely affects humans, and 0:17:58.480 --> 0:18:01.880 that is raybies. Now, I imagine I think everyone has 0:18:01.880 --> 0:18:04.600 heard of rabies, if not buckling, because I'm gonna share 0:18:04.680 --> 0:18:07.240 a little bit though. This is obviously a topic that 0:18:07.760 --> 0:18:09.480 you know, we could really bust out if we wanted 0:18:09.520 --> 0:18:12.800 to and give a full episode treatment. But even if 0:18:12.800 --> 0:18:15.919 you're just vaguely familiar with rabies, uh, you know, you 0:18:16.000 --> 0:18:18.520 might not grasp the full danger and horror of this 0:18:18.600 --> 0:18:22.280 particular zoonotic viral disease. I think a while back I've 0:18:22.320 --> 0:18:25.639 read at least somebody making the case that rabies is 0:18:26.000 --> 0:18:30.040 a contender for like the worst disease known. Yeah, it 0:18:30.200 --> 0:18:34.000 is pretty horrifying and for a lot of people in 0:18:34.280 --> 0:18:37.040 UM in the world, particularly and let's let's say the 0:18:37.160 --> 0:18:42.400 United States, you're lucky enough to to live largely removed 0:18:42.440 --> 0:18:45.320 from it. Um. I think that the US is sometimes 0:18:45.320 --> 0:18:50.400 class of classified as being free of canine rabies. Now 0:18:50.400 --> 0:18:53.119 there are still cases of canine rabies that pop up, 0:18:53.119 --> 0:18:56.199 and there are deaths that occur, but but not at 0:18:56.240 --> 0:18:57.960 the same rate as as other parts of the world 0:18:57.960 --> 0:19:01.200 where the problem has not been contained as well. So 0:19:01.359 --> 0:19:04.720 it's uh. Rabies is caused by the virus Lissa virus, 0:19:04.760 --> 0:19:08.280 which essentially means rage poison. It's named for the Greek 0:19:08.320 --> 0:19:13.400 goddess Lissa, the goddess of rage, fury, and rabies Uh, 0:19:13.480 --> 0:19:17.920 the daughter of Nicks, sprung from the blood of Laurnus 0:19:18.240 --> 0:19:21.240 um and Uh, and she pops up in different tales, like, 0:19:21.280 --> 0:19:24.640 for instance, that the urging of hera, she inflicts madness 0:19:24.640 --> 0:19:27.919 on Heracles, and in some tellings she's also involved in 0:19:27.960 --> 0:19:31.440 the punishment of the hunter Acteon, who's torn apart by 0:19:31.480 --> 0:19:34.480 his own mad hunting dogs. And in memory Serves, there 0:19:34.520 --> 0:19:38.320 are some interesting treatments of this UH. This latter tale 0:19:38.320 --> 0:19:42.080 in art I think he he looked at a god 0:19:42.359 --> 0:19:44.800 or something to that effect. You know, you don't have 0:19:44.840 --> 0:19:46.840 to do much to get to torn apart by dogs 0:19:46.880 --> 0:19:50.280 when you're dealing with the Greek pantheon. Yeah. I don't 0:19:50.320 --> 0:19:53.400 remember all the details, but I think he makes Artemis 0:19:53.440 --> 0:19:56.280 angry for some reason, and then he's a hunter. But 0:19:56.359 --> 0:20:00.040 then he's transformed into the quarry like he's trying it 0:20:00.080 --> 0:20:02.119 is formed into a stag or something, and then his 0:20:02.160 --> 0:20:05.439 own hunting dogs hunt thatch. Right, there's some transformation involved 0:20:05.480 --> 0:20:08.600 there as well. So humans have been exposed to rabies 0:20:08.600 --> 0:20:11.639 for a very long time. It's um. It's thought that 0:20:11.680 --> 0:20:16.280 it probably originated in Old world bats and especially flourished 0:20:16.359 --> 0:20:20.199 during the heyday of of dog domestication. So it is, 0:20:20.560 --> 0:20:24.439 you know, it is. It is definitely tied to the 0:20:24.480 --> 0:20:28.879 canine world. According to the History of Rabies in the 0:20:28.920 --> 0:20:33.919 Western Hemisphere by Velasco Villa at All, published in Anti 0:20:34.000 --> 0:20:38.600 Viral Research UM, the earliest record of a disease affecting 0:20:39.000 --> 0:20:43.520 humans that's consistent with rabies and associated with dogs is 0:20:43.560 --> 0:20:48.600 found in the Eshnuna cuneiform law tablets in ancient Mesopotamia 0:20:48.720 --> 0:20:54.120 dating back to the eighteenth through nineteenth centuries b c. Wow, Yeah, 0:20:54.160 --> 0:20:57.040 and I believe memory served it. It concerns like laws 0:20:57.600 --> 0:21:01.080 concerning um dogs biting people, like if you you have 0:21:01.119 --> 0:21:03.720 a dog and it bites somebody. And of course we 0:21:03.760 --> 0:21:08.920 have other references to UH to either cases that seem 0:21:09.000 --> 0:21:11.200 like they could be rabies or we feel pretty strongly 0:21:11.480 --> 0:21:15.680 are referring to rabies. Aristotle wrote seem to have wrote 0:21:15.680 --> 0:21:19.439 of it in three thirty b c. Quote dogs suffer 0:21:19.560 --> 0:21:23.200 from the madness. This causes them to become very irritable, 0:21:23.480 --> 0:21:28.280 and all animals they bite become diseased. Democratusts and Hippocrates 0:21:28.359 --> 0:21:31.600 also wrote of it as well, And there are comparisons 0:21:31.800 --> 0:21:35.399 to raging dogs in the Iliad that it seems like 0:21:35.440 --> 0:21:37.720 maybe you're less certain that this is referring, because of 0:21:37.760 --> 0:21:39.840 course a dog can rage. I guess it doesn't have 0:21:39.920 --> 0:21:43.159 to be rabbit. But they are also mentions of the 0:21:43.240 --> 0:21:48.200 dog star Ryan exerting a malignant influence on human health 0:21:49.480 --> 0:21:53.080 and UH and rabies is just a terrible disease, especially 0:21:53.119 --> 0:21:56.439 when you really get into what it can do to 0:21:57.160 --> 0:21:59.680 an organism and what it can do to human being. UH. 0:21:59.760 --> 0:22:04.600 To day, it's vaccine preventable, and the vaccines keep improving, 0:22:05.000 --> 0:22:09.440 but once clinical symptoms appear, it is fatal. According to 0:22:09.480 --> 0:22:15.480 the World Health Organization, in cases domestic dogs are responsible 0:22:15.520 --> 0:22:18.520 for spreading it to humans. Again, in the United States, 0:22:18.960 --> 0:22:23.800 it is effectively we're effectively canine rabies free, though you 0:22:23.880 --> 0:22:27.159 will still find cases that occur and deaths that occur. 0:22:27.600 --> 0:22:31.400 So um, it's it's still possible, but it is largely 0:22:31.480 --> 0:22:34.679 under control. In other parts of the world it's not 0:22:34.760 --> 0:22:36.720 the case. And so um, you know, this is all 0:22:36.760 --> 0:22:40.920 a great reminder why it is important to get your 0:22:40.960 --> 0:22:46.120 dog rabies vaccine and to also get yourself immunized if 0:22:46.160 --> 0:22:50.240 you come into contact with the disease, and that time 0:22:50.359 --> 0:22:54.040 is very important. They're right, Yeah, So that the incubation 0:22:54.080 --> 0:22:57.040 period for rabies is typically two to three months, but 0:22:57.200 --> 0:23:00.280 may vary from one week to a year. And I 0:23:00.280 --> 0:23:03.080 think it depends on like the viral load on you know, 0:23:03.119 --> 0:23:07.239 being introduced into your body and some other factors. And 0:23:07.280 --> 0:23:09.359 then there are two forms of the disease that are 0:23:09.400 --> 0:23:12.240 possible in humans. So once you know this virus is 0:23:12.280 --> 0:23:16.520 in your system, uh. One version is paralytic rabies. This 0:23:16.560 --> 0:23:19.600 only occurs in about twenty of cases, and it consists 0:23:19.600 --> 0:23:25.560 of gradual muscle paralyzation, coma, and death. It's often misdiagnosed, 0:23:25.760 --> 0:23:29.080 but again, like twenty of cases, this is what occurs. 0:23:29.600 --> 0:23:34.200 The other, however, is the the the the incarnation of 0:23:34.200 --> 0:23:37.879 of rabies that certainly brings to mind these ideas of 0:23:37.920 --> 0:23:41.520 strange curses from the gods, you know, the really horrible stuff, 0:23:41.640 --> 0:23:50.040 and that's furious rabies. Symptoms here include hyperactivity, excitable behavior, hydrophobia, 0:23:50.280 --> 0:23:54.600 the fear of water, and sometimes aerophobias, well, fear of 0:23:54.720 --> 0:23:57.520 drafts of fresh air or you know, blasts of air, 0:23:57.600 --> 0:24:01.359