The cellular basis of distinct thirst modalities

Abstract

Fluid intake is an essential innate behavior mainly caused by two distinct types of thirst [1][2][3] . Increased blood osmolality induces osmotic thirst that drives animals to consume pure water. Conversely, the loss of body fluid induces hypovolemic thirst in which animals seek both water and minerals (salts) to recover blood volume. Circumventricular organs (CVOs) in the lamina terminalis (LT) are critical sites for sensing both types of thirst-inducing stimuli [4][5][6] . However, how different thirst modalities are encoded in the brain remains unknown. Here, we employed stimulus to cell-type mapping using single-cell RNA-seq (scRNA-seq) to determine the cellular substrate underlying distinct types of thirst. These studies revealed diverse excitatory and inhibitory neuron types in each CVO structure. Among them, we show that unique combinations of neuron types are activated under osmotic and hypovolemic stresses. These results elucidate the cellular logic underlying distinct thirst modalities. Furthermore, optogenetic gain-of-function in thirst-modalityspecific cell types recapitulated water-specific and non-specific fluid appetite caused by the two distinct dipsogenic stimuli. Taken together, this study demonstrates that thirst is a multimodal physiological state, and that different thirst states are mediated by specific neuron types in the mammalian brain.In the mammalian brain, fluid imbalance is detected by LT CVOs, the sensory organs of the brain that lack the normal blood-brain barrier 7 . The subfornical organ (SFO) and organum vasculosum lamina terminalis (OVLT) are the forebrain CVOs that sense internal fluid status and regulate drinking behavior through their downstream brain sites. The majority of excitatory neurons in these CVOs are activated under dehydration, and acute stimulation of Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:

Enhanced recovery of single-cell RNA-sequencing reads for missing gene expression data

“…The recovery of this gene revealed that Glut6 MnPO is likely the heat activated neuron type as it is labeled by all three warmth markers (Ptger3, Bdnf, Pacap). Furthermore, this analysis also revealed that three neuron classes Glut1 MnPO , Glut2 MnPO , and Glut3 MnPO are likely the thirst state encoding neurons as they are labeled by all thirst markers as well as Etv1 that was recently shown to exclusively label thirst activated neuron classes in related lamina terminalis nuclei 11 . Finally, the markers for cold and ingestion activated neurons appear to exclusively label a single cell type each (Glut4 MnPO for cold, Gaba1 MnPO for ingestion) that collectively suggests a clear mapping of previously uncovered physiological functions to the underlying neuron classes (Extended Fig.…”

“…Furthermore, recent work has demonstrated that the majority of intronic reads stem from aberrant priming of transcripts from intronic poly-A tracts emphasizing the importance of not discarding these data 16,17 . Finally, a few studies have resorted to manually fixing individual loci providing a local fix to a global problem 8,11 . Here, we have undertaken a systemic effort to provide genome wide optimized transcriptomic references for mouse and human reference transcriptomes and outlined a general strategy to easily achieve the same for any genome of interest.…”

“…Droplet-based single-cell RNA-sequencing methods such as Dropseq and 10x Genomics platforms have dramatically lowered the cost and improved the throughput of single-cell gene expression profiling. These advances have thereby widely democratized the discovery of new cell types and states 6–8 , delineation of developmental mechanisms 9 and cellular basis of disease 10 as well as mapping of behavioral and physiological functions to distinct cell types 11,12 . The scalability of such methods however comes with a few important limitations.…”

Gliotransmission of D-serine promotes thirst-directed behaviors inDrosophila

“…Osmosensory neurons in the subfornical organ (SFO) and organum vasculosum (OVLT) of the lamina terminalis (LT) of the mammalian forebrain respond directly and indirectly to changes in plasma osmolality and blood volume/pressure, via hormones such as Angiotensin II (Bourque, 2008; Fitzsimons, 1998; Pool et al, 2020). These neurons then directly or indirectly release compensatory neuropeptide/hormone signals like Vasopressin/anti-diuretic hormone which promotes bodily responses to reduce water loss and restore blood pressure, and behavioral responses to restore fluid balance (Augustine et al, 2020; Johnson and Thunhorst, 1997; Rolls, 1971; Zimmerman et al, 2017).…”

Cannabinoids regulate an insula circuit controlling water intake

“…The brain perceives internal thirst states and subsequently drives drinking behavior to maintain bodily fluid homeostasis [1][2][3][4][5][6]. Imaging studies in humans and rodents suggest that the insular cortex (IC) responds to thirst-linked states by increasing its global neural activity [7][8][9].…”