Biology subjects

Lemon, C. H.

Publications and source records attributed to Lemon, C. H..

4 recordsLinked to original sources

bioRxiv2026

Temperature effects on taste preferences are influenced by TRPM8

Taste perception is influenced by stimulus and oral temperature. Change in oral temperature modulates trigeminal neurons. Whether trigeminal thermal sensing interacts with taste is unknown. Here we studied temperature influences on mouse taste preferences and how they could change following silencing of TRPM8 (transient receptor potential melastatin 8) - a thermoreceptor supporting cool and warm temperature coding by trigeminal neurons. Female and male TRPM8 gene deficient and C57BL/6J (B6) control mice (n = 69) entered thermolickometry tests where they sampled taste solutions at cool (15{degrees}C) and warm (30{degrees}C) temperatures during brief-access (10-sec long) exposure trials, which capture oral sensory/tongue control of licking behavior. Taste solutions included innately avoided bitter quinine (0.03 and 0.3 mM) and preferred sugars (sucrose or glucose, 100 and 500 mM). Mice were respectively maintained under water restriction or water-replete conditions during quinine and sugar tests, which were conducted separately. Analyses revealed that 15{degrees}C enhanced, while 30{degrees}C reduced, licks to quinine in both B6 and TRPM8 deficient mice, which responded similarly (p > 0.05). In contrast, licks to static concentrations of sugars trended towards enhancement by 30{degrees}C, compared to 15{degrees}C, in male B6 mice but were suppressed, and inhibited, by 30{degrees}C (p < 0.05) in male TRPM8 deficient mice. This result agrees with prior studies that show warmth normally facilitates sweetness and that 30{degrees}C stimulation of oral tissues becomes anomalously aversive in TRPM8 deficient mice. These data provide initial evidence that TRPM8 thermosensory influences interact with sugar taste preferences, which may reflect a trigeminal-taste cross-modal phenomenon.

neuroscience↗

bioRxiv2025

Parabrachial Calca neurons influence aversive and appetitive taste function

The parabrachial (PB) nucleus participates in taste processing and integration with other senses. PB neurons that express the Calca gene support sensory-integrative responses, albeit only limited data have addressed their influence on taste. Here we studied how chemogenetic dampening of PB-Calca neurons impacted mouse orosensory preferences for diverse taste stimuli in brief-access fluid exposure tests, which capture oral sensory/tongue control of licking behavior. Intracranial delivery of Cre-dependent viruses in female and male CalcaCre/+ mice induced expression of the inhibitory designer receptor hM4Di:mCherry (hM4Di mice) or fluorophore mCherry alone (mCherry mice) in PB-Calca neurons. Several weeks later, hM4Di and mCherry mice entered brief-access tests where they could lick taste solutions on discrete seconds-long trials. Stimuli included the behaviorally avoided, but functionally different, bitter taste stimuli quinine (0 [water], 0.1, 0.3, and 1.0 mM) and cycloheximide (0, 0.001, 0.003, and 0.01 mM), and the appetitive sugar sucrose (0, 100, 300, 500, and 1000 mM). Both hM4Di and mCherry mice received the hM4Di ligand clozapine-N-oxide (CNO, 5 mg/kg, i.p.) prior to daily tests performed by blinded experimenters. With CNO, hM4Di mice displayed greater average licking (i.e., less avoidance) of quinine (p < 0.05), but not cycloheximide (p > 0.3), than mCherry mice, implying PB-Calca neurons variably influence orosensory responses across bitter stimuli. Moreover, male hM4Di mice selectively showed reduced mean licking preferences for sucrose under CNO (p < 0.05). These data suggest that PB-Calca neurons participate in both aversive and appetitive taste-guided behaviors, with their role in appetitive taste dependent on sex.

neuroscience↗

bioRxiv2022

Diverse thermosensory receptors and neurons mediate the neural coding of oral cooling in the mouse trigeminothalamic tract

Different sets of peripheral and medullary trigeminal neurons respond across a cooling gradient applied to intraoral skin. Here we applied electrophysiology to anesthetized mice to study if different types of cool-driven trigeminothalamic neurons convey oral cooling information to the thalamus. We monitored spiking responses to oral stimulation with cold ([≤]13{degrees}C), cool (21{degrees}C to 28{degrees}C), neutral (35{degrees}C), and warm/hot ([≥]40{degrees}C) water in single trigeminal nucleus caudalis (Vc) neurons physiologically tested for projections to the thalamus. We also recorded oral thermal responses from Vc neurons in mice gene deficient for the cooling and menthol receptor TRPM8 to study afferent mechanisms of central oral thermosensory activity. We found that thalamic-projecting Vc neurons that respond to oral cooling comprise heterogeneous cell types. These cell types showed unique temporal response kinetics across cool and cold temperatures, with tuning to select ranges of a cooling gradient. The combined thermal activity of multiple, differently tuned types of trigeminothalamic cooling neurons offered greater contrast between cold, cool, and warm temperatures in multivariate analysis than the responses of the individual neural types alone, agreeing with a neural population code for cooling information. Compared to control, TRPM8 deficient mice demonstrated a loss of Vc neurons tuned to mild oral cooling, but maintained Vc cells responsive to intense cold. Notably, distinctions between Vc population responses to mild cool and warm temperatures were impaired in TRPM8 deficient mice, suggesting a role for TRPM8 in oral warmth recognition. Diverse receptors and neurons mediate oral cooling signals carried by the trigeminothalamic pathway.

neuroscience↗

bioRxiv2021

TRPV1-lineage somatosensory fibers communicate with taste neurons in the mouse parabrachial nucleus

Trigeminal neurons supply somatosensation to craniofacial tissues. In mouse brain, ascending projections from medullary trigeminal neurons arrive at taste neurons in the autonomic parabrachial nucleus, suggesting taste neurons participate in somatosensory processing. However, the genetic cell types that support this convergence were undefined. Using Cre-directed optogenetics and in vivo neurophysiology in anesthetized mice of both sexes, here we studied whether TRPV1-lineage nociceptive and thermosensory fibers are primary neurons that drive trigeminal circuits reaching parabrachial taste cells. We monitored spiking activity in individual parabrachial neurons during photoexcitation of the terminals of TRPV1-lineage fibers that arrived at the dorsal spinal trigeminal nucleus pars caudalis, which relays orofacial somatosensory messages to the parabrachial area. Parabrachial neural responses to oral delivery of taste, chemesthetic, and thermal stimuli were also recorded. We found that optical excitation of TRPV1-lineage fibers frequently stimulated traditionally defined taste neurons in lateral parabrachial nuclei. The tuning of neurons across diverse tastes associated with their sensitivity to excitation of TRPV1-lineage fibers, which only sparingly engaged neurons oriented to preferred tastes like sucrose. Moreover, neurons that responded to photostimulation of TRPV1-lineage afferents showed strong responses to temperature including noxious heat, which predominantly excited parabrachial bitter taste cells. Multivariate analyses revealed the parabrachial confluence of TRPV1-lineage signals with taste captured sensory valence information shared across aversive gustatory, nociceptive, and thermal stimuli. Our results reveal that trigeminal fibers with defined roles in thermosensation and pain communicate with parabrachial taste neurons. This multisensory convergence supports dependencies between gustatory and somatosensory hedonic representations in the brain.

neuroscience↗