Expression of the cold thermoreceptor TRPM8 in rodent brain thermoregulatory circuits

• Published in: Journal of comparative neurology (1911) 2021-01, Vol.529 (1), p.234-256
• Main Authors: Ordás, Purificación, Hernández‐Ortego, Pablo, Vara, Hugo, Fernández‐Peña, Carlos, Reimúndez, Alfonso, Morenilla‐Palao, Cruz, Guadaño‐Ferraz, Ana, Gomis, Ana, Hoon, Mark, Viana, Félix, Señarís, Rosa
• Format: Article
• Language: English
• Subjects: Animals; Autonomic nervous system; Body Temperature Regulation - physiology; Brain - metabolism; Brain stem; Central nervous system; Cold Temperature - adverse effects; Female; Gene Expression; Hybridization; Hypothalamus; limbic system; Male; Menthol; Mice; Mice, Inbred C57BL; Nerve endings; Nerve Net - metabolism; Rats; Rats, Sprague-Dawley; Rats, Transgenic; reticular thalamus; rodents; RRID:AB_10989474; RRID:AB_141359; RRID:AB_2079751; RRID:AB_2340375; RRID:AB_2631173; RRID:AB_2721225; RRID:AB_300798; RRID:AB_477652; RRID:AB_514497; RRID:AB_514500; Sensory neurons; Septum; Thalamic reticular nucleus; Thalamus; Thermoregulation; Transient receptor potential proteins; TRPM Cation Channels - biosynthesis; TRPM Cation Channels - genetics; TRPM8
• ISSN: 0021-9967; 1096-9861
• DOI: 10.1002/cne.24694

The cold‐ and menthol‐activated ion channel transient receptor potential channel subfamily M member 8 (TRPM8) is the principal detector of environmental cold in mammalian sensory nerve endings. Although it is mainly expressed in a subpopulation of peripheral sensory neurons, it has also been identified in non‐neuronal tissues. Here, we show, by in situ hybridization (ISH) and by the analysis of transgenic reporter expression in two different reporter mouse strains, that TRPM8 is also expressed in the central nervous system. Although it is present at much lower levels than in peripheral sensory neurons, we found cells expressing TRPM8 in restricted areas of the brain, especially in the hypothalamus, septum, thalamic reticular nucleus, certain cortices and other limbic structures, as well as in some specific nuclei in the brainstem. Interestingly, positive fibers were also found traveling through the major limbic tracts, suggesting a role of TRPM8‐expressing central neurons in multiple aspects of thermal regulation, including autonomic and behavioral thermoregulation. Additional ISH experiments in rat brain demonstrated a conserved pattern of expression of this ion channel between rodent species. We confirmed the functional activity of this channel in the mouse brain using electrophysiological patch‐clamp recordings of septal neurons. These results open a new window in TRPM8 physiology, guiding further efforts to understand potential roles of this molecular sensor within the brain. The cold‐ and menthol‐activated ion channel transient receptor potential channel subfamily M member 8 (TRPM8) is the principal detector of environmental cold in mammalian sensory nerve endings. In this study, we show, by in situ hybridization and by the analysis of two different reporter mouse strains, that TRPM8 is also expressed in the rodent central nervous system. Our results open a new window to understand potential roles of this molecular sensor within the brain. In this cartoon, we illustrate the main places of expression of TRPM8. Magenta circles indicate positive cell bodies and green circles positive fibers.