Ahh, that warmth feels good.
We all know that many anoles species are very good at behaviorally regulating their body temperature by moving from an area that is too hot or too cold to another area that is just right. But how do they actually judge the thermal properties of a particular microsite? There’s been a lot of work on the sensation of temperature in mammals, but not so much in reptiles.
Recently, Erkin Kurganov and colleagues at the National Institutes of Natural Sciences, in Okazaki, Japan began to rectify this shortcoming, and their paper has just been published in Pflügers Archiv – European Journal of Physiology. Here’s the abstract:
Transient receptor potential ankyrin 1 (TRPA1) is a member of the large TRP super family of ion channels and functions as a Ca2+-permeable nonselective cation channel that is activated by various noxious stimuli. TRPA1 was initially identified as a potential mediator of noxious cold stimuli in mammalian nociceptive sensory neurons, while TRPA1s from nonmammalian vertebrates (snakes, green anole lizards, and frogs) were recently reported to be activated by heat, but not cold stimulus. In this study, we examined detailed properties of the green anole TRPA1 channel (gaTRPA1) related to thermal and chemical stimulation in whole-cell and single-channel recordings. Heat activates gaTRPA1 with a temperature threshold for activation of 35.8 °C, while heat together with allyl isothiocyanate (AITC), a chemical agonist, had synergistic effects on gaTRPA1 channel activation in that either the temperature threshold or activating AITC concentration was reduced in the presence of the other stimulus. Significant heat-evoked gaTRPA1 activation was observed in the presence but not absence of extracellular Ca2+. gaTRPA1 channels were also activated by heat and AITC in excised membrane patches with an inside-out configuration. By comparing the kinetics of heat- and AITC-evoked singlechannel currents, we defined similarities and differences of gaTRPA1 channel responses to heat and AITC. We observed similar current-voltage relationship and unitary amplitudes for heat- and AITC-evoked currents and found that heat-activated currents showed shorter durations of both open and closed times. Our results suggest that the gaTRPA1 channel is directly activated by heat and chemical stimuli.
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Anthony Geneva
I wonder if the activation threshold varies based on a species’ thermal environment. It would be cool to compare sequence and even expression of TRPA1 in a clade with lots of variation in thermal environment. Cybotoids come to mind as a good possibility.