The temperatures selected by white suckers, Catostomus commersoni, placed in a thermal gradient were significantly altered by intraperitoneal injections of cAMP (1 μg/g), cGMP (1 μg/g), caffeine (15 μg/g), and imidazole (5 μg/g). There was an endogenous, circadian, rhythm in the effects of cAMP, cGMP, and caffeine on temperatures selected by individual fish held under constant illumination. Depending on injection time, there was either a significant increase or decrease in temperatures selected by fish injected with cGMP or caffeine. The preferred temperatures selected were elevated by cAMP, though there was a rhythmic variation in the amplitude of the increase. Imidazole consistently decreased the preferred temperatures selected with no apparent rhythmic variation in its actions. These results are considered in relation to the roles of cAMP and cGMP in behavioural and physiological thermoregulation. © 1981.
Kavaliers, M. (1981). Circadian variations in the effects of cyclic nucleotides on the thermoregulatory behaviour of a teleost fish. Neuropharmacology, 20(3), 293–296. https://doi.org/10.1016/0028-3908(81)90136-2