Photoperiodic rhythm of cAMP concentration in the rat's preoptic region.

Photoperiodic influences on cAMP concentrations in the preoptic region and parietal cortex of the rat were studied at different ambient temperatures. In the preoptic region a photoperiodic rhythm is present at control Ta (22 degrees C) and is strongly attenuated at low Ta (-10 degrees C). In the parietal cortex no statistically significant photoperiodic changes were observed either at control or low T(a)s.