Brain diurnal levels of adenosine 3',5' cyclic monophosphate in C57 BL/6 and BALB/C mice.

Adenosine 3',5'-cyclic monophosphate (cAMP) was measured in whole brain of two inbred strains of mice (BALB/C and C57 BL/6) submitted to a lighting schedule consisting of 12 hr light (0700-1900) and 12 hr darkness (1900-0700). Different mean levels of cAMP were found in each strain. Furthermore, statistical analysis of diurnal brain cAMP fluctuations showed different nycthemeral rhythms in both strains. BALB/C was mainly characterized by the presence of very significant 0600 and 0800 harmonics and C57 BL/6 by an orthophase around 1700 hr. Because both strains were studied under the same experimental conditions of light, temperature and food availability, these factors cannot account for the observed differences, which were thus tentatively interpreted in terms of genetic regulatory processes.