Daily and internal clock patterns of brain signaling molecules in night-active and day-active rodents

AVP mRNA exhibits a clear circadian rhythm, peaking by the end of the subjective day in both nocturnal mice and diurnal rodents.

• AVP mRNA shows a distinct daily pattern in the suprachiasmatic nuclei (SCN) of both Mus musculus and Arvicanthis ansorgei.
• In contrast to observations in rats, VIP and GRP mRNA levels in the SCN of mice and A. ansorgei are clock-controlled, but peak at different times.
• VIP and GRP mRNA peak during the middle of the subjective night in mice, which is 6 hours later than the peak of AVP mRNA.
• In A. ansorgei, VIP and GRP mRNA expression peaks almost simultaneously with AVP mRNA.
• In mice, exposure to light tends to increase mean levels of VIP and GRP peptide mRNA, differing from findings in rats.
• The distinct patterns of SCN neuropeptide mRNA profiles in both species may relate to their differences in activity patterns (diurnality vs. nocturnality).

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