VARIATION IN THE EXPRESSION OF THE MESSENGER-RNA FOR PROTEIN-KINASE-CISOFORMS IN THE RAT SUPRACHIASMATIC NUCLEI, CAUDATE-PUTAMEN AND CEREBRAL-CORTEX

Using in situ hybridization, we have examined mRNA expression for five isoforms of protein kinase C (PKC alpha, beta 1, beta 2, gamma and ep silon) in the rat suprachiasmatic nuclei (SCN) and other central sites during the 24 h cycle. The signal for each of these isoforms shows a marked local density within the SCN. In the absence of photic cues, th ere are changes in the expression of the mRNAs for the four isoforms t hat are Ca2+-dependent (alpha, beta 1, beta 2 and gamma), but not for one of the Ca2+-independent PKCs (epsilon). PKC alpha mRNA exhibits a monophasic rhythm of expression in the SCN with a peak at early subjec tive night, circadian time (CT) 14. In contrast, the mRNAs for PKC bet a 1, beta 2 and gamma show a biphasic rhythm in the SCN with peaks at early subjective day, CT 0, and early subjective night, CT 14. The fou r Ca2+-dependent isoforms may therefore subserve phase-related functio ns within the SCN at the onset of subjective night and, in the case of beta 1, beta 2 and gamma, also at the onset of subjective day. Variat ion in the mRNAs for PKC beta 1 and gamma (but not for alpha, beta 2 o r epsilon) is also found in the caudate putamen and in the cingulate a nd parietal cortex; the biphasic pattern of expression for these mRNAs is precisely in phase with that observed in the SCN. The beta 1 and g amma isoforms may therefore contribute to temporally regulated functio ns at sites outside the SCN. The present observations raise the possib ility that receptor-mediated regulation of circadian functions is modu lated or even gated by circadian changes in intracellular components t hat participate in distinct signal cascades. (C) 1998 Elsevier Science B.V.