Differential expression of protein kinase C βI (PKCβI) but not PKCα and PKCβII in the suprachiasmatic nucleus of selected house mouse lines, and the relationship to arginine-vasopressin

The functional significance of the suprachiasmatic nucleus (SCN) in circadian rhythm control of mammals has been well documented. The role of protein phosphorylation mediated by protein kinase C (PKC), however, is not well known. We report the immunocytochemical localization of three Ca²⁺-dependent PKC isoforms (α, βI, βII) within the SCN of selected house mouse lines that differ in behavioral circadian rhythm parameters. Optical density measurements revealed that the adult mice selected for low levels of nest-building behavior (small nest-builders) had more than threefold higher PKCβI immunostaining in the SCN than the mice selected for high levels of nest-building behavior (big nest-builders). A similar twofold difference between the adult small and big nest-builders was observed for the number of PKCβI-containing cells in the SCN. The non-selected control lines were intermediate. Ten-day-old pups revealed similar differences in PKCβI immunostaining in the SCN between the small and big nest-builders. PKCα and PKCβII immunostaining in the SCN was not different among the lines. PKCβI immunostaining was not different among the selected lines in the lateroanterior hypothalamic nucleus (LA) and the cornu ammonis field 1 (CA1) of the dorsal hippocampus and confirms the specificity of the difference in PKCβI immunostaining in the SCN among the selected lines. The significance of these findings is discussed in the context of differences among the lines in arginine-vasopressin (AVP) and light-induced Fos expression in the SCN, behavioral phase-delay responses to 15-min light pulses in constant darkness, and measures of the strength of the circadian activity rhythm expressed.