PLC β4-independent Ca²+ rise via muscarinic receptors in the mouse suprachiasmatic nucleus

Cholinergic regulation of the suprachiasmatic nucleus (SCN) has been extensively studied although the intracellular signaling mechanisms are not well understood. We examined immunostaining for phospholipase C-β (PLC-β) families that couple to muscarinic acetylcholine receptors (mAChR) and demonstrated the expression of PLC-βI and β4 in the mouse SCN. Ca²⁺ imaging analysis indicated that the MI-mAChR antagonist, pirenzepine blocked carbachol-induced Ca²⁺ elevation in the SCN and the response was equivalent between the wild type and the PLC-β4-knockout mice. In addition, the knockout mice displayed locomotor and temperature rhythms coupling to 24 h light/dark cycles. Therefore, it was proposed that PLC-βI but not PLC-β4 was involved in the mAChR-mediated Ca²⁺ signaling in the SCN. (C) 2000 Lippincott Williams and Wilkins.