抄録
Orexin A and B are a pair of neuropeptides which are implicated in the regulation of sleep-wakefulness and energy homeostasis. The regulatory mechanism of orexin neurons is poorly understood so far. In this study, we studied the effects of various neuropeptides on the activity of orexin neurons by calcium imaging using transgenic mice in which orexin neurons specifically express calcium sensing protein (Yellow Cameleon 2.1). We screened 21 neuropeptides and found that arginine-vasopressin (AVP), cholecystokinin-8s and oxytocin triggered a robust, concentration-dependent calcium increase in orexin neurons. We revealed the intracellular mechanisms and the subtype of AVP receptors involved in the AVP-induced activation of orexin neurons. The V1a AVP receptor antagonist, SR49059, inhibited AVP-induced activation of orexin neurons in a concentration-dependent manner, whereas the V1b and V2 receptor antagonists (SSR149415 and SR121463) had little effect. Removing extracellular calcium eliminated the AVP-induced increase in intracellular calcium concentration. These results suggested that the V1a receptor is involved in the AVP-induced activation of orexin neurons. This AVPergic excitatory input to orexin neurons might have an important role in the physiological regulation of sleep-wakefulness. [J Physiol Sci. 2006;56 Suppl:S156]
