抄録
Orexins were initially reported as regulators of food intake. More recent reports suggest that they might play roles in the multiple functions of neuronal systems, causing medical conditions such as narcolepsy, a sleep disorder. Orexins and their receptors (OX1R and OX2R) are distributed in the brain regions involved in the autonomic and neuroendocrine control. Within the hypothalamus, orexins fibers and orexins receptors, especially OX2R, are found extensively in the paraventricular nucleus (PVN) of the hypothalamus. The PVN is an integrative center of the autonomic nervous system and neuroendocrine system. To examine the effects of orexin-A on the neural activity of the PVN neurons, we simultaneously recorded the single unit activities in the PVN, arterial blood pressure (ABP), and heart rate (HR) in conscious rats. Intracerebroventricular (i.c.v.) administration of orexin-A (0.3nmol) elicited increases in ABP and HR, as previously reported. Of irregularly active neurons (n=12), 6 neurons were excited, 2 neurons were inhibited, and 4 neurons were non-responsive. Majority of the neurons affected by orexin-A also responded to perturbation in ABP and systemic administration of cholecystokinin-8 (CCK). One phasically active neuron (putative vasopressin neuron) was excited by orexin-A. Thus orexin-A may modulate the neural activity of PVN neurons, which are involved in autonomic and neuroendocrine responses to intero-receptive stressors. [J Physiol Sci. 2007;57 Suppl:S237]
