抄録
We have examined the effects of peripheral administration of cannabinoids in the paraventricular (PVN) and the supraoptic nuclei (SON) of rats. Intraperitoneal (Ip) administration of CP 55,940 (CB1 and 2 agonist), anandamide (CB1 and 2 agonist) and noladin ether (selective CB1 agonist) caused a marked induction of the c-fos gene expression in the PVN and the SON. These effects were dose-dependent. Plasma corticosterone and oxytocin levels were significantly increased by ip administration of cannabinoids, but arginine vasopressin level was not changed. Furthermore, to determine the process of modulating activities of the SON neurons via CB-1 receptors, we have investigated the effects of CP 55,940 on excitatory and inhibitory synaptic transmission in the rat SON. Whole-cell patch clamp recordings were performed from magnocellular neurons in the SON in in vitro brain slice preparation. CP 55,940 significantly reduced both excitatory and inhibitory postsynaptic currents, and these changes were potently reversed by subsequent application of AM 251 (CB1 antagonist). These results suggest that cannabinoids may be involved in the regulation of the neuronal activity in the PVN and the SON, and at least in the SON, modulate the activity of the neurosecretory cells via presynaptic inhibition of excitatory and inhibitory synaptic transmission. [Jpn J Physiol 55 Suppl:S147 (2005)]
