Injection of neuropeptide Y (NPY, 0.01-1.0 nmol in 0.25 μl vehicle) into the supraoptic nucleus of unanesthetized rats increased plasma vasopressin, measured by radioimmunoassay, to a maximum of 90±18 ng/liter. Injections of vehicle or somatostatin did not increase plasma vasopressin, nor did injections of NPY into the amygdala. Double-labelling immunohistochemical studies demonstrated that fibers containing NPY-like immunoreactivity form a close association with vasopressin immunoreactive perikarya in the supraoptic nucleus. It appears that NPY may directly excite vasopressin-containing neurons causing secretion of vasopressin.
- Neuropeptide Y
- Supraoptic nucleus