The regional distribution of thyrotropin releasing hormone, leu-enkephalin, met-enkephalin, substance P, somatostatin and cholecystokinin in the rat brain and pituitary.

There was no apparent difference in the regional distribution of neuropeptides in the brain of male and female rats. The highest levels of immunoreactive leu-enkephalin, TRH, substance P and somatostatin were found in the hypothalamus, while the striatum and the cerebral cortex had the highest concentrations of met-enkephalin and cholecystokinin respectively. The lowest concentrations of these were found in the cerebellum. Enkephalins (cerebral cortex), substance P (cerebral cortex and brain stem), and somatostatin (brain stem and striatum) showed higher level in the female while enkephalin and substance P contents in the anterior pituitary were higher in the male.