Effects of peripheral administration of rat urotensinII on circulation, and on distribution of c-Fos immunoreactive neurons in the brain

The purpose of this study was to examine the effects of intravenous injection of urotensinII on the systemic blood pressure and heart rate, and to examine whether the intraperitoneal administration of urotensinII evoked the stimulation of central neurons. Urotensin, originally isolated fish neuro-endocrine systems, is a peptide which consists of 12 amino acids. Lately human urotensinII was identified to be consisted from 11 amino acids. Receptors of urotensin have been found to highly distribute in the mammalian cadrdiovascular systems. It has been reported that urotensin evoked contraction of thoracic artery, while the dilatation of blood vessels was alternatively induced. In this study, we examined the effects of peripheral injection of rat urotensinII consisted of 14 amino acids on the circulation and on the activity of neurons in the brain. It was found that intravenous injection of rat urotensinII elicited dose-dependently decrease in blood pressure, and increase or decrease in heart rate. To examine whether an intraperitoneal injection of rat urotensinII induced an excitation of central neurons, we used immunohistochemical method to study the expression of c-Fos protein in neurons of the rat brain after intraperitoneal injection of rat urotensinII (test experiment). In the control experiment rat was intraperitoneally injected saline solution without rat urotensinII. It was found that intraperitoneal injection of rat urotensinII induced expression of c-Fos protein in several nuclei in the brain. These results suggested that rat urotensinII might exhibit physiological functions via central neuronal pathway as well as peripheral direct pathways