Expression of mRNA for corticotropin-releasing hormone and vasopressin in the hypothalamus and amygdala of rats after administration of narcogenic

Abstract

Male Wistar rats received intraperitoneal injections of physiological saline (control), phenamine, fentanyl, ethanol, sodium ethaminal, or dexamethasone in increasing concentrations for 4 days. Forced administration of these drugs provided gradual load of the organism and prevented the development of tolerance. Such approach is extensively used for the development of drug addiction or several manifestations of this state. Expression of corticotropin-releasing hormone mRNA in the amygdala was maximum after administration of dexamethasone (0.46 arb. units vs. beta-actin), but was much lower in experiments with sodium ethaminal and fentanyl (0.07 and 0.037 arb. units, respectively). In the hypothalamus, enhanced mRNA expression was observed after injection of sodium ethaminal, ethanol, and fentanyl (0.8, 0.37, and 0.039 arb. units, respectively). Phenamine did not increase mRNA expression in the amygdala and hypothalamus. Expression of vasopressin mRNA was not detectable in brain structures of animals from various groups. Our results indicate that the hypothalamic reinforcement system provides a similar response to narcogens, whereas the extended amygdala includes elements of both reinforcement and stress reactivity.