ALTERATION IN THE LATERAL PARAGIGANTOCELLULAR NEURONAL ACTIVITY IN MORPHINE DEPENDENT RATS FOLLOWING ADOLESCENT OPIATE EXPOSURE

Background and Aim : Adolescence is considered as a critical developmental period during which long-lasting changes occur in the brain. Unfortunately, accumulating evidence support the growing non-medical use of morphine during adolescence. Although, this concern has remarkably been addressed during the recent years, cellular mechanisms underlying the long-term neurobiological and behavioral effects of opiate exposure during this stage are still remained largely unexplored. Lateral paragigantocellularis nucleus located in the rostral ventrolateral medulla, plays a pivotal role in the opiate tolerance and withdrawal syndrome. The present study examined the effect of adolescent morphine exposure on neuronal activity of lateral paragigantocellularis nucleus in adult morphine dependent rats.Methods : Adolescent male Wistar rats (30 days old) were administered increasing doses of morphine (from 2.5 to 25 mg/kg, s.c.) every 12 h, for 10 days. Control rats received saline with the same protocol. Thereafter, during adulthood (65 days old), they were rendered dependent on morphine. We used in vivo extracellular single-unit recording for investigating neural activity of LPGi in adult morphine treated rats following adolescent morphine exposure.Results : Results showed that adolescent morphine treatment significantly enhances the baseline activity of LPGi neurons in adult morphine dependent animals. It also changed the histogram pattern of inter spike intervals of LPGi neurons.Conclusion : It can be concluded that chronic morphine treatment during adolescence as a critical period of brain development causes prolonged neurobiological changes in the nervous system which lead to alteration of LPGi neuronal activity during adulthood and this may change the susceptibility to drug addiction.

Keywords:

Adolescence , Morphine , Extracellular single unit recording , LPGi nucleus