EFFECTS OF CNS STIMULANTS ON THE INVIVO RELEASE OF THE COLOCALIZED TRANSMITTERS, DOPAMINE AND NEUROTENSIN, FROM RAT PREFRONTAL CORTEX

The effect of CNS stimulant drugs on the in vivo release of the colocalized neurotransmitters dopamine and neurotensin in rat prefrontal cortex was studied using microdialysis. Amphetamine, methylphenidate and nomifensine all increased extracellular fluid (ECF) levels of dopamine; however, their effects on neurotensin varied. Amphetamine increased both ECF dopamine (514 +/- 82% of basal) and neurotensin (350 +/- 49% of basal); however, the neurotensin increase lagged behind the increase in dopamine suggesting a possible trans-synaptic effect. Methylphenidate increased both dopamine and neurotensin (226 +/- 26% and 151 +/- 14% of basal respectively) co-synchronously. suggesting exocytosis of vesicles containing both dopamine and neurotensin. The nomifensine-induced increase in dopamine (202 +/- 23% of basal) was similar to that of methylphenidate, whereas the increase in neurotensin was significantly delayed and of lower magnitude (134 +/- 20% of basal). These data suggest that dopamine and neurotensin in part share a common releaseable pool in the prefrontal cortex. Moreover, dopamine may act presynaptically to increase neurotensin release and the different behavioral profiles of these psychostimulants may in part relate to their different effects on neurotensin release.