DEVELOPMENTAL DIFFERENCES IN ACUTE NIGROSTRIATAL AND MESOCORTICOLIMBIC SYSTEM RESPONSE TO HALOPERIDOL

Dose-dependent effects of haloperidol (2.66 nmol/kg to 79.8 mmol/kg, I P) on levels of dopamine, homovanillic acid (HVA) and dihydroxyphenyla cetic acid (DOPAC) were assessed in the corpus striatum, nucleus accum bens, and medial prefrontal cortex (PFCTX) of 18-, 30-, and 110-day-ol d rats. Eighteen-day-old rats were 35% and 63% more sensitive than adu lts to the effects of haloperidol on striatal and accumbens turnover a nd had steeper dose-response curves. The dose-response function in the PFCTX was similar to striatum at 18 days, but became shallower and no nsigmoidal with age. Maximally effective doses of haloperidol produced , at all ages, a comparable percent rise in DOPAC levels in all region s. With maturation, the percent rise in HVA progressively outstripped DOPAC response in nucleus accumbens and striatum. Overall, prominent d evelopmental differences emerged in these regions in their sensitivity and response to haloperidol, which are consistent with previously rep orted differences in behavioral sensitivity.