Modification of behavioral and neurochemical effects of cocaine by haloperidol

Cocaine (20 mg/kg, i.p.) stimulated spontaneous motor activity (SMA) and induced stereotypy (ST) in rats. Haloperidol at 0.015 mg/kg, i.p. dose reduced or blocked cocaine-induced ST, but did not affect, drug-induced hyperactivity. At 0.03 mg/kg, i.p. dose of haloperidol, both behavioral effects were blocked. Cocaine decreased the norepinephrine (NE) and serotonin (5-HT) contents of diencephalon-midbrain (DM) and pons-medulla (PM) and increased dopamine (DA) contents in the DM and caudate nucleus (CN) at 20 min after its administration. Haloperidol (0.03 or 0.015 mg/kg) at 30 min postdrug produced opposite effects on the levels of NE, DA and 5-HT in the respective brain areas compared to cocaine. Given in combination, haloperidol reversed the effects of cocaine on the levels of NE, DA and 5-HT. Thus the cocaine-induced behavioral changes and their modification by haloperidol can be correlated to the neurochemical changes produced by these drugs alone or their combination.