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Effect of a single administration of a dose (5, 10, or 15 mg/kg, i.p.) of cocaine hydrochloride on spontaneous motor activity (SMA) and stereotypy (ST), and interactions between these behaviors were investigated in rats. SMA showed peak increases within 10 min and at 120 min after cocaine injection. Drug-induced stereotypy was maximal during the interval between these two peaks in SMA. Several neurotransmitters may be involved in the interactions between SMA and ST.

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In an attempt to correlate the behavioral and neurochemical effects of d-and I-amphetamines, the time courses of the effects of the two isomers (1 mg/kg; base, i.p.) were studied on spontaneous motor activity (SMA) and stereotyped behavior (ST) as well as on the concentrations of norepinephrine (NE), dopamine (DA), and serotonin (5-HT) in discrete brain areas, such as the caudate nucleus (CN), pons-medulla (PM), and diencephalonmidbrain (DM) in rats. In addition, the dose-response relationship for d-isomer (0.5-2 mg/ kg, i.p.) and I-isomer (1-4 mg/kg, i.p.) was also studied on SMA and ST. SMA increased with the dose up to 1.5 mg/kg for d-isomer and up to 3 mg/kg for I-isomer and then decreased, whereas ST increased with the dose for both the isomers. At 1 mg/kg dose, SMA reached its peak during the fourth postdrug 20-minute period for both d-and I-isomers, whereas ST reached its peak during third to fifth 20-minute periods for d-isomer and during the third period for the I-isomer. The d-isomer significantly increased the DA levels in the CN and DM at 30 minutes postdrug, which reached their maximum at 60 minutes, whereas NE levels in the PM had no significant change at 30 minutes, but were significantly reduced in the DM at 30 minutes and in both PM and DM at 60 minutes postdrug; 5-HT levels in the PM and DM showed no significant change. Compared to d-amphetamine, the I-isomer at 30 and 60 minutes postdrug caused more or less similar changes in the NE levels in the DM and PM, whereas it produced less increase in the DA levels in the CN and DM and significant decrease in 5-HT levels in the DM and PM. It appears that the difference in the behavioral effects induced by the two isomers of amphetamine may be due to the difference in their effects on dopaminergic and serotonergic systems.