The aim of this study was to determine if the psychostimulants, khat and amphetamine, exert similar effects in two tests of motor behaviors. Dose-response relationships were obtained for khat extract and D- and L-amphetamine given to mice by the intragastric route. Head twitch responses were significantly increased by khat and amphetamines. The latter were more potent than khat; dose-response curves for amphetamines had inverted U shapes. Khat extract decreased spontaneous motor activity, as measured by a photoactometer. Effects of amphetamines in this test were more variable and subject to dose dependent reversal. Other behaviors produced by higher doses of amphetamines interfered with specific motor responses under evaluation. Pretreatment with methysergide, a serotonin antagonist, significantly blocked head twitch responses but not spontaneous activity. Conversely, pretreatment with haloperidol decanoate, a dopamine receptor antagonist, prevented inhibition of spontaneous motor activity ordinarily evoked by khat and low dose D-amphetamine. We conclude that motor effects of khat and amphetamine resemble one another, but only at certain doses. Unlike khat, amphetamine causes additional behaviors that obscure motor responses of the types examined here. Results with transmitter receptor blockers suggest that motor effects of khat, like those of amphetamine, may be modulated by serotonin and dopamine. © 2002 Elsevier Science Ireland Ltd. All rights reserved.
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