The effect of d-amphetamine on operant behaviour maintained under variable-interval schedules of reinforcement |
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Authors: | M J Morley C M Bradshaw E Szabadi |
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Institution: | (1) Department of Psychiatry, University of Manchester, Stopford Building, Oxford Road, M13 9PT Manchester, UK |
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Abstract: | Dose-response curves were obtained for the effects of d-amphetamine sulphate (0.1–3.2 mg/kg) on the operant performance of rats in variable-interval 4-min and variableinterval 20-min schedules of reinforcement. Response rates maintained under variable-interval 4-min were suppressed in a dose-dependent manner. Response rates maintained under variable-interval 20-min schedules tended to be elevated by low doses and suppressed by higher doses. The degree of response rate suppression was greater in the case of the variable-interval 4-min schedule. The results are consistent with the previously reported effect of d-amphetamine on the values of the two constants of Herrnstein's (1970) equation: the drug reduces the reinforcement frequency needed to maintain the half-maximum response rates (K
h) and lowers the maximum response rate (R
max) (Bradshaw et al. 1981 b). It is suggested that the effects of d-amphetamine on operant performance may involve two processes: an enhancement of motivation and a reduction of the capacity to respond. |
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Keywords: | d-Amphetamine Operant behaviour Variable-interval schedules Herrnstein's equation Rat |
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