Influence of response topography on the effect of apomorphine and amphetamine on operant behavior of pigeons

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Abstract
Key-pecking and treadle-pressing behavior were maintained in five pigeons by a mult. FI 5 key FI 5 treadle schedule of food presentation. Dose-effect curves for apomorphine and amphetamine on overall rates of responding in both FI components of the multiple schedule were determined. Effective doses of apomorphine caused dose-dependent decreases on treadle-pressing rates in all animals. Similarly, key pecking rates were decreased by increasing doses of apomorphine in two of the five pigeons. However, dose-dependent increases in key-pecking rates were caused by apomorphine in the other three birds. In this group of pigeons, the mean key-pecking rate was increased to over 500 % of the control rate by the dose of 1 mg/kg of apomorphine. Observation of the animals under the effect of apomorphine showed continuous pecking at the operative key in these three animals while the other two pecked at different places of the floor and walls of the experimental chamber. Appropriate doses of amphetamine caused rate-increasing effects on key-pecking as well as treadle-pressing rates of all pigeons. These results suggest that the increases in keypecking rate caused by apomorphine in some pigeons in a conventional operant situation are due to the orientation of the drug-induced stereotyped pecking toward the response-key, as a consequence of the topographic compatibility between this behavioral effect of apomorphine and the operant selected for study.