EFFECTS OF COCAINE AND d‐AMPHETAMINE ON THE REPEATED ACQUISITION AND PERFORMANCE OF CONDITIONAL DISCRIMINATIONS¹

Abstract

The acute and chronic effects of cocaine and d-amphetamine on food-reinforced behavior were investigated in pigeons responding on a two-component multiple schedule. In one component, the behavioral task consisted of the same chain of conditional discriminations each session (performance). In the other component, the chain of conditional discriminations was changed from session to session (learning). In comparison to control sessions, both acute cocaine and d-amphetamine increased errors in each component of the multiple schedule. Responding in the learning component, however, was generally disrupted at lower doses than those that affected responding in the performance component. At high doses, both drugs produced pauses in responding in each component in three of the four subjects. Pausing engendered by d-amphetamine was approximately twice as long as that under cocaine. Upon chronic administration, both the pausing and error-increasing effects of each drug diminished. Drug-induced changes in timeout responding, however, did not decrease during chronic administration. Redeterminations of the d-amphetamine dose-effect curves following chronic cocaine administration suggested the existence of cross-tolerance between cocaine and d-amphetamine. Both the acute and chronic data are consistent with the view that conditions of stimulus control may modulate the behavioral effects of drugs.

AN EXPERIMENTAL ANALYSIS OF THE EFFECTS OF d‐AMPHETAMINE AND COCAINE ON THE ACQUISITION AND PERFORMANCE OF RESPONSE CHAINS IN MONKEYS

“…As the dose of each drug was increased, the overall response rate decreased, the overall accuracy was impaired (i.e., percent errors increased), and there was less within-session error reduction (acquisition). Similar disruptive drug effects were obtained in the Moerschbaecher et al (1979) study, where pigeons acquired a different chain of conditional discriminations each session. In that study, the repeated-acquisition procedure constituted one component of a multiple schedule. In the other component, the chain of conThis research was supported in part by Public Health Service Grants DA 01528 and DA 05014.…”

“…Although the differential drug effects on learning and performance can be interpreted in terms of stimulus control, there is reason to believe that the baseline rate of reinforcement was an important determinant (Moerschbaecher et al, 1979). Components of a multiple schedule with different rates of reinforcement have been shown to be differentially sensitive to nonpharmacological variables.…”

“…The disruptive effects of both drugs on behavior in the learning component were attenuated when the drugs were administered during the session after the response chain had been acquired. It was concluded that the greater sensitivity of the learning component to disruptive drug effects is related to the relatively weak stimulus control and/or the lower rate of reinforcement associated with that component.Key words: repeated acquisition, multiple schedule, response chains, d-amphetamine, cocaine, prefeeding, stimulus control, key press, monkeysPrevious research has shown that repeatedacquisition baselines are sensitive to the effects of d-amphetamine and cocaine in rats (Schrot, Boren, Moerschbaecher, & Simoes Fontes, 1978) and pigeons (Moerschbaecher, Boren, Schrot, & Simoes Fontes, 1979;Thompson, 1973Thompson, , 1977Thompson, , 1978. In Thompson's experiments, pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors.…”

“…Previous research has shown that repeatedacquisition baselines are sensitive to the effects of d-amphetamine and cocaine in rats (Schrot, Boren, Moerschbaecher, & Simoes Fontes, 1978) and pigeons (Moerschbaecher, Boren, Schrot, & Simoes Fontes, 1979;Thompson, 1973Thompson, , 1977Thompson, , 1978. In Thompson's experiments, pigeons acquired a different four-response chain each session by responding sequentially on three keys in the presence of four colors.…”

Perinatal Methanol Exposure in the Rat II Behavioral Effects in Neonates and Adults

“…It seems likely that the difficulty of the task may have played a critical role in revealing the neurotoxic effects of methanol. Other studies have shown that as task difficulty increases due to weak stimulus control of behavior (e.g., Laties, 1975) and/or increased complexity in response sequences (e.g., Polidora, 1963;Thompson, 1975;Moerschbaecher et al, 1979), sensitivity increases to disruption by other variables including environmental toxicants and drugs. That methanol effects were statistically significant only for the asymptote of Matrix 2 indicates the ease with which neurotoxic effects might be overlooked with less-complex behavioral tasks.…”