Effects of GABA sub(A) modulators on the repeated acquisition of response sequences in squirrel monkeys

• Published in: Journal of the experimental analysis of behavior 2004-07, Vol.82 (1), p.37-56
• Main Authors: Campbell, U C, Winsauer, P J, Stevenson, M W, Moerschbaecher, J M
• Format: Article
• Language: English
• Subjects: Saimiri
• ISSN: 0022-5002

The present study investigated the effects of positive and negative GABAA modulators under three different baselines of repeated acquisition in squirrel monkeys in which the monkeys acquired a three-response sequence on three keys under a second-order fixed-ratio (FR) schedule of food reinforcement. In two of these baselines, the second-order FR schedule and the discriminative stimuli for the response sequence were manipulated ("chain-strained" and "tandem-strained"). In the third baseline condition, response-independent tail shock was presented during acquisition of the response sequence. All of these baselines maintained high error levels and produced slow rates of acquisition. Under both the chain-strained and tandem-strained conditions, the positive GABA sub(A) modulator triazolam (0.0032-0.1 mg/kg) and the negative GABA sub(A) modulators beta -CCE (ethyl- beta -carboline-3-carboxylate; 0.01-1 mg/kg), beta -CCM (methyl- beta -carboline-3-carboxylate; 0.0032-0.1 mg/kg), and FG-7142 (methyl- beta -carboline-3-carboxamide; 0.18-10 mg/kg) dose-dependently decreased overall response rate compared to administration of saline (control). Under the same two conditions, triazolam and the negative GABA sub(A) modulators also increased the percentage of errors; however, the effects on accuracy frequently depended on the baseline condition and the particular modulator. In contrast, triazolam only decreased errors and enhanced acquisition in the presence of concurrent response-independent tail shock when compared to saline administration under this condition. The neutral GABA sub(A) modulator, flumazenil (1 mg/kg), had no effect on rate or accuracy of responding when administered alone, but antagonized the rate-decreasing and error-increasing effects produced by the negative GABA sub(A) modulators. Together, these data suggest that the effects of both the positive and negative GABA sub(A) modulators on acquisition can be similar in squirrel monkeys (i.e., both types of modulator may produce rate-decreasing and error-increasing effects) and that their effects on acquisition depend, in part, on the environmental conditions maintaining acquisition.