Campbell, U. C., Winsauer, P. J., Stevenson, M. W., & Moerschbaecher, J. M. (2004).
Effects of GABAA modulators on the repeated acquisition of response sequences in squirrel monkeys.
Journal of Experimental Analysis of Behavior,
82, 37-56.
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 GABAA modulator
triazolam (0.0032-0.1 mg/kg)
and the negative GABAA modulators ß-CCE (ethyl-ß-carboline-3-carboxylate;
0.01-1 mg/kg),
ß-CCM (methyl-ß-carboline-3-carboxylate; 0.0032-0.1 mg/kg), and FG-7142
(methyl-ß-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 GABAA 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 GABAA 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 GABAA modulators. Together, these data suggest that the effects
of both the positive and negative GABAA 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.
Key words: GABAA modulators, benzodiazepines, learning, repeated
acquisition, key press, squirrel monkeys