Effects of gonadectomy and androgen supplementation on attention in male rats

Abstract

Androgens are hypothesized to enhance aspects of mnemonic processing. However, it is unclear whether the memory improvement is associated with changes in earlier aspects of information processing, such as attention. The present experiments examined the effects of gonadectomy or supplementation with testosterone or dihydrotestosterone on performance of male rats in a two-lever attention task that required discrimination of visual signals and non-signals. In Experiment 1, Long–Evans rats were trained in the attention task and then underwent gonadectomy or sham-surgery. Postsurgically, animals were tested for 20 sessions in the attention task and then received manipulations designed to increase attentional demands. Gonadectomized and sham-treated animals performed similarly during immediate postsurgical testing and across all manipulations. Finally, the effects of administering the muscarinic receptor antagonist scopolamine (0, 0.1, and 0.2 mg/kg) on attentional performance were assessed for all animals. Scopolamine decreased accuracy of signal detection but did not differentially affect gonadectomized and sham-treated animals. In Experiment 2, a new group of rats (not gonadectomized) was trained to perform the attention task and subsequently administered testosterone (0, 0.1, and 0.5 mg/kg) or dihydrotestosterone (0, 0.1, and 0.5 mg/kg) prior to performing the standard version of the attention task and in the presence of a visual distractor. Testosterone (0.5 mg/kg) decreased accuracy on non-signal trials and, at 0.1 mg/kg, decreased latencies to retrieve a reward. Dihydrotestosterone (0.5 mg/kg) decreased accuracy on non-signal trials during visual distractor sessions. The present data do not support the hypothesis that alterations in attention critically mediate androgen-induced changes in mnemonic processing. Supra-physiological androgen levels appear to be capable of impairing attentional processing.