Progestins influence performance on cognitive tasks independent of changes in affective behavior

Abstract

In this study, the effects of progestins on various cognitive and affective tasks were investigated. Ovariectomized rats (N = 72) received subcutaneously 0.0, 4.0, or 8.0 mg/kg of progesterone (P), dihydroprogesterone (DHP), or 5α-pregnan-3α-ol-20-one (3α,5α-THP) suspended in 10% ethanol/sesame oil v/v. For the cognitive tasks (Y-maze, inhibitory avoidance, and object recognition), the subjects were injected after habituation and training trials and were tested 24 h later. For the nociception and affective tasks (open field, elevated plus-maze, and tailflick), the subjects were injected 1 or 24 h before testing. P reduced latencies to the goal arm in the Y-maze, enhanced latencies to the shock-associated side of the inhibitory avoidance chamber, and increased the percentage of time with a novel object. DHP reduced latencies to the goal arm, increased the percentage of correct choices in the Y-maze, and increased crossover latencies in the inhibitory avoidance task. 3α,5α-THP administration enhanced performance in the inhibitory avoidance task. P, DHP, and 3α,5α-THP increased the number of entries into the central squares of a brightly lit open field, open arm time in the elevated plus-maze, and tailflick latencies, when administered 1 h, but not 24 h, prior to testing. These data suggest that some progestins, when administered following habituation and training and 24 h prior to testing, produce changes in cognitive performance that do not coincide with overt changes in the affective behaviors examined.