The neurosteroid pregnenolone sulfate reduces learning deficits induced by scopolamine and has promnestic effects in mice performing an appetitive learning task

The effects of the neurosteroid pregnenolone sulfate (PS) on learning as well as on scopolamine-induced learning deficits were studied in Swiss mice using an appetitively reinforced Go-No Go visual discrimination task. Subcutaneous (SC) administration of scopolamine (0.3-3 mg/kg) after the first session of training dose-dependently impairs learning during the following sessions in this task. Moreover, intracerebroventricular (ICV) administration of PS (0.01-10 nmol) dose-dependently blocks learning deficits induced by scopolamine (3 mg/kg), with the most potent effects at the dose of 0.5 nmol PS. In addition to antagonizing the amnestic effects of scopolamine, PS (0.5 nmol ICV) has a memory-enhancing effect, when administered alone after the first training session. Scopolamine (3 mg/kg SC) also produced substantial deficits on retrieval performance in the Go-No Go visual discrimination task, and caused motor disturbances, when administered 15 min before testing. PS (0.5 nmol ICV) also reduced scopolamine-induced deficits on retrieval but had no effect on scopolamine-induced motor impairments in the traction reflex test. Such a rapid effect of PS on memory processes may be mediated via NMDA and/or GABA(A) receptors.