Correlation between pentobarbital suppressed cerebellar cyclic GMP and performance of a swimming task.

Ovariectomized female Sprague-Dawley rats were trained to swim a 2.5 m course. On the day of the experiment the time required for each animal to swim the course was determined, and then the animal received either saline or one of 4 dosages of sodium pentobarbital, intravenously. Four minutes after treatment the animal's swim time was again recorded, and the animal was immediately killed by microwave irradiation. The cerebellum was collected for subsequent determination of cyclic guanosine monophosphate (cGMP). Pentobarbital caused a dosage-dependent suppression of cerebellar cGMP which was highly correlated with a drug-induced increase in the time required to swim 2.5 m. These data provide the first evidence of a correlation between a barbiturate-induced effect on a neurochemical parameter and impaired performance of a learned behavior.