Time-dependent results of amino acid uptake studies of learning in frogs

Myelencephalic grass frogs were trained to elevate the right forelimb to avoid a shock plate at several times in relation to administration of 3H-leucine and sacrifice. Total radioactivity (excluding 3H2O) and radioactivity in the soluble pool were significantly greater in the trained animals. The differences between trained and yoked animals decreased with increasing time, up to 30 min after training. The opposite trend was apparent in TCA insoluble material; differences between trained and yoked animals increased with increasing time after training. Similar experiments with 3H-inulin provide evidence that the effects were not due to generalized permeability increases or circulatory alterations.