Inhibition by DN-1417 (a TRH derivative) of [3H]GABA binding in the rat brain.

The administration of DN-1417, a synthetic derivative of TRH with more potent central action, significantly reduced specific [3H]GABA binding in the cerebellum, whereas [3H]GABA binding in the cerebral cortex was not changed. Scatchard analysis showed that the decreased [3H]GABA binding in the cerebellum was due to decreased binding sites of both high and low affinities. [3H]GABA binding to brain synaptic membranes was not affected by the addition of either TRH or DN-1417 in vitro. These findings suggest that TRH may play a role in regulating GABA receptors in the rat cerebellum.