Potency of the N3im-methyl analog of TRH in the induction of shaking movements in the rat.

The relative potencies of TRH analogs in provoking a shaking response in rats were determined. Bilateral administration of 0.011-2.0 mug TRH analog into the periaqueductal-fourth ventricular spaces of the barbiturate-anesthetized rat showed that N3im-methyl TRH was approximately 10X more potent than TRH, whereas N1im-methyl TRH was approximately 10X less potent than TRH. These results indicate that the potencies of the TRH analogs in inducing shaking parallel their thyrotropin-releasing activities.