Autoradiographic localization of thyrotropin-releasing hormone (TRH) receptors in human spinal cord

Thyrotropin-releasing hormone (TRH) exerts many effects upon spinal cord function in animals, and may also play a role in human spinal cord function. We have used the technique of quantitative autoradiography to anatomically localize specific receptors for TRH within human spinal cord. Highest concentrations of TRH receptors were localized within lamina II, the substantia gelatinosa. A moderate density of TRH receptors was found in lamina IX, the motor neurons of the anterior horn. Low levels of TRH receptors were noted throughout the remainder of the gray matter of the human spinal cord, and no TRH receptors were localized within white matter. This anatomic distribution of TRH receptors within the human spinal cord is consistent with the localization of endogenous TRH and the effects of exogenously applied TRH in animal studies. These results suggest that any effects of TRH on human spinal cord function may be mediated by TRH receptors.