Identification of neurons expressing thyrotropin releasing-hormone receptor mRNA in spinal cord and lower brainstem of rat

The distribution of mRNA coding for a pituitary thyrotropin releasing-hormone (TRH) receptor was examined on sections of spinal cord and lower brainstem of rat using in situ hybridization. Hybridization signals were observed over large neurons in the ventral horn in cervical, thoracic, and lumbar segments of spinal cord, and over neurons in the motor nuclei of the lower brainstem. Although significant thyrotropin-releasing hormone binding has been reported in the superficial dorsal horn, only background levels of hybridization were observed over neurons in this region. These findings suggest that mRNA coding for thyrotropin-releasing hormone receptor is expressed in some spinal and brainstem motor neurons. Since many of these neurons are innervated by TRH-containing afferents, TRH may exert a direct effect upon at least some of these cells.