Thyrotropin-releasing hormone (TRH): apparent receptor binding in rat spinal cord.

Thyrotropin-releasing hormone (TRH) is unevenly distributed throughout the rat central nervous system including spinal cord, where exogenous TRH elicits profound pharmacological effects. [Pro-3H]TRH binds to 30,000 g pellet fraction from the spinal cord saturably, reversibly, and with high affinity (apparent Kd = 24-25 nM). This binding is displaced by TRH and related biologically active, but not inactive, peptides. TRH binding is evenly distributed throughout the rat spinal cord. Characteristics of this binding suggest an association with a physiologically relevant TRH receptor.