DISTRIBUTION OF TRH-POTENTIATING PEPTIDE (PS4) AND ITS RECEPTORS IN RAT-BRAIN AND PERIPHERAL-TISSUES

TRH-potentiating peptide (Ps4) is a peptide originally isolated from b ovine hypothalamus, which corresponds to the deduced rat prepro-TRH-(1 60-169) sequence. We have examined the distribution of Ps4 and [I-125- Tyr(0)]Ps4 binding sites in various rat tissues. Very high specific bi nding of [I-125-Tyr(0)]Ps4 was observed in pituitary membranes. Almost identical relative magnitude of binding was found in spinal cord, hyp othalamus, hippocampus and olfactory lobe. In addition, a high density of Ps4 binding sites was demonstrated in urogenital organs. The obser ved distribution pattern of Ps4 in brain tissues was similar to that r eported for TRH, with high concentrations in the hypothalamus and sign ificant amount in spinal cord and olfactory lobe. These findings suppo rt the hypothesis that the TRH-potentiating peptide could act as neuro modulator or neurotransmitter in the central nervous system (CNS). In peripheral tissues, very low concentrations of Ps4 were detected excep t in testis which seems to be the major locus for Ps4 biosynthesis. Th is study demonstrated for the first time that TRH-potentiating peptide and its receptors are widely distributed in the CNS and peripheral ti ssues. (C) Academic Press, Inc.