Degradation of thyrotrophin-releasing hormone in subcellular fractions from different areas of the rat central nervous system

Peptidases inactivating thyrotrophin-releasing hormone (TRH) were found to be present in two subcellular fractions prepared from the hypothalamus, thalamus, cortex and cerebellum of male rats, with the highest enzyme activity being detected in the cortex. TRH immunoreactivity was also measured in the two fractions from the 4 brain areas, after peptidase activity had first been removed by heat denaturation: the particulate fraction had a significantly higher TRH content than the supernatant fraction; of the regions investigated, the hypothalamus had the highest content, although TRH was detected in all the 4 brain regions. These findings provide further evidence that TRH may be one of several brain peptides having either a neuro transmitter function of a role as modulators of neuronal activity.