Quantitative autoradiography of TRH receptors in discrete brain regions of different mammalian species.

The results clearly show marked heterogeneity and ubiquity of the CNS distribution of TRH receptors across several mammalian species including man. The use of high resolution autoradiography coupled with image analysis has permitted the visualization and quantification of TRH receptor density in even very small regions and nuclei of the CNS. This technique will undoubtedly help elucidate the other areas of TRH receptor localization that have thus far escaped detection in mammals and that are yet to be studied in lower vertebrates. Although an attempt has been made to correlate the presence of the peptide, its receptors, and its possible physiological functions, only further detailed physiological/behavioral investigations will ultimately unravel and support the diverse neurotransmitter and trophic roles of TRH in CNS and endocrine function.