TRH in the rat cerebellum: I. Distribution and concentration.

We determined the regional distribution and concentration of endogenous TRH in the rat cerebellum. Radioimmunoassay of endogenous TRH extracted and purified from five different regions of the rat cerebellum and whole hypothalamus showed that the cerebellar vermis contained 24 pg/mg, the hemispheres 74 pg/mg, the deep cerebellar nuclei 148 pg/mg, and the flocculo-nodular region 559 pg/mg of TRH. The highest concentration of TRH was in the cerebellar paraflocculi, which contained 786 pg/mg. The hypothalamic concentration of TRH was 465 pg/mg. Assay of the non-purified tissue fractions (crude extracts) resulted in lower TRH values in accordance with data previously reported by other authors. Bioassay analysis of TRH in purified fractions resulted in values similar to those obtained by radioimmunoassay. On the basis of these findings we hypothesize a functional role for TRH in the cerebellum.