Neuronal TRH synthesis: developmental and circadian TRH mRNA levels.

Peptide biosynthesis within a neuron involves several steps occurring at the soma and during its travel to the nerve terminal, where it accumulates to be released under stimulatory conditions. We have measured hypothalamic TRH and TRH mRNA during ontogeny and circadian cycle and observed that TRH mRNA variations are more prominent than TRH ones. On the basis of these results and in vitro release experiments, we propose a compensatory mechanism working at the nerve terminal which is activated after release.