[35] Methods for investigating peptide precursors in the hypothalamus

In conclusion, as in the aminergic nervous system,7 the hypothalamic neuropeptides “turn over” at a rate sufficient to maintain a “steady state” concentration within the hypothalamus. However, unlike catecholamine-secreting neurons, the brain peptides are synthesized and secreted by a much more circuitous mechanism, involving ribosomal biosynthesis as larger prohormones, axonal transport to the site of secretion, and enzymic processing to the biologically active hormones. The methods described here, including in vitro incubation and high-performance size-exclusion and reverse-phase chromatography, have been found to be useful for examining and comparing the rate and mechanism of biosynthesis of several hypothalamic neuropeptides.