In vivo studies of the regulation of neuropeptide stores in structures of the rat brain.

In order to evaluate the regulation of neuropeptide stores in structures of the rat brain, the content of the specific messenger ribonucleic acid for the peptide precursor, of the precursor and of its biologically active peptide fragment, resulting from the precursor processing was measured. Enkephalin stores of the striatum, but not that of other structures, were upregulated by repeated daily doses of dopaminergic receptor antagonists of the D-1 type. Morphine tolerance failed to change stores of enkephalin in brain but produced a down-regulation of the synthesis of pro-opiomelanocortin in the hypothalamus. The regulation of diazepam binding inhibitor (DBI), the precursor of a family of putative endogenous ligands of the benzodiazepine recognition site, was studied during tolerance to benzodiazepines. Tolerance to diazepam increased the dynamic state of an octadecaneuropeptide (ODN), derived from DBI, in the cerebellum and cortex. The steady state or dynamic state of ODN were not changed in other structures of the brain of the rat, tolerant to diazepam.