preproenkephalin and chlornaltrexamine

The irreversible opiate antagonists beta-funaltrexamine (beta-FNA) and beta-chlornaltrexamine (beta-CNA) were injected into rat striatum. One day later, mu-opioid receptor binding, as assessed by receptor autoradiography, was abolished in the injected striatum, while [3H]spiperone binding remained largely unaffected. In situ hybridization was used to examine possible effects on striatal proenkephalin mRNA and prodynorphin mRNA content. The levels of proenkephalin mRNA were increased ipsilaterally following beta-CNA injection, but were slightly decreased following beta-FNA injection. Prodynorphin mRNA content was also increased by beta-CNA administration. The results provide evidence for a differential modulation of striatal opioid peptide gene expression via distinct opioid receptors.

Topics: Animals; Corpus Striatum; Enkephalins; Gene Expression Regulation; Male; Naltrexone; Protein Precursors; Rats; Rats, Inbred Strains; Receptors, Opioid; RNA, Messenger