In addition to its use for heroin addiction pharmacotherapy in general, buprenorphine has advantages in treating maternal heroin abuse. To examine the gestational effects of buprenorphine on opioid receptor signaling, the [ 35S]-GTPγS in situ binding induced by the μ agonist [D-Ala2,MePhe4,Gly5-ol] enkephalin (DAMGO) or the nociceptin/orphanin FQ (N/OFQ) agonist was measured in mesolimbic structures of pup brains from pregnant rats administered with buprenorphine± naloxone, naloxone, or methadone by osmotic minipump. Drug- and gender-based changes in DAMGO- and N/OFQ-induced GTPγS binding were discovered in mesolimbic regions of dam, P2, and P7 brains. Buprenorphine and/or methadone gestational treatment attenuated DAMGO-induced GTPγS binding in some dam and male P2 mesolimbic regions. Methadone diminished DAMGO-induced GTPγS binding in almost all monitored brain regions of the dam but had few effects on their N/OFQ-induced GTPγS binding. Naloxone used in combination with buprenorphine blocked the inhibition by buprenorphine alone on DAMGO-induced GTPγS binding. In contrast to its inhibitory effects on DAMGO-induced GTPγS binding, buprenorphine stimulated N/OFQ-induced GTPγS binding in male P2 nucleus accumbens and lateral septum. Brain region-dependent gender differences in DAMGO-induced GTPγS binding were seen in P2 pups, and males showed greater sensitivity to buprenorphine and methadone than females. Our findings on μ opioid receptor (MOR) GTP-binding regulatory protein (G protein) coupling and its gender dependency are consistent with our earlier studies on μ receptor binding adaptation induced by buprenorphine in dams and neonatal rats after in utero treatment regimens, and they extend the gestational effects of this opiate to μ and N/OFQ receptor functionality.
- G protein
- Neurotransmitters, modulators, transporters, and receptors
- Opioid receptor
- Opioid receptors
- [D-Ala,MePhe,Gly-ol] enkephalin