Increased opioid receptor binding and G protein coupling in the accumbens and ventral tegmental area of postnatal day 2 rats
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Published on: November 6, 2018
Yanning Hou1, Mariana M Belcheva, Amy L Clark
1Department of Biochemistry & Molecular Biology, St. Louis University School of Medicine, MO 63104, USA.
Insights
In developing rat brains, mu opioid (MOP) and nociceptin/orphanin FQ (NOP) receptors show higher binding and G protein coupling in key areas like the nucleus accumbens and ventral tegmental area during the perinatal period compared to adults.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- Mu opioid (MOP) and nociceptin/orphanin FQ (NOP) receptor binding differs between perinatal and adult rats.
- The nucleus accumbens (Acb) and ventral tegmental area (VTA) are critical mesolimbic regions undergoing maturation.
Purpose of the Study:
- To investigate developmental changes in MOP and NOP receptor binding and G protein coupling in the rat mesolimbic system.
- To compare these receptor activities between postnatal day 2 (P2) pups and their dams.
Main Methods:
- Examined MOP and NOP receptor binding using specific radioligands.
- Assessed G protein coupling via GTPgammaS binding assays.
- Compared binding and coupling in the Acb and VTA of P2 pups and adult dams.
Main Results:
- P2 pups showed 2-fold greater MOP receptor binding in the Acb and NOP receptor binding in the VTA compared to dams.
- G protein coupling increases for both receptors in P2 pups exceeded binding differences.
- Female P2 pups exhibited greater MOP receptor G protein coupling in the Acb than males.
Conclusions:
- MOP and NOP receptors display enhanced binding and G protein coupling in specific mesolimbic regions of P2 rat pups.
- These developmental changes in the Acb and VTA may be significant for brain maturation.
- Sex differences in MOP receptor coupling were observed in the perinatal Acb.
Abstract:
In some regions of the developing rat brain such as the nucleus accumbens (Acb), mu opioid (MOP) receptor specific binding in the perinatal period exceeds that in the adult. To investigate the significance of these developmental changes, MOP and nociceptin/orphanin FQ (NOP) receptor binding and G protein coupling as determined by GTPgammaS binding experiments were examined in mesolimbic regions of postnatal day 2 (P2) pups and compared to those of their dams. Acb of the P2 pup exhibited 2-fold greater MOP receptor specific binding than that of the dam. In the ventral tegmental area (VTA), NOP specific binding was about 2-fold higher in the P2 pup. A correlation was found between MOP and NOP binding and their coupling to G protein on dam and P2 pup brain sections. However, the magnitude of increases in MOP and NOP receptor G protein coupling to G protein in P2 pups exceeded the 2-fold differences in binding between pups and dams. Furthermore, the amplitude of the MOP receptor G protein coupling in female P2 Acb was greater than increases in male P2 pup Acb. Differences in MOP and NOP binding and G protein coupling in other mesolimbic regions between P2 pups and dams were rarely observed. The data indicate that greater binding and G protein coupling of MOP and NOP receptors occur in discrete, mesolimbic regions of P2 pups when compared to their dams. It may be of significance that these brain regions, Acb and VTA, are undergoing maturation on P2.
