Period 2 gene deletion abolishes beta-endorphin neuronal response to ethanol.
BACKGROUND
Ethanol exposure during early life has been shown to permanently alter the circadian expression of clock regulatory genes and the beta-endorphin precursor proopiomelanocortin (POMC) gene in the hypothalamus. Ethanol also alters the stress- and immune-regulatory functions of beta-endorphin neurons in laboratory rodents. Our aim was to determine whether the circadian clock regulatory Per2 gene modulates the action of ethanol on beta-endorphin neurons in mice.


METHODS
Per2 mutant (mPer2(Brdml)) and wild type (C57BL/6J) mice were used to determine the effect of Per2 mutation on ethanol-regulated beta-endorphin neuronal activity during neonatal period using an in vitro mediobasal hypothalamic (MBH) cell culture model and an in vivo milk formula feeding animal model. The beta-endorphin neuronal activity following acute and chronic ethanol treatments was evaluated by measuring the peptide released from cultured cells or peptide levels in the MBH tissues, using enzyme-linked immunosorbent assay (ELISA).


RESULTS
Per2 mutant mice showed a higher basal level of beta-endorphin release from cultured MBH cells and a moderate increase in the peptide content in the MBH in comparison with control mice. However, unlike wild type mice, Per2 mutant mice showed no stimulatory or inhibitory beta-endorphin-secretory responses to acute and chronic ethanol challenges in vitro. Furthermore, Per2 mutant mice, but not wild type mice, failed to show the stimulatory and inhibitory responses of MBH beta-endorphin levels to acute and chronic ethanol challenges in vivo.


CONCLUSIONS
These results suggest for the first time that the Per2 gene may be critically involved in regulating beta-endorphin neuronal function. Furthermore, the data revealed an involvement of the Per2 gene in regulating beta-endorphin neuronal responses to ethanol.
Agapito
Maria
M
Endocrine Program, Department of Animal Sciences, Graduate Program of Neuroscience, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901, USA.
Mian
Nadia
N
Boyadjieva
Nadka I
NI
Sarkar
Dipak K
DK
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D017353:Gene Deletion; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D056950:Period Circadian Proteins / Q000235:genetics* / Q000502:physiology*; D001615:beta-Endorphin / Q000378:metabolism*
D056950:Period Circadian Proteins; D000431:Ethanol; D001615:beta-Endorphin