Vasoactive intestinal peptide and corticotropin-releasing hormone increase beta-endorphin release and proopiomelanocortin messenger RNA levels in primary cultures of hypothalamic cells: effects of acute and chronic ethanol treatment.
BACKGROUND
beta-Endorphin (beta-EP) neurons are involved in ethanol's action on a variety of brain functions, including positive reinforcement. These neurons are innervated by vasoactive intestinal peptide (VIP)-containing and corticotropin-releasing hormone (CRH)-containing neurons in the hypothalamus. Whether these neuropeptides affect beta-EP neuronal function in the presence or absence of ethanol has not previously been determined.


METHODS
The authors determined the effects of VIP and CRH on gene expression and peptide release from beta-EP neurons in primary cultures of mediobasal hypothalamic cells. The effects of receptor antagonists on VIP- and CRH-induced beta-EP release was determined. Furthermore, the authors studied the effects of acute and chronic treatment with ethanol on the response of beta-EP neurons to VIP and CRH. Real-time reverse-transcription polymerase chain reaction was used for messenger RNA (mRNA) detection, and radioimmunoassay was used for hormone measurements.


RESULTS
We show that beta-EP neurons responded concentration dependently to VIP and CRH treatments by increasing both beta-EP release and proopiomelanocortin mRNA expression. Simultaneous treatment with a nonspecific receptor antagonist reduced the ability of CRH or VIP to induce beta-EP release from mediobasal hypothalamic cells. Acute treatment with ethanol increased beta-EP neuronal gene expression and the secretory response to CRH and VIP. However, previous exposure to chronic ethanol reduced the CRH and VIP responses of these neurons.


CONCLUSIONS
These results indicate that VIP and CRH stimulate beta-EP release from hypothalamic cells in primary cultures and that the stimulatory and adaptive responses of beta-EP neurons to ethanol may involve alteration in the responsiveness of beta-EP-secreting neurons to CRH and VIP.
Poplawski
Michael M
MM
Endocrinology Program, Center of Alcohol Studies and Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901-8525, USA.
Boyadjieva
Nadka
N
Sarkar
Dipak K
DK
D000818:Animals; D002478:Cells, Cultured; D002492:Central Nervous System Depressants / Q000494:pharmacology*; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D000431:Ethanol / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D011247:Pregnancy; D011333:Pro-Opiomelanocortin / Q000096:biosynthesis* / Q000378:metabolism; D012313:RNA / Q000096:biosynthesis / Q000302:isolation & purification; D012333:RNA, Messenger / Q000096:biosynthesis*; D011863:Radioimmunoassay; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014660:Vasoactive Intestinal Peptide / Q000008:administration & dosage / Q000494:pharmacology*; D001615:beta-Endorphin / Q000378:metabolism*
D002492:Central Nervous System Depressants; D012333:RNA, Messenger; D014660:Vasoactive Intestinal Peptide; D000431:Ethanol; D001615:beta-Endorphin; D012313:RNA; D011333:Pro-Opiomelanocortin; D003346:Corticotropin-Releasing Hormone