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Repeated ethanol differently affects opioid peptide biosynthesis in the rat pituitary
B Przewłocka1, W Lasoń, R Przewłocki
1Neuropeptide Research Department, Institute of Pharmacology, Polish Academy of Sciences, Kraków, Mor.
Neuroendocrinology
|September 1, 1994
Summary
Ethanol affects proopiomelanocortin (POMC) and prodynorphin (PDYN) peptide levels in the rat pituitary gland, particularly during withdrawal. Chronic ethanol reduces POMC mRNA and beta-endorphin, while PDYN mRNA decreases with a rise in alpha-neoendorphin.
Area of Science:
- Neuroscience
- Endocrinology
- Pharmacology
Background:
- The pituitary gland synthesizes proopiomelanocortin (POMC) and prodynorphin (PDYN), precursors to various bioactive peptides.
- Ethanol consumption is known to impact neuroendocrine functions, but its specific effects on POMC and PDYN biosynthesis in the pituitary require detailed investigation.
Purpose of the Study:
- To investigate the influence of chronic and acute ethanol administration on POMC and PDYN biosynthesis in different lobes of the rat pituitary gland.
- To examine the effects of ethanol exposure and withdrawal on peptide levels and their corresponding messenger RNA (mRNA) in the pituitary and plasma.
Main Methods:
- In situ hybridization was employed to quantify POMC and PDYN mRNA levels in the anterior and intermediate lobes of the rat pituitary.
- Specific radioimmunoassays were utilized to measure beta-endorphin and alpha-neoendorphin peptide concentrations in pituitary tissue and plasma.
- Rats were subjected to a chronic intragastric ethanol administration regimen, followed by withdrawal periods, and also received acute ethanol doses.
Main Results:
- Chronic ethanol administration reduced POMC mRNA in the intermediate lobe and beta-endorphin levels in the neurointermediate lobe and plasma, especially during withdrawal.
- PDYN mRNA decreased in the anterior lobe during withdrawal, coinciding with an increase in alpha-neoendorphin levels.
- Acute ethanol administration decreased anterior lobe beta-endorphin and elevated plasma beta-endorphin, without affecting POMC or PDYN mRNA levels.
Conclusions:
- Ethanol significantly alters POMC and PDYN peptide and mRNA expression in a lobe-specific manner within the rat pituitary.
- Withdrawal from chronic ethanol exposure appears to be a critical period for observing significant changes in these neuroendocrine pathways.
- These findings highlight the complex interactions between ethanol and the pituitary's regulation of opioid peptide biosynthesis.