Age-dependent muscarinic stimulation of beta-endorphin secretion from rat neurointermediate lobe in vitro.
The effect of acetylcholine on the neurointermediate lobe beta-endorphin secretion was studied in the neonatal and in the adult rat in vitro. Acetylcholine stimulated beta-endorphin secretion from the 2-day- and 5-day-old neurointermediate lobe, the effect was dose dependent and more pronounced in the presence of the cholinesterase inhibitor eserine. The 10-day-, the 21-day-old and the adult rat neurointermediate lobes did not respond to acetylcholine, even in the presence of eserine. Basal beta-endorphin secretion was elevated by the D2 receptor antagonist sulpiride, but acetylcholine was without effect in the 10-day-old and in the adult neurointermediate lobe even after dopamine receptor blockade. The beta-endorphin stimulatory response to acetylcholine was diminished by the M1 muscarinic receptor antagonist pirenzepine and blocked by the M3 > M1 antagonist 4-diamino-phenyl-piperidine (4-DAMP). The selective M2 antagonist methoctramine and nicotine had no effect. These data indicate that the neurointermediate lobe beta-endorphin secretion is under special muscarinic cholinergic regulation for a relatively short time after birth. The disappearance of this stimulatory cholinergic effect in later life might be due to changes in the intracellular secretory machinery in the IL and/or to the uncoupling of the cholinergic receptors from the intracellular signal transduction system(s) responsible for the stimulated secretion in the rat melanotrope cells.
Acs
Z
Z
Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest.
Barna
I
I
Koenig
J I
JI
Makara
G B
GB
D000109:Acetylcholine / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000375:Aging / Q000378:metabolism*; D000818:Animals; D000831:Animals, Newborn; D005260:Female; D066298:In Vitro Techniques; D008297:Male; D018721:Muscarinic Agonists / Q000494:pharmacology*; D018727:Muscarinic Antagonists / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D001615:beta-Endorphin / Q000378:metabolism*
D018721:Muscarinic Agonists; D018727:Muscarinic Antagonists; D001615:beta-Endorphin; D010830:Physostigmine; D000109:Acetylcholine