MSG effects on beta-endorphin and alpha-MSH in the hypothalamus and caudal medulla.
Monosodium glutamate (MSG) was given to neonatal male rats to determine its effects on neurons containing beta-endorphin (beta-END) and alpha-melanocyte stimulating hormone (alpha-MSH) within the basal hypothalamus (arcuate nucleus) and caudal medulla [nucleus tractus solitarius (NTS)] and on the levels of beta-END and alpha-MSH within these areas. Immunocytochemical studies demonstrated a reduction in the number of cells within the medial hypothalamic area (arcuate nucleus) among MSG-treated animals versus saline controls. MSG did not reduce the number of cell bodies within the caudal medulla (NTS). MSG significantly reduced beta-END and alpha-MSH immunoreactive levels in the basal hypothalamus as determined by radioimmunoassay. Whereas a significant reduction in the level of beta-END occurred in the ventral caudal medulla (VCM), none occurred in the dorsal caudal medulla (DCM). In contrast, levels of alpha-MSH increased significantly in the DCM among animals receiving MSG compared to control animals. This study documents the contribution of beta-endorphin containing neurons of the basal hypothalamus to areas of the caudal medulla. The effect of MSG on beta-endorphin and alpha-MSH neurons in these areas and their differential effects on levels in the caudal medulla areas raises questions about the sites of origin of these peptides.
Alessi
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NE
Department of Psychiatry, University of Michigan School of Medicine, Ann Arbor 48109.
Quinlan
P
P
Khachaturian
H
H
D000818:Animals; D001835:Body Weight / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology*; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008526:Medulla Oblongata / Q000187:drug effects / Q000378:metabolism*; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012970:Sodium Glutamate / Q000494:pharmacology*; D000521:alpha-MSH / Q000378:metabolism*; D001615:beta-Endorphin / Q000378:metabolism*
D005971:Glutamates; D000521:alpha-MSH; D001615:beta-Endorphin; D012970:Sodium Glutamate