Topography and associations of leu-enkephalin and luteinizing hormone-releasing hormone neuronal systems in the human diencephalon.
Although several studies indicated that leu-enkephalin controls gonadal function, the morphological substrate of this modulation is unknown. To reveal potential interaction sites between leu-enkephalin and LH-releasing hormone (LHRH) in the hypothalamus, the distribution and connections of leu-enkephalin-immunoreactive (IR) and LHRH-IR systems were examined in the human diencephalon using double-label immunohistochemistry. First the leu-enkephalin-IR and LHRH-IR neural elements were mapped, then the maps of the two different neurotransmitter systems were superimposed unveiling the overlapping areas. The putative juxtapositions between leu-enkephalin-IR and LHRH-IR structures were revealed with double label immunocytochemistry. Close contacts were detected in the medial preoptic area and in the infundibulum/median eminence. In these areas, diaminobenzidine-silver-intensified, black leu-enkephalin-IR fibers abutted fusiform, brown, diaminobenzidine-labeled LHRH neurons often forming multiple contacts. Examination of semithin sections of these close associations with the aid of oil immersion revealed no cleft between the contacting LHRH-IR and leu-enkephalin-IR elements. Our findings indicate that the juxtapositions between LHRH-IR and leu enkephalin-IR neurons may be functional synapses forming the morphological substrate of the leu-enkephalin-modulated LHRH secretion in the human diencephalon. Moreover, the wide distribution of leu-enkephalin-IR elements suggests leu-enkephalin control of other diencephalic functions as well.
Dudás
Bertalan
B
Department of Pharmacology and Experimental Therapeutics, Loyola University Chicago, Strich School of Medicine, Maywood, Illinois 60153, USA. bdudas@lumc.edu
Merchenthaler
István
I
D000328:Adult; D000368:Aged; D001369:Axons / Q000737:chemistry; D002450:Cell Communication; D004027:Diencephalon / Q000166:cytology* / Q000378:metabolism; D004743:Enkephalin, Leucine / Q000032:analysis* / Q000502:physiology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis* / Q000378:metabolism; D006801:Humans; D007031:Hypothalamus / Q000737:chemistry; D007150:Immunohistochemistry; D008297:Male; D008473:Median Eminence / Q000166:cytology; D008875:Middle Aged; D009412:Nerve Fibers / Q000737:chemistry; D009474:Neurons / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D011301:Preoptic Area / Q000166:cytology; D013569:Synapses / Q000502:physiology
D007987:Gonadotropin-Releasing Hormone; D004743:Enkephalin, Leucine