Dynorphin (1-8) inhibits stimulated release of oxytocin but not vasopressin from isolated neurosecretory endings of the rat neurohypophysis.
The effects of the opioid peptide dynorphin (1-8) on oxytocin and vasopressin release at the level of isolated neurosecretory endings were investigated. Neurosecretory endings prepared by homogenization and centrifugation were placed on a filter and constantly superfused. Stimulated hormone release was evoked by potassium depolarization (30 mM) and simultaneous increase of the osmolarity (20 mosmol/1). Stimulation resulted in two peaks of hormone release--a short first peak and a longer second one. Addition of dynorphin (1-8) (10(-7) M) to the superfusion buffer significantly diminished the first peak of oxytocin release and totally abolished the second. There was no effect of dynorphin (1-8) on vasopressin release.
D000818:Animals; D004399:Dynorphins / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009490:Neurosecretory Systems / Q000187:drug effects; D010121:Oxytocin / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology*; D010904:Pituitary Gland, Posterior / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D014667:Vasopressins / Q000378:metabolism*
D010446:Peptide Fragments; D014667:Vasopressins; D010121:Oxytocin; D004399:Dynorphins; C026770:dynorphin (1-8)