Dynorphin modulates prolactin secretion in the turkey.
Big dynorphin (prodynorphin 209-240), dynorphin A (prodynorphin 209-225), dynorphin B (prodynorphin 228-240), beta-endorphin (beta-lipotrophin 61-90), or Met-enkephalin, each infused into the third ventricle, were tested for their effect on PRL release in the anesthetized turkey hen. Laying hens that received big dynorphin at the rate of 0.35 nmol/min showed a 5.1-fold increase in serum PRL at the end of a 30-min infusion period. In a second experiment, the big dynorphin-induced PRL increase was 2.6-fold. Nest-deprived, previously incubating hens that received big dynorphin displayed an 8.2-fold increase in serum PRL. Laying and nest-deprived incubating control birds infused with saline displayed no PRL increases. Laying hens that received dynorphin A (0.35 nmol/min) showed a 1.5-fold increase in serum PRL after 30 min of infusion; after 40 min of infusion, this increase rose to 2.7-fold. Infusions of beta-endorphin (0.35 nmol/min), or Met-enkephalin (0.35 nmol/min) failed to evoke PRL increases in either laying or nest-deprived incubating turkeys. Infusion of big dynorphin or dynorphin A for 120 min maintained an elevated PRL level across the period, a level equal to that evoked by electrical stimulation of the medial preoptic nucleus (ES/POM). Infusion of dynorphin B (0.48 nmol/min) or a reduced dose of dynorphin A (0.09 nmol/min) augmented the PRL response evoked by ES/POM. No augmentation was noted for beta-endorphin or Met-enkephalin, nor for saline-infused controls. The dynorphin-induced PRL response appeared to be dose-dependent.(ABSTRACT TRUNCATED AT 250 WORDS)
Youngren
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Department of Ecology, Evolution, & Behavior, University of Minnesota, St. Paul 55108.
Silsby
J L
JL
Phillips
R E
RE
el Halawani
M E
ME
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000008:administration & dosage / Q000494:pharmacology*; D004558:Electric Stimulation; D004744:Enkephalin, Methionine / Q000494:pharmacology; D004745:Enkephalins / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D007700:Kinetics; D011388:Prolactin / Q000378:metabolism*; D011498:Protein Precursors / Q000008:administration & dosage / Q000494:pharmacology; D014422:Turkeys / Q000502:physiology*; D001615:beta-Endorphin / Q000494:pharmacology
D004745:Enkephalins; D011498:Protein Precursors; D004744:Enkephalin, Methionine; D001615:beta-Endorphin; D004399:Dynorphins; D011388:Prolactin; C033660:preproenkephalin