Plasma growth hormone and prolactin response to FK 33-824, a synthetic opioid agonist, in broiler chickens.
A synthetic opioid agonist, FK 33-824 ([D-Ala2,N-Me-Phe4,Met-(O)5-ol]- enkephalin), was administered intramuscularly at levels of 0, 1, 25, or 625 micrograms/kg of body weight to 4-wk-old Arbor Acres x Arbor Acres broiler cockerels. All levels of FK 33-824 caused the birds to be sedated, with the highest dose causing deep sedation over the 240-min test period. A significant time by treatment interaction was seen for plasma growth hormone (GH). At 30 min after treatment, a significant increase in GH occurred, but this transitory increase returned to control levels at 60 min. A secondary GH peak was observed in the 240-min samples from cockerels given the 625 micrograms/kg dose. Significant treatment and time effects and a time by treatment interaction were seen in the plasma prolactin (PRL) response to FK 33-824. Prolactin was increased at 30 and 60 min after treatment with 1 microgram/kg, whereas higher doses seemed to suppress PRL concentrations. Over the 240-min experimental period, PRL concentrations tended to increase in all treatments except in the treatment with the lowest FK 33-824 dose, but the largest transitory increase was observed at 240 min in the birds given the 625 micrograms/kg dose. These results suggest that FK 33-824 affected GH and PRL secretion in chickens in a manner different from other opioid agonists. This difference was probably due to the ability of FK 33-824 to bind to multiple opiate receptors, with the highest affinity for mu receptors and lesser affinity for delta receptors, whereas other opioids have high affinity for delta receptors.(ABSTRACT TRUNCATED AT 250 WORDS)
Edens
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North Carolina State University, Raleigh 27695-7635.
Parkhurst
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D000818:Animals; D002645:Chickens / Q000097:blood*; D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin / Q000008:administration & dosage*; D013006:Growth Hormone / Q000097:blood* / Q000187:drug effects; D007273:Injections, Intramuscular; D008297:Male; D011388:Prolactin / Q000097:blood* / Q000187:drug effects; D012894:Sleep Stages; D013997:Time Factors
D005405:D-Ala(2),MePhe(4),Met(0)-ol-enkephalin; D011388:Prolactin; D013006:Growth Hormone