Stimulation of crop sac and pituitary lactotrophs after intraventricular administration of dermorphin in pigeons

The dermorphin peptide family

1. In 1980, the skin of certain frogs belonging to the genus Phyllomedusinae was found to contain two new peptides that proved to be selective mu-opioid agonists. Given the name dermorphins, these were the first members of a peptide family that in the past 15 years has grown to reach a total of seven naturally occurring peptides and nearly 30 synthetic analogs. 2. Dermorphin peptides are potent analgesics in rodents and primates, including man. Some dermorphins can enter the blood-brain barrier and produce central antinociception after peripheral administration. 3. The dermorphin family also includes mu 1-opioid receptor selective agonists that produce intense opioid analgesia, but stimulate pulmonary ventilation. 4. Experiments in rats and mice chronically exposed to dermorphins have shown that not only do they have higher antinociceptive efficacy and potency than morphine, but they are also less likely than morphine to produce tolerance, dependence and opiate side effects.

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)

Vasoactive intestinal polypeptide stimulates prolactin release in vivo in the ring dove (Streptopelia risoria)

I.v. administration of vasoactive intestinal polypeptide (VIP) to ring doves significantly elevated the plasma concentration of prolactin after 10 min in a dose-related manner. The plasma prolactin concentration of nonbreeding doves with low basal levels was increased by a similar amount as in brooding doves whose initially high concentration of plasma prolactin had been reduced by nest deprivation prior to treatment.