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Endorphinergic regulation of feeding in the pigeon
1539
H27 SEK-LINKED DWARFISM AN'D DIETARY THYROID HORMONES ALTER TRH-MEDIATED GROWTH HORMONE SECRETION IN BROILER CHICKENS. R. J. Denver*, S. J. Bowen and C. G. Scanes. Department of Animal Sciences, Rutgers - The State University, New Brunswick, New Jersey 08903. The effects of tri-iodothyronine fT ) and thyroxine (T ) on thyro) secretfon tt-ophinreleasing hormone (TRH) mediated growth hormone (Gfi were investigated in sex-linked dwarf and normal broiler chickens. The genotypes studied were normal females (Dw-), normal m&es (DwDw), hemizygous dwarf females (dw-) and heterozygous dwarf males (Dw dw). Upon hatching the birds were randomly assigned to dietary treatments consisting of T3 (1 ppm), T (1 ppm) and a control diet. At 4, 8 and 12 weeks of age a random sampi-' e of chickens from each treatment group were prebled, injected with TRH (10 ng/kg i.v.) and bled repeatedly at 10, 30 and 60 minutes after injections. The concentration of GH in each sample was measured by radioimmunoassay. In the control and T treated birds the plasma concentration of GH was greatly increased with& 10 minutes of the injection of TRH; the greatest effect being observed at 8 weeks of age, Dietary T3 effectively inhibited TRH-mediated GH secretion in all genotypes at all ages. T was much less effective than T in inhibiting TRHmediated GH secretioi; the magnitude of this inhi2 ition varying with genotype and age. In the Dwdw and dw- genotypes the GH response to TRH was greater than the other genotypes at 12 weeks. The return of plasma GH to basal levels in the dw- pullets was slower than the other genotypes. The present results demonstrate that the thyroid hormones inhibit TRH-mediated GH secretion in the domestic fowl. Differences in the inhibitory effects of T3 and T4 suggests a greater biological activity of T3 at the level of the pituitary.
H28
ENDORPHINERGIC REGULATION OF FEEDING IN THE PIGEON. P. Deviche* RuhrUniversity Bochum, Dept. of Experimental Animal Psychology, 4630 Bochum 1, FRG. A series of experiments was performed in order to evaluate the hypothesis that the feeding system of domestic pigeons involves endogenous opioids. (A) Peripheral treatment with the opiate antagonist naloxone dose-dependently reduced feeding. (B) A small dose (25 ug) of naloxone was more efficient in decreasing feeding when administered centrally (icv) then peripherally, suggesting the involvement of a central mechanism in the effect of the drug. (C) The other opiate antagonist MR2266 also attenuated feeding; this influence was not produced by its stereoisomer MR2267, confirming the participation of opiate receptors in the opiate antagonist-produced anorexia. (D) Central injection of b-endorphin strongly promoted feeding. At the dose of 1.5 nmoles, ostrich b-endorphin was more potent in this respect than human b-endorphin, thus paralleling a difference in the affinity for the brain opiate receptors between the two peptides. (E) The described alterations of feeding were not concurrent with variations of the fluid intake, showing the behavioral specificity of the effects. Altogether, it therefore appears that pigeons possess a food promoting central mechanism involving the endogenous opiates.
H27 SEK-LINKED DWARFISM AN'D DIETARY THYROID HORMONES ALTER TRH-MEDIATED GROWTH HORMONE SECRETION IN BROILER CHICKENS. R. J. Denver*, S. J. Bowen and C. G. Scanes. Department of Animal Sciences, Rutgers - The State University, New Brunswick, New Jersey 08903. The effects of tri-iodothyronine fT ) and thyroxine (T ) on thyro) secretfon tt-ophinreleasing hormone (TRH) mediated growth hormone (Gfi were investigated in sex-linked dwarf and normal broiler chickens. The genotypes studied were normal females (Dw-), normal m&es (DwDw), hemizygous dwarf females (dw-) and heterozygous dwarf males (Dw dw). Upon hatching the birds were randomly assigned to dietary treatments consisting of T3 (1 ppm), T (1 ppm) and a control diet. At 4, 8 and 12 weeks of age a random sampi-' e of chickens from each treatment group were prebled, injected with TRH (10 ng/kg i.v.) and bled repeatedly at 10, 30 and 60 minutes after injections. The concentration of GH in each sample was measured by radioimmunoassay. In the control and T treated birds the plasma concentration of GH was greatly increased with& 10 minutes of the injection of TRH; the greatest effect being observed at 8 weeks of age, Dietary T3 effectively inhibited TRH-mediated GH secretion in all genotypes at all ages. T was much less effective than T in inhibiting TRHmediated GH secretioi; the magnitude of this inhi2 ition varying with genotype and age. In the Dwdw and dw- genotypes the GH response to TRH was greater than the other genotypes at 12 weeks. The return of plasma GH to basal levels in the dw- pullets was slower than the other genotypes. The present results demonstrate that the thyroid hormones inhibit TRH-mediated GH secretion in the domestic fowl. Differences in the inhibitory effects of T3 and T4 suggests a greater biological activity of T3 at the level of the pituitary.
H28
ENDORPHINERGIC REGULATION OF FEEDING IN THE PIGEON. P. Deviche* RuhrUniversity Bochum, Dept. of Experimental Animal Psychology, 4630 Bochum 1, FRG. A series of experiments was performed in order to evaluate the hypothesis that the feeding system of domestic pigeons involves endogenous opioids. (A) Peripheral treatment with the opiate antagonist naloxone dose-dependently reduced feeding. (B) A small dose (25 ug) of naloxone was more efficient in decreasing feeding when administered centrally (icv) then peripherally, suggesting the involvement of a central mechanism in the effect of the drug. (C) The other opiate antagonist MR2266 also attenuated feeding; this influence was not produced by its stereoisomer MR2267, confirming the participation of opiate receptors in the opiate antagonist-produced anorexia. (D) Central injection of b-endorphin strongly promoted feeding. At the dose of 1.5 nmoles, ostrich b-endorphin was more potent in this respect than human b-endorphin, thus paralleling a difference in the affinity for the brain opiate receptors between the two peptides. (E) The described alterations of feeding were not concurrent with variations of the fluid intake, showing the behavioral specificity of the effects. Altogether, it therefore appears that pigeons possess a food promoting central mechanism involving the endogenous opiates.