Effects of central infusions of neuropeptide Y on the somatotropic axis in sheep fed on two levels of protein.
Effects of infusions of neuropeptide Y (NPY) into 3rd ventricle of growing sheep fed on diets containing restricted (R) or elevated (E) levels of protein on the immunoreactive (ir) somatostatin neurones, ir somatotrophs, growth hormone (GH) concentration in the blood plasma were studied. The long-term restriction of protein in the diet elicited: enhancing irSS content in periventricular perikarya; diminishing irSS stores in the median eminence and elevating the number ir somatotrophs and content of irGH. NPY infusions enhanced the content of irSS in perikarya in sheep fed on E diet and diminished the number of ir somatotrophs and content of irGH of sheep fed on R diet. The R diet as well as NPY infusions caused an increase in GH mean concentrations in the blood plasma. Obtained results suggest that stimulatory effect of restricted feeding and/or NPY action on GH secretion can be due to attenuated SS output. Since dietary restrictions and exogenous NPY have similar influence on the activation of GH secretion, we suggest that NPY could be a neuromodulatory link between nutritional cues and somatotropic axis in sheep.
Gładysz
A
A
Kielanowski Institute of Animal Physiology and Nutrition, Polish Academy of Sciences, 05-110 Jabłonna, Poland.
Krejci
P
P
Simůnek
J
J
Polkowska
J
J
D000818:Animals; D001835:Body Weight; D018753:Diet, Protein-Restricted; D004044:Dietary Proteins / Q000494:pharmacology*; D005260:Female; D013006:Growth Hormone / Q000032:analysis / Q000097:blood*; D007030:Hypothalamo-Hypophyseal System / Q000737:chemistry / Q000187:drug effects*; D007276:Injections, Intraventricular; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism; D008473:Median Eminence / Q000737:chemistry / Q000187:drug effects; D009478:Neuropeptide Y / Q000494:pharmacology*; D010286:Paraventricular Hypothalamic Nucleus / Q000737:chemistry / Q000187:drug effects; D010903:Pituitary Gland, Anterior / Q000737:chemistry / Q000187:drug effects; D011502:Protein-Energy Malnutrition / Q000097:blood / Q000503:physiopathology; D012756:Sheep; D013004:Somatostatin / Q000032:analysis / Q000378:metabolism
D004044:Dietary Proteins; D009478:Neuropeptide Y; D013004:Somatostatin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone