title: Central NPY-Y5 receptors activation plays a major role in fasting-induced pituitary-thyroid axis suppression in adult rat.
abstract: Neuropeptide Y (NPY) inhibits TRH neurons in fed state, and hypothalamic NPY higher expression during fasting has been proposed to be involved in fasting-induced suppression of the hypothalamus-pituitary-thyroid (HPT) axis. We investigated the role of central Y5 receptors in the control of thyrotropin (TSH) and thyroid hormone (TH) secretion. Fed and fasting rats received twice daily central injections (3rd ventricle) of Y5 receptor antagonist (CGP71683; 15nmol/rat) for 72h. Fasted rats also received a single central injection of CGP71683 (15nmol/rat) at the end of 72h of fasting. In fed rats, Y5 receptor blockade reduced total food intake by 32% and body mass by almost 10% (p<0.01), corroborating the role of this receptor in food intake control. 72h-fasted rats exhibited a 4-fold increase in serum TSH (p<0.001), 1h after a single injection of Y5 antagonist. Also with multiple injections during 72h of fasting, Y5 blockade resulted in activation of thyroid axis, as demonstrated by a 3-times rise in serum T4 (p<0.001), accompanied by unchanged TSH and T3. In fed rats, the chronic central administration of CGP71683 resulted in reduced total serum T4 without changes in free T4 and TSH. Serum leptin and PYY were not altered by the NPY central blockade in both fed and fasted rats, suggesting no role of these hormones in the alterations observed. Therefore, the inhibition of central Y5 neurotransmission resulted in activation of thyroid axis during fasting suggesting that NPY-Y5 receptors contribute to fasting-induced TSH and TH suppression.
authors.affiliation: Biophysics Institute Carlos Chagas Filho, Federal University of Rio de Janeiro, 21941-902, Rio de Janeiro, RJ, Brazil.
authors.forename: Ricardo Henrique
authors.initials: RH
authors.lastname: Costa-e-Sousa
authors.forename: Luana Lopes
authors.initials: LL
authors.lastname: Souza
authors.forename: Camila
authors.initials: C
authors.lastname: Calviño
authors.forename: Adriana
authors.initials: A
authors.lastname: Cabanelas
authors.forename: Norma Aparecida Santos
authors.initials: NA
authors.lastname: Almeida
authors.forename: Karen Jesus
authors.initials: KJ
authors.lastname: Oliveira
authors.forename: Carmen Cabanelas
authors.initials: CC
authors.lastname: Pazos-Moura
mesh_terms: D000818:Animals; D005215:Fasting / Q000009:adverse effects / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism / Q000473:pathology; D020738:Leptin / Q000097:blood; D009281:Naphthalenes / Q000494:pharmacology; D009478:Neuropeptide Y / Q000037:antagonists & inhibitors / Q000378:metabolism; D010913:Pituitary-Adrenal System / Q000378:metabolism / Q000473:pathology*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D017476:Receptors, Neuropeptide Y / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013963:Thyroid Hormones / Q000097:blood / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood / Q000378:metabolism*
chemical_list: D020738:Leptin; D009281:Naphthalenes; D009478:Neuropeptide Y; D011743:Pyrimidines; D017476:Receptors, Neuropeptide Y; D013963:Thyroid Hormones; C100568:neuropeptide Y5 receptor; C116786:CGP 71683 A; D013972:Thyrotropin