Mediation of the behavioral, endocrine and thermoregulatory actions of ghrelin.
The action of ghrelin on telemetrically recorded motor activity and the transmission of the effects of this neuropeptide on spontaneous and exploratory motor activity and some related endocrine and homeostatic parameters were investigated. Different doses (0.5-5 microg) of ghrelin administered intracerebroventricularly caused significant increases in both square crossing and rearing activity in the "open-field" apparatus, while only the dose of 5 microg evoked a significant increase in the spontaneous locomotor activity recorded by telemetry. Ghrelin also induced significant increases in corticosterone release and core temperature. To determine the transmission of these neuroendocrine actions, the rats were pretreated with different antagonists, such as a corticotropin-releasing hormone (CRH) antagonist (alpha-helical CRH(9-41)), the nitric oxide synthase inhibitor Nomega-nitro-L-arginine-methyl ester (L-NAME), haloperidol, cyproheptadine or the cyclooxygenase inhibitor noraminophenazone (NAP). The open-field and biotelemetric observations revealed that the motor responses were diminished by pretreatment with the CRH antagonist and haloperidol. In the case of HPA (hypothalamic pituitary adrenal) activation, only cyproheptadine pretreatment proved effective; haloperidol and L-NAME did not modify the corticosterone response. NAP had only a transient, while cyproheptadine elicited a more permanent impact on the hyperthermic response evoked by ghrelin; the other antagonists proved to be ineffective. The present data suggest that both CRH release and dopaminergic transmission may be involved in the ghrelin-evoked behavioral responses. On the other hand, ghrelin appears to have an impact on the HPA response via a serotonergic pathway and on the hyperthermic response via a cyclooxygenase and a serotonergic pathway.
Jászberényi
M
M
Department of Pathophysiology, University of Szeged, Neurohumoral Research Group, Hungarian Academy of Sciences, PO Box 427, Semmelweis u. 1, H-6701 Szeged, Hungary.
Bujdosó
E
E
Bagosi
Z
Z
Telegdy
G
G
D000632:Aminopyrine / Q000494:pharmacology; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001833:Body Temperature Regulation / Q000187:drug effects*; D003345:Corticosterone / Q000097:blood; D003346:Corticotropin-Releasing Hormone / Q000097:blood; D016861:Cyclooxygenase Inhibitors / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004703:Endocrine System / Q000187:drug effects*; D054439:Ghrelin; D007030:Hypothalamo-Hypophyseal System / Q000187:drug effects; D007276:Injections, Intraventricular; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000097:blood; D009043:Motor Activity / Q000187:drug effects; D009478:Neuropeptide Y / Q000097:blood; D009569:Nitric Oxide / Q000378:metabolism; D036361:Peptide Hormones / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000378:metabolism
D016861:Cyclooxygenase Inhibitors; D054439:Ghrelin; D009478:Neuropeptide Y; D036361:Peptide Hormones; D000632:Aminopyrine; D009569:Nitric Oxide; D012701:Serotonin; D009074:Melanocyte-Stimulating Hormones; D003346:Corticotropin-Releasing Hormone; D004298:Dopamine; D003345:Corticosterone