title: The effects of metergoline and 8-OH-DPAT injections into arcuate nucleus and lateral hypothalamic area on feeding in female rats during the estrous cycle.
abstract: The present study examined the effects of local injections of metergoline (MET, an antagonist of 5-HT1/2 receptors, 2 and 20 nmol) and 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT, selective 5-HT1A receptor agonist, 0.6 and 6 nmol) into the arcuate nucleus (ARC) and the lateral hypothalamus (LH), on ingestive and non-ingestive behaviors of female rats. These effects were examined during the diurnal periods of diestrus and estrus in rats adapted to eat a wet mash diet (enriched with 10% sucrose) during 1h for 3 consecutive days at the recording chamber. The results showed that 8-OH-DPAT injected into the LH significantly reduced food intake at all doses and both cycle stages, while in the ARC these treatments evoked hypophagia only at the highest 8-OH-DPAT dose and only at the estrous phase. MET administered into the ARC (at all doses) failed to affect food intake during both estrous stages. On the other hand, food intake decreased after injection of both doses of MET into the LH of rats during estrous and diestrus phases. In estrus stage, injections of the higher dose of 8-OH-DPAT into the ARC and into the LH decreased the duration of feeding. Latency to start feeding, drinking, and non-ingestive behaviors were not affected by 8-OH-DPAT or MET treatments in the ARC or the LH in both cycle phases. These results indicated that 5-HT1A receptors participate in the serotonergic control of feeding-related mechanisms located at the ARC and the LH. These feeding-related serotonergic circuits in both areas are possibly affected by ovarian hormones that could increase sensitivity of ARC neurons to the hypophagic effects of 8-OH-DPAT or increase the efficacy of satiety signals that terminate feeding. In addition, the present data indicated that serotonergic inputs do not exert a tonic inhibitory activity on the ARC and the LH feeding-related circuits.
authors.affiliation: Department of Physiological Sciences, Centre of Biological Sciences, Federal University of Santa Catarina (UFSC), Florianópolis, SC, Brazil.
authors.forename: Sérgio Murilo
authors.initials: SM
authors.lastname: Steffens
authors.forename: Isabel Cristina
authors.initials: IC
authors.lastname: da Cunha
authors.forename: Danielle
authors.initials: D
authors.lastname: Beckman
authors.forename: Ana Paula Fraga
authors.initials: AP
authors.lastname: Lopes
authors.forename: Moacir Serralvo
authors.initials: MS
authors.lastname: Faria
authors.forename: José
authors.initials: J
authors.lastname: Marino-Neto
authors.forename: Marta Aparecida
authors.initials: MA
authors.lastname: Paschoalini
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology*; D000818:Animals; D001522:Behavior, Animal; D004305:Dose-Response Relationship, Drug; D004435:Eating / Q000187:drug effects; D030762:Estrous Cycle / Q000502:physiology*; D005247:Feeding Behavior / Q000187:drug effects*; D005260:Female; D007026:Hypothalamic Area, Lateral / Q000187:drug effects*; D008711:Metergoline / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D012702:Serotonin Antagonists / Q000494:pharmacology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology*
chemical_list: D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; D008711:Metergoline; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin