title: The differential effects of food restriction on 5-HT1A and 5-HT1B receptor mediated control of serotonergic transmission in the hippocampus and hypothalamus of rats.
abstract: Serotonergic pathways are considered important in the regulation of appetite. We have determined, in female rats, the effects of 4 weeks food restriction (FR) on serotonin function, using in vivo microdialysis. We recorded basal 5-HT release in the hypothalamus and hippocampus, and the sensitivity of the somatodendritic 5-HT1A autoreceptors in the raphe nuclei, and the nerve terminal 5-HT1B autoreceptors which together regulate the synthesis and release of 5-HT in these regions. Sensitivity of the somatodendritic 5-HT1A autoreceptors was assessed by measuring the reduction in extracellular 5-HT induced by systemic administration of the 5-HT1A receptor agonist 8-hydroxy-2-di-n-(propylamino)-tetralin (8-OH-DPAT), while sensitivity of nerve terminal 5-HT1B autoreceptors was measured by observing the increase in 5-HT release after systemic injection of the 5-HT1B receptor antagonist GR 127935. Basal release of 5-HT was not affected by FR. 8-OH-DPAT decreased 5-HT release in the hippocampus and hypothalamus in both groups, while GR 127935 increased 5-HT release in both areas in the control animals but not in the hypothalamus of the FR animals. Since 5-HT1B receptors regulate 5-HT release by a negative feedback mechanism, the decrease in sensitivity of 5-HT1B receptors in the hypothalamus of FR rats indicates increased serotonergic transmission in these rats. The fact that such differential effects on 5-HT release appeared only in the hypothalamus, the center of regulation of energy balance, suggests a compensatory role in FR by increasing 5-HT secretion, thereby reducing feeding behavior.
authors.affiliation: Biological Psychiatry Laboratory, Department of Psychiatry, Hadassah Hospital, POB 12000, Jerusalem 91120, Israel.
authors.forename: Eitan
authors.initials: E
authors.lastname: Gur
authors.forename: Michael E
authors.initials: ME
authors.lastname: Newman
authors.forename: Yosefa
authors.initials: Y
authors.lastname: Avraham
authors.forename: Eliyahu
authors.initials: E
authors.lastname: Dremencov
authors.forename: Elliot M
authors.initials: EM
authors.lastname: Berry
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D001835:Body Weight; D005260:Female; D006624:Hippocampus / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D007031:Hypothalamus / Q000737:chemistry / Q000187:drug effects / Q000502:physiology*; D010069:Oxadiazoles / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology; D051381:Rats; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin / Q000502:physiology*; D044263:Receptors, Serotonin, 5-HT1; D012701:Serotonin / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D012702:Serotonin Antagonists / Q000494:pharmacology; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
chemical_list: D010069:Oxadiazoles; D010879:Piperazines; D044302:Receptor, Serotonin, 5-HT1B; D011985:Receptors, Serotonin; D044263:Receptors, Serotonin, 5-HT1; D012702:Serotonin Antagonists; D017366:Serotonin Receptor Agonists; C090701:GR 127935; D012701:Serotonin; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin