Reduction of somatostatin receptors in rat hippocampus by treatment with 5,7-dihydroxytryptamine.
Several lines of evidence suggest that somatostatin (SS) may interact with serotonergic neurons in the central nervous system. To assess whether SS acts presynaptically on serotonin (5-hydroxytryptamine, (5-HT)) neurons, SS receptors were measured in membranes from the hippocampus, a brain region that receives dense serotonergic innervation and has a high number of SS receptors in control and 5,7-dihydroxytryptamine (5,7-DHT)-treated rats, at 1 and 3 weeks after injection. Intracerebroventricular (i.c.v.) injection of the 5-HT-specific neurotoxin 5,7-DHT (11 micrograms (free base) dissolved in 10 microliters of isotonic saline containing 0.01% ascorbic acid) produced a 70% reduction in hippocampal 5-HT content at 3 weeks after injection but not at 1 week. This change was associated with a significant decrease in SS receptor density in rat hippocampus only at 3 weeks following the injection, without influencing the apparent affinity of the receptors at any time. Administration of 5,7-DHT did not affect somatostatin-like immunoreactivity (SSLI) levels at both times studied. These results suggest that some of the hippocampal SS receptors may be localized presynaptically on the serotonergic nerve terminals.
Department of Biochemistry and Molecular Biology, Medical School, University of Alcalá, Madrid, Spain.
G
G
Muñoz-Acedo
S
S
López-Sañudo
E
E
Arilla
D015116:5,7-Dihydroxytryptamine / Q000494:pharmacology*; D000818:Animals; D003891:Desipramine / Q000494:pharmacology; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism*; D007276:Injections, Intraventricular; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009411:Nerve Endings / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D017481:Receptors, Somatostatin / Q000378:metabolism*; D012701:Serotonin / Q000276:immunology / Q000378:metabolism; D013004:Somatostatin / Q000378:metabolism
D017481:Receptors, Somatostatin; D015116:5,7-Dihydroxytryptamine; D012701:Serotonin; D013004:Somatostatin; D003891:Desipramine