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.
Muñoz-Acedo
G
G
Department of Biochemistry and Molecular Biology, Medical School, University of Alcalá, Madrid, Spain.
López-Sañudo
S
S
Arilla
E
E
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