Modulation by isoproterenol and propranolol of somatostatin receptors in synaptosomes from rat frontoparietal cortex.
DL-Propranolol (PRO), a beta-adrenergic blocking agent, and the neuropeptide somatostatin (SS) have central nervous system depressant and anticonvulsive properties. To investigate a possible relationship between these two components, we studied the influence of PRO and DL-isoproterenol (ISO), a beta-adrenergic agonist, on the somatostatinergic system in the rat frontoparietal cortex. The short- (5 h) and long-term (14 days) administration of ISO (5 mg/kg, intraperitoneally (i.p.)), or of PRO (10 mg/kg, i.p.) did not affect somatostatin-like immunoreactivity (SLI) content in the frontoparietal cortex of male Wistar rats. Both short- and long-term ISO administration decreased the number of specific [125I]Tyr11-SS receptors in synaptosomes from frontoparietal cortex (31%, P < 0.05, and 26%, P < 0.02, after short- and long-term administration, respectively) without changing the affinity constant. This decrease in the number of [125I]Tyr11-SS receptors was not due to a direct effect of ISO on these receptors since no decrease in binding was produced by high concentrations of ISO (10(-5) M) when added in vitro. This decrease could be blocked by pretreatment with PRO. Short- and long-term administration of PRO alone produced an increase in the [125I]Tyr11-SS binding in frontoparietal cortex (26%, P < 0.02, and 40%, P < 0.001, after short- or long-term administration, respectively) without changing the affinity constant.
López-Sañudo
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Department of Biochemistry and Molecular Biology, Medical School, University of Alcalá, Madrid, Spain.
Arilla
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D000818:Animals; D005625:Frontal Lobe / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D010296:Parietal Lobe / Q000187:drug effects / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology*; D011863:Radioimmunoassay; D051381:Rats; D017208:Rats, Wistar; D017481:Receptors, Somatostatin / Q000187:drug effects*; D013004:Somatostatin / Q000031:analogs & derivatives / Q000276:immunology / Q000378:metabolism; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism*
D017481:Receptors, Somatostatin; D013004:Somatostatin; C032367:somatostatin, Tyr(11)-; D011433:Propranolol; D007545:Isoproterenol