title: Involvement of 5-HT1A- and alpha 2-receptors in the decreased 5-hydroxytryptamine release and metabolism in rat suprachiasmatic nucleus after intravenous 8-hydroxy-2-(n-dipropylamino) tetralin.
abstract: The 5-hydroxytryptamine1A-receptor agonist 8-hydroxy-2-(n-dipropylamino) tetralin (8-OH-DPAT, 0.1 mg kg-1 i.v.) decreased the height of the extracellular 5-hydroxyindoleacetic acid (5-HIAA) oxidation peak recorded in the suprachiasmatic nucleus (SCN) of the anaesthetized rat by use of differential pulse voltammetry. The decrease in extracellular 5-HIAA produced by 8-OH-DPAT could be partially attenuated by prior administration of the non-selective 5-HT receptor antagonist methiothepin (1 mg kg-1 i.v.). The 5-HT2-receptor antagonist ritanserin (0.2 mg kg-1 i.v.) did not appear to block the effects of 8-OH-DPAT. The selective ligand for 5-HT1A recognition sites TVX Q 7821 (isapirone, 1 mg kg-1 i.v.) decreased the extracellular level of 5-HIAA in the SCN but to a lesser extent than 8-OH-DPAT. The response to 8-OH-DPAT was attenuated by prior administration of TVX Q 7821 to a level suggesting that TVX Q 7821 had blocked the effect of intravenous 8-OH-DPAT. Idazoxan (0.2 mg kg-1 i.v.) an alpha 2-adrenoceptor antagonist, completely blocked the effect of 8-OH-DPAT on the 5-HIAA oxidation peak recorded in the SCN, whilst having no effect on the 5-HIAA oxidation peak when given alone. At a dose of 0.5 mg kg-1 i.v. idazoxan induced a 120% increase in the height of the indole oxidation peak, suggesting that 5-HT release and metabolism in the rat SCN may be influenced by tonic adrenergic inputs. The data in this paper suggest that 5-HT1A- and alpha 2-receptors are involved in the effects of i.v. administered 8-OH-DPAT on 5-HT release and metabolism in the SCN in vivo.
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology; D004146:Dioxanes / Q000494:pharmacology; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D019329:Idazoxan; D008297:Male; D008719:Methiothepin / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology*; D011743:Pyrimidines / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D011985:Receptors, Serotonin / Q000502:physiology*; D012701:Serotonin / Q000378:metabolism*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000378:metabolism*; D013764:Tetrahydronaphthalenes / Q000494:pharmacology*
chemical_list: D014151:Anti-Anxiety Agents; D004146:Dioxanes; D009281:Naphthalenes; D011743:Pyrimidines; D011942:Receptors, Adrenergic, alpha; D011985:Receptors, Serotonin; D013764:Tetrahydronaphthalenes; D012701:Serotonin; D006897:Hydroxyindoleacetic Acid; D008719:Methiothepin; C043077:ipsapirone; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D019329:Idazoxan