ly-53857 and 1-(3-trifluoromethylphenyl)piperazine

The receptors involved in the bronchoconstriction evoked in vivo by intravenous administration to the anesthetized guinea pig of serotonin and serotonin-related agonists have been examined in this study. Animals were pretreated with indomethacin and (+/-)-propranolol to inhibit cyclooxygenase and beta adrenergic receptors, respectively, and pulmonary parameters were obtained with a Buxco pulmonary mechanics computer. Dose-dependent increases in pulmonary resistance and decreases in dynamic lung compliance were produced by serotonin, 2-methyl-serotonin, 5-methoxy-tryptamine, alpha-methyl-serotonin, 5-carboxamidotryptamine, and m-trifluoromethylphenylpiperazine (TFMPP). Responses to all agonists except 2-methyl-serotonin, a selective 5-hydroxytryptamine3 (5-HT3) agonist, were antagonized by the 5-HT2 antagonists, LY53857 and ketanserin. Zaclopride, 1 and 10 mg/kg, a selective 5-HT3 antagonist, blocked responses to 2-methyl-serotonin. A maximally effective dose of LY53857 (1 mg/kg) produced larger shifts of the dose-response curves to serotonin, 5-methoxytryptamine and alpha-methyl-serotonin than did a maximally effective dose of ketanserin (1 mg/kg). Thiorphan, 10 mg/kg, an inhibitor of neutral endopeptidase, potentiated 2-methyl-serotonin and, when studied in the presence of LY53857, also potentiated serotonin, 5-methoxytryptamine and TFMPP. After thiorphan and LY53857, responses to serotonin, but not 5-methoxytryptamine or TFMPP, were blocked by zaclopride. Capsaicin pretreatment of the animals resulted in rightward shifts of the dose-response curves to serotonin, 2-methyl-serotonin and TFMPP, but not to 5-methoxytryptamine or alpha-methyl-serotonin. Potentiation by thiorphan and antagonism by zaclopride of responses to serotonin were still evident after capsaicin pretreatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Anesthesia; Animals; Atropine; Benzamides; Bridged Bicyclo Compounds; Bridged Bicyclo Compounds, Heterocyclic; Bronchoconstriction; Capsaicin; Dose-Response Relationship, Drug; Ergolines; Guinea Pigs; Male; Piperazines; Pyrilamine; Receptors, Serotonin; Serotonin; Serotonin Antagonists; Thiorphan

8-OH-DPAT (2.5-10 mg/kg) and buspirone (10 mg/kg) but not 5,7-DHT (200 micrograms/mouse), pCPA (75 and 150 mg/kg, three times), ritanserin (0.1 and 0.2 mg/kg), LY 53857 (1.5 and 3 mg/kg), GR 38032 F (0.1-100 micrograms/kg), TFMPP (5 and 20 mg/kg) and mCPP (2.5 and 5 mg/kg) antagonized the rise in body temperature that occurs to the last mice removed from their group housing, which was termed as stress-induced hyperthermia (SIH). Ro 15-1788, at a dose which blocked the effect of diazepam on SIH, did not reverse the anxiolytic effect of buspirione. Instead, when cerebral 5-HT content was reduced to 50% by 5,7-DHT-induced lesion, the effect of buspirone on SIH was decreased. TFMPP 5 mg/kg did not shorten significantly the onset of SIH as could have been expected by an anxiogenic drug, while the dose of 20 mg/kg did not modify the pattern of SIH at all. The lower dose of TFMPP evoked a hyperthermic and the higher a hypothermic response.

Topics: 5,7-Dihydroxytryptamine; 8-Hydroxy-2-(di-n-propylamino)tetralin; Animals; Anti-Anxiety Agents; Body Temperature Regulation; Buspirone; Diazepam; Ergolines; Fenclonine; Fever; Flumazenil; Imidazoles; Male; Mice; Ondansetron; Piperazines; Piperidines; Ritanserin; Serotonin; Serotonin Antagonists; Stress, Psychological; Tetrahydronaphthalenes

Administration of the 5-HT1C/5-HT2 receptor agonist 1-(2,5-dimethoxy-4- iodophenyl)-2-aminopropane (DOI, 0.125-2.0 mg/kg i.v.) triggered dose-dependent increases in plasma glucose; plasma insulin levels remained unchanged. Pretreatment with the 5-HT1C/5-HT2 receptor antagonists LY 53857, ritanserin, or the mixed 5-HT2/alpha 1-adrenoceptor antagonist ketanserin either diminished or prevented the hyperglycemic effect of DOI (0.5 mg/kg). Administration of the mixed 5-HT1C receptor agonists/5-HT2 receptor antagonists 1-(3-chlorophenyl)-piperazine (mCPP) or 1-(3-trifluoromethyl)phenyl)piperazine level (TFMPP) did not affect plasma glucose levels. However, pretreatment with mCPP or TFMPP decreased DOI-induced hyperglycemia in a dose-dependent manner. The alpha 2-adrenoceptor antagonist idazoxan and the ganglionic blocker hexamethonium both decreased DOI-induced hyperglycemia, Whilst the alpha 1-adrenoceptor antagonist prazosin amplified the rise in plasma glucose elicited by DOI. The peripherally acting 5-HT1C/5-HT2 receptor agonist alpha-methyl-5-HT (0.5-1.0 mg/kg i.v.) triggered a rise in plasma glucose levels that was associated with an increase in plasma insulin levels. Pretreatment with LY 53857 diminished alpha-methyl-5-HT-induced hyperglycemia. These data indicate that 5-HT2 receptors, but not 5-HT1C receptors, and catecholaminergic systems, mediate DOI-induced hyperglycemia. Moreover, it is suggested that the inhibition of insulin release by DOI is centrally mediated, and that activation of peripheral 5-HT2 receptors may affect glycemia.

Topics: Amphetamines; Animals; Blood Glucose; Catecholamines; Ergolines; Hyperglycemia; Insulin; Male; Piperazines; Piperidines; Rats; Rats, Inbred Strains; Receptors, Serotonin; Ritanserin; Serotonin