Alberto Bianchetti

Antidepressant profile in rodents of SR 58611A, a new selective agonist for atypical β-adrenoceptors

beta 2-Adrenoceptor agonists possess antidepressant-like activity in animals and man, but their peripheral side-effects prevent their therapeutic use. Atypical beta-adrenoceptors have not been demonstrated in the central nervous system, but are known to exist in peripheral tissues such as the rat colon. We have now studied the antidepressant-like effects in rodents of a new selective atypical beta-adrenoceptor agonist, SR 58611A. SR 58611A was active with minimal effective doses of 0.1-0.3 mg kg-1 i.p. in several models (antagonism of the hypothermia induced by apomorphine and reserpine; potentiation of the toxicity produced by yohimbine; reversal of learned helplessness), but was inactive in the tests of reserpine-induced ptosis and behavioural despair. The antidepressant-like effect of SR 58611A was not antagonised by selective beta 1- or beta 2-adrenoceptor antagonists, but was blocked by high doses of the non-selective beta-adrenoceptor antagonists, propranolol and alprenolol. Unlike beta 2-adrenoceptor agonists, SR 58611A did not reduce locomotor activity or increase water intake at doses up to 10 mg kg-1. Therefore, SR 58611A may represent the prototype of a new class of antidepressant compounds.

Reduction of normal food intake in rats and dogs and inhibition of experimentally induced hyperphagia in rats by CM 57373 and fenfluramine

The anorectic effect of CM 57373 in dogs and in rats food-deprived or with experimentally induced hyperphagia (cafeteria-diet hyperphagia and insulin hyperphagia) was compared to the effect of serotoninergic anorectic drug dl-fenfluramine. CM 57373 and dl-fenfluramine administered orally caused a dose-related reduction of food consumption by food-deprived rats (ID50 = 7.4 mg/kg and 2.5 mg/kg respectively). The oral ID50 in dogs was 2.4 mg/kg for CM 57373 and 1.1 mg/kg for dl-fenfluramine. This animal species tolerated CM 57373 better than dl-fenfluramine. The latter induced mydriasis, dyskinesia and reduced spontaneous activity. The anorectic effects of CM 57373 and dl-fenfluramine in cafeteria-diet hyperphagic rats were comparable. Tolerance to the anorectic effect developed in rats treated with both CM 57373 and dl-fenfluramine although tolerance was initially less pronounced with CM 57373 than dl-fenfluramine. The brain serotonin levels of cafeteria-fed rats were unchanged by CM 57373 throughout treatment whereas dl-fenfluramine decreased the monoamine levels starting from the 8th day. Both drugs reduced 5-hydroxyindolacetic acid levels. CM 57373 (7.4 mg/kg p.o.) and dl-fenfluramine (2.5 mg/kg p.o.) markedly reduced the overeating caused by insulin injection. These results indicate that CM 57373 shows several characteristics of drugs that act via serotonin to depress food intake in various animal species.