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Biomedical subjects

F Zonta

Publications and source records attributed to F Zonta.

At least 55 records · Page 3Linked to original sources
PubMed1980

[Maximal response of the rat vas deferens. II. Studies on the effect of variations in external K+ and the response to noradrenaline of preparations which were depolarized and exposed to various concentrations of extracellular Ca+].

The mechanical response of the rat vas deferens observed following administration of single or cumulative doses of K+ was studied and then the influence of external Ca2+ on the K+ response was investigated. The response of the preparation to noradrenalin when the concentration of K+ and/or Ca2+ is different from the physiological one was also studied. The results indicate that the ability of K+ to increase free intracellular Ca2+ concentration is greater than that of noradrenalin; there is an increase in the maximal response to noradrenalin on increasing the external concentration of K+ and/or Ca2+.

Animals↗
PubMed1980

[Maximal response of the rat vas deferens. III. Effect of compounds with various pharmacological activities on the response to noradrenaline].

A study has been made of the action on the rat vas deferens response to noradrenalin of the following substances: cocaine, phentolamine and dihydroergocrystine; pronethalol, dichloroisopropylnoradrenalin, propranolol, N-isopropyl-p-nitrophenylethanolamine; d-chlorpheniramine; cimetidine; amitryptyline. With the exception of the beta-adrenolytic agents and cimetidine, all the compounds tested independently of their "principal" pharmacological action showed a property in common with the local anesthetics: depending on dose they were able to increase or decrease the maximal response to noradrenalin. These effects were correlated with variations in the state of stabilization of the membrane.

Animals↗
PubMed1980

Action of local anesthetics on basal tone of rat vas deferens and on response to norepinephrine and calcium.

The actions of three local anesthetics (cocaine, procaine and tetracaine) on basal tone of isolated vas deferens from control and reserpinized rats were studied. The influence of these anesthetics on responses to norepinephrine and calcium was also examined. Cocaine, procaine and tetracaine, in the order, induced phasic and tonic contractions, the latter ones probably due to catecholamine release. The local anesthetics, at the lowest doses, produced an elevation of the maximum response to norepinephrine, as well as a leftward shift of the dose-response curve. The highest doses of local anesthetics inhibited the response to norepinephrine in a non-competitive way, while the response to calcium was competitively inhibited. In this connection, tetracaine proved to be the most active compound. The distinction between destabilizing and stabilizing effects on membrane is pointed out and discussed.

Anesthetics, Local↗
PubMed1977

[Pharmacologic peculiarities of natural and synthetic alpha-adrenomimetics].

The mechanical response of the isolated rat vas deferens to four alpha-adrenomimetic substances has been studied. The four test substances were noradrenaline, octopamine, 2-phenylethylamine and 2-(1-naphthylmethyl)imidazoline (Privin). Examination of the cumulative dose/response curves showed both qualitative and quantitative differences. Octopamine gave an alpha value (intrinsic activity) greater than that of noradrenaline; Privin proved to be a partial agonist but with affinity greater than that of noradrenaline. Various qualitative differences were also observed suggesting a possible explanation based on labilization of the membrane.

Adrenergic alpha-Agonists↗
PubMed1977

[Pharmacological pecularities of natural and synthetic alpha-adrenomimetic substances II].

The comparative examination of noradrenaline, octopamine, Privin and 2-phenylethylamine on the isolated rat vas deferens made under controlled conditions (1) has been extended by introducing more complex experimental conditions. Pretreatment of the animal with reserpine does not change the response to Privin, while the response to the maximal doses of noradrenaline is reduced; the response to octopamine remains unchanged while that of 2-phenyl-ethylamine is abolished.

Animals↗
PubMed1977

[Direct effect of reserpine. II. Response of the rat vas deferens to calcium].

It has been shown that reserpine competitively antagonises the response of the isolated rat vas deferens to Ca2+. It has also been shown that reserpine does not modify uptake of Ca2+ from the external medium. On the basis of the results obtained and bearing in mind the uncoupling effect of reserpine on oxidative phosphorylation, it is suggested that reserpine owes its "direct" action to reduced availability of Ca2+ for contraction due to metabolic block.

Animals↗
PubMed1977

[Selectivity of beta-adrenergic compounds. IV. Studies on 1-(4'-methylphenyl)-2-isopropylaminopropanol].

The beta-adrenergic activity of 1-(4'-methylphenyl)-2-isopropylaminopropanol (H 35/25) was studied on isolated preparations (guinea pig atria, guinea pig and calf tracheal muscle, mouse cecum). H 35/25 shows variations in both affinity and intrinsic activity at the various levels tested. The discussion shows that this cannot be used as a means of characterizing beta-adrenergic receptors.

Animals↗
PubMed1976

[Adrenergic reactivity of the gastro-intestinal tract. II. Colon of the guinea pig and cecum of the mice].

A study has been made of the alpha- and beta-adrenoreceptors in the guinea pig colon and the mouse caecum using noradrenalina as agonist and alpha- and beta-adrenolytics separately or together. In the guinea pig colon alpha-adrenolytics used alone did not alter the action of noradrenalin: one beta-lytic (propranolol) used alone has slight non dose-dependent action. The alpha-lytics used together with beta-lytic strongly potential their effect. These results are interpreted as indicating that the preparation contains alpha-receptors as well as beta-receptors; activation of the alpha-receptors is observed only when the beta-mimetic effect of noradrenalin is inhibited. In the mouse caecum alpha-lytics prove devoid of effect either alone or when associated with beta-lytics; it is deduced therefore that this preparation contains only beta-receptors.

Animals↗
PubMed1976

"Direct" effect of reserpine on various preparations.

The action of reserpine added to the bathing solution has been studied in isolated organs, examining various kinds of receptor systems and biological preparations. The investigation has been comparatively carried out in normal and reserpine-pretreated animals. The most important effect of reserpine is the inhibition of the maximum response to noradrenalin in the rat vas deferens, and the inhibition of response to furtrethonium and histamine in the intestine of rat and guinea-pig, respectively. This affect appears to be independent of the release of catecholamines, and is therefore direct, aspecific and similar to the non-competitive effect of papaverine.

Animals↗
PubMed1976

Andrenergic reactivity of the gastro-intestinal tract. I. Fundus of the rat's stomach.

The adrenergic receptors of the fundus of rat stomach are both type alpha and type beta. Activation of the alpha-adrenergic receptors gives a diphasic response in which inhibition precedes excitation. The beta-adrenergic receptors mediate exclusively inhibitory response; the beta-adrenergic component of the inhibitory response is clearly observed only when the alpha-adrenergic component is diminished. The beta-receptors can be assigned, with some reserve, to the betaalpha group.

Animals↗