ABSTRACT
In the isolated Rabbit heart, high pressure, on the one hand, inhibits the noradrenaline release, and on the other hand, induces both the biosynthesis and release of PGs(PGE2,PGF2 alpha) from the auricles and mainly from the right auricle i.e. where the sympathetic nerve endings are the most numerous. Therefore, high pressure, by a negative feedback process, plays a great part in moderating the adrenergic neurotransmission responsible for the hypertension. These effects result from a supplementary pressure which acts on the walls of coronary arteries and arterioles and modifies their distensibility. It thus appears that in the walls of arteries and arterioles there are baroreceptors which are sensitive to the pressure variations in order to regulate adrenergic neurotransmission, by means of a reflex path still unknown.
Subject(s)
Heart/physiology , Pressoreceptors/physiology , Prostaglandins/metabolism , Sympathetic Nervous System/physiology , Animals , Heart/innervation , In Vitro Techniques , Myocardium/metabolism , Pressure , Prostaglandins/biosynthesis , Rabbits , Synaptic TransmissionSubject(s)
Muscle Contraction/drug effects , Muscle, Smooth/physiology , Phenethylamines/pharmacology , Prostaglandins/pharmacology , Thromboxane A2/pharmacology , Thromboxanes/pharmacology , Animals , Arachidonic Acids/metabolism , Cattle , Lung/metabolism , Male , Microsomes/metabolism , Muscle, Smooth/drug effects , Prostaglandins/biosynthesis , Rabbits , Rats , Seminal Vesicles/metabolism , Thromboxane A2/biosynthesisABSTRACT
The soluble and microsomal fractions of Rabbit myocardium are not able to induce the synthesis of thromboxanes. On the contrary, they inhibit the thromboxane synthetase of various sources. The chemical structure of the active constituent responsible for this activity is not yet known: it is probably neither of an enzymatic nature, nor a protein of high molecular weight.
Subject(s)
Heart/physiology , Microsomes/physiology , Oxidoreductases/metabolism , Thromboxane-A Synthase/metabolism , Tissue Extracts/pharmacology , Animals , Arachidonic Acids/metabolism , Arteries/metabolism , Cattle , Rabbits , Thromboxane A2/biosynthesisABSTRACT
In Rabbit carotid sinus, the presence of sympathetic nerve endings capable of releasing noradrenaline has been demonstrated. The release of NA in response to sympathetic nerve stimulation was decreased by PgE2 and a precursor of Pg (arachidonic acid) but was strongly increased by an inhibitor of Pg biosynthesis (indomethacin). The experiments carried out demonstrated that freshly synthesized Pg acts in the same way as exogenous Pg and suggested that Pg could have a regulating effect on adrenergic neurotransmission in carotid sinus. The role of this regulating mechanism in the physiology of carotid sinus has been discussed.
Subject(s)
Carotid Sinus/physiology , Prostaglandins/physiology , Synaptic Transmission , Animals , Arachidonic Acids/pharmacology , Dose-Response Relationship, Drug , Indomethacin/pharmacology , Norepinephrine/metabolism , Prostaglandins/biosynthesis , Prostaglandins E/pharmacology , Rabbits , Synaptic Transmission/drug effectsABSTRACT
The experiments carried out showed the presence- in sympathetic nerve endings ot the carotid sinus- of alpha and beta adrenoceptors which by means of respective negative and positive feedback processes, modulated NA release induced by a sympathetic nerve stimulation. Similarly, Pgs acted by means of a negative feedback mechanism to regulated adrenergic neuro-transmission in carotid sinus but they could not be considered as the chemical mediators of either alpha or beta adrenoceptors.
Subject(s)
Carotid Sinus/physiology , Receptors, Adrenergic, alpha/physiology , Receptors, Adrenergic, beta/physiology , Receptors, Adrenergic/physiology , Animals , Carotid Sinus/drug effects , Carotid Sinus/innervation , Electric Stimulation , Feedback , Norepinephrine/metabolism , Norepinephrine/pharmacology , Phentolamine/pharmacology , Rabbits , Receptors, Adrenergic, alpha/drug effects , Receptors, Adrenergic, beta/drug effectsABSTRACT
The experiments carried out on the isolated carotid sinus in the rabbit demonstrated that alpha and beta adrenoceptors are capable of detecting the circulating catecholamines and the catecholamines of the synaptic cleft in order to modulate the release of noradrenaline from the sympathetic nerve endings in response to a potential action.
Subject(s)
Carotid Sinus/physiology , Norepinephrine/metabolism , Receptors, Adrenergic, alpha/physiology , Receptors, Adrenergic, beta/physiology , Receptors, Adrenergic/physiology , Synapses/physiology , Animals , Carotid Sinus/drug effects , Electric Stimulation , Isoproterenol/pharmacology , Phentolamine/pharmacology , Propranolol/pharmacology , Rabbits , Receptors, Adrenergic, alpha/drug effects , Receptors, Adrenergic, beta/drug effectsABSTRACT
In isolated perfused rabbit heart, Pg E2 at concentrations ranging from 1.10(-8) to 1.10(-4) M has shown no significant action either on the biosynthesis or on the metabolism of NA. But it inhibited NA uptake, nevertheless this action was weak.
Subject(s)
Heart/drug effects , Norepinephrine/metabolism , Prostaglandins E/pharmacology , Animals , Biological Transport/drug effects , Myocardium/metabolism , Norepinephrine/biosynthesis , Perfusion , Rabbits , Sympathetic Nervous System/physiologyABSTRACT
In the anaesthetized Dog, synthetic substance P in one dose (0.5 mug/kg i.v.) induced a quick hypotensive but short-lasting action and a respiratory analeptic activity which only appeared with some delay and lasted more than one hour. The possibility of a rapid metabolization of synthetic SP is discussed.
Subject(s)
Hemodynamics/drug effects , Respiration/drug effects , Substance P/pharmacology , Animals , Blood Pressure/drug effects , Carbon Dioxide , Cardiac Output/drug effects , Dogs , Female , Heart Rate/drug effects , Injections, Intravenous , Male , Oxygen , Substance P/metabolism , Time Factors , Vascular Resistance/drug effectsABSTRACT
Influence of the inhibiting action of PgE2 on the captation of NA by isolated Rabbit heart at a concentration of 1 X 10(-4)M, although its action on extraneuronal captation is already apparent at 1 X 10(-8)M.
Subject(s)
Myocardium/metabolism , Norepinephrine/metabolism , Prostaglandins E/pharmacology , Animals , Dose-Response Relationship, Drug , Heart/innervation , In Vitro Techniques , RabbitsABSTRACT
A series of pyrazoline derivatives was synthetised and evaluated for toxicological and pharmacological effects; analgesic, hypnotic, anti-inflammatory, antipyretic and cardiovascular properties were screened. Tested compounds were found to have a low toxicity; one of them showed a good analgesic activity without side effects.
