Synthesis and beta-adrenergic activity of new completely aliphatic 3-(methyleneaminoxy)propanolamine derivatives

In a previous paper, it had been found that completely aliphatic 3-(methylene aminoxy)propanolamine derivatives showed a good beta-blocking adrenergic activity directed prevalently towards beta 2-tracheal receptors. In an attempt to change the beta-adrenergic properties of these compounds from antagonist to agonist, while still retaining the beta 2-selectivity, a series of new completely aliphatic 3-(methyleneaminoxy)propanolamine derivatives were designed in which either a hydroxylic or a methoxylic group was present on the aliphatic portion linked to the oximic carbon. The synthesis of the new compounds and their beta-adrenergic activity, evaluated by means of functional tests on isolated preparations, are described and discussed; the results obtained are then rationalised on the basis of their conformational and reactivity characteristics, determined by means of theoretical methods.

Quantitative evidence for cochlear, non-neuronal norepinephrine

Endogenous norepinephrine was quantitatively measured in cochlear tissues of pigmented and nonpigmented animals by high-performance liquid chromatography and electrochemical detection. Epinephrine, dopamine and serotonin were not detected. The cochlear norepinephrine content of the pigmented animals was found to be more than double that present in corresponding albinos. Cochlear norepinephrine was only minimally depleted 48 h after surgical removal of the superior cervical ganglion. 12 h after administration of reserpine (5 mg/kg), cochlear norepinephrine was partially depleted. These results indicate that the norepinephrine located in the cochlea is probably not confined entirely to noradrenergic nerve terminals.

Conformational analogues of antihypertensive agents related to guanethidine

In an effort to clarify the conformational requirements, if any, of agents producing adrenergic neuronal blockade through mechanisms similar to guanethidine, the synthesis and pharmacological evaluation of 15 analogues of cinnamylguanidine are described. These analogues represent derivatives in which the distance between the center of the ring system and the guanidinium nitrogen atom varies from 3.9 to 6.2 A. While conformational relationships could not be defined in this study, three analogues (3, 4, and 5) were apparently more potent than guanethidine in the in vitro assay employed.

Ontogenesis of sympathetic fibers after neonatal 6-hydroxydopamine treatment in the rat

The ontogenesis of peripheral sympathetic neurones was studied in the rat following subcutaneous injections of 6-hydroxydopamine (6-OH-DA), 100 mg/kg, 1, 3, and 5 days after birth. This treatment caused severe and long-lasting depletions of noradrenaline (NA) in various peripheral organs. Thirteen months after treatment, the endogenous NA content of the submaxillary gland and the spleen was 85% lower than in age-matched control animals, 70% lower in the duodenum, 60% lower in the heart, and 25% lower in the large intestine, while the catecholamine content in the adrenal glands was totally unaffected. The adrenergic cell population of the sympathetic ganglia was greatly diminished following treatment, but a few morphologically normal cells survived. These were probably responsible for the partial growth of fibers in all organs studied.Neonatal 6-OH-DA treatment also caused marked alterations in the ontogenesis of central noradrenergic neurones. The results suggest that 6-OH-DA crosses the blood–brain barrier when administered during the first week after birth, thereby causing an important impairment of terminal fiber growth in the anterior portion of the brain and spinal cord. The cell bodies localized in the brain stem are unaffected by this treatment.Although the neonatal treatment with 6-OH-DA greatly affected the ontogenesis of both peripheral and central adrenergic fibers, it did not cause a complete and permanent sympathectomy.

A biochemical mechanism by which adrenergic mediators modify cardiac contraction

The influence of adrenergic mediators on the Mg-stimulated actomyosin ATPase of glycerinated cardiac myofibrils was analyzed. The mediators increased ATPase activity in the presence of soluble cardiac relaxing substance, but were without effect in its absence. Mechanical changes in the fibrils accompanied changes in ATPase activity. Threshold concentrations were: dl-isoproterenol = 3 x 10–8 m, l-epinephrine = 7 x 10–8 m, and l-norepinephrine = 6 x 10–7 m. Dichloroisoproterenol and dichloroepinephrine decreased ATPase activity in both the presence and absence of relaxing substance. The depressant effects of the dichloro analogs were not altered by epinephrine and isoproterenol, and could account for adrenergic "blockade" in vivo. Evidence of the specificity of myofibrillar enzyme, relaxing substance, and adrenergic stimulus is presented. Comparison of the properties of the cardiac inotropic adrenergic receptor with the properties of the soluble cardiac relaxing system suggests that the latter constitutes an intracellular site of action of adrenergic mediators in heart muscle.

An Intrinsic Adrenergic Vasodilator Mechanism in the Coronary Vascular Bed of the Dog

The question of whether the coronary blood vessels contain an intrinsic adrenergic mechanism for vasodilatation has been examined by studying the response of the coronary vessels of the dog to isoproterenol. Initially, coronary blood flow, coronary sinus P O O 2 , mean arterial pressure, and heart rate were measured continuously in anesthetized, open-chest animals. When isoproterenol, 0.1 to 0.3 µg/kg/min, was given intravenously, coronary flow and coronary sinus P O O 2 always increased in spite of tachycardia and a reduced or unchanged arterial pressure. Although this response suggested a primary vasodilating effect of isoproterenol, a vasodilatation consequent to increased myocardial activity or an extracardiac factor could not be eliminated. Accordingly, additional studies were performed in an isolated heart arrested with potassium and perfused with whole blood at constant rates of flow. Isoproterenol was given by single injections and constant infusions and always produced a decrease of perfusion pressure. These decreases could be blocked by nethalide and, as indicated by measurements of myocardial oxygen uptake and coronary venous P O O 2 , did not depend upon increased myocardial metabolism or decreased myocardial oxygenation. With injections of 0.01, 0.1, 1.0, and 10.0 µg of isoproterenol, the decreases averaged respectively 3, 8, 14, and 26% of the control pressures. It is concluded that the coronary vessels of the dog do contain an intrinsic adrenergic mechanism for vasodilatation.