Matao Sakanashi

Activation of afferent cardiac sympathetic nerve fibers of the cat by pain producing substances and by noxious heat

SummaryAfferent discharges of 64 single units were recorded from the left cardiac sympathetic nerve of anesthetized cats. Mechano-sensitive terminals of the afferent fibers were localized in the extrapulmonary part of the pulmonary artery, left atrium, left ventricle and left pericardium, as determined by direct mechanical probing of the heart after death of the animals. Conduction velocity of the fibers ranged from 2.5 to 14.6 m/s. Excitation of these Aδ-fibers with mechanically excitable endings was produced by intravenous injections of acetylcholine, 5-hydroxytryptamine, bradykinin, histamine and veratridine, and/or by topical application of these agents to the receptor region. Noxious heat to the mechanically excitable field in the wall of the pulmonary artery and the left ventricle also activated their afferent fibers. These observations provide evidence for a certain number of afferent units in the cardiac sympathetic nerve with polymodal sensitivity. These afferent fibers can provide the spinal cord with information not only on mechanical changes in cardiac events, but also changes in the chemical environment of the cardiac nerve ending, possibly produced by myocardial ischemia.

High-energy phosphate metabolism of isolated coronary arteries in the dog.

The correlation between phosphate metabolism and isometric contraction was investigated in helical strips from dog coronary artery. Adenosine triphosphate (ATP) and creatine phosphate (CP) contents of resting strips did not significantly change during anoxia. ATP content remained unchanged during potassium-contracture under aerobic conditions but was significantly reduced by anoxia. Pretreatment with iodoacetate resulted in a striking reduction in ATP content with a less marked decrease in CP content. ATP-depleting effect of iodoacetate was reduced slightly by the addition of pyruvate, but contractile response was not restored. It is considered that high-energy phosphates provided by anaerobic glycolysis can meet the energy requirements of resting coronary vessels but are insufficient for maintaining active tension. In resting strips equilibrated for 2 h in oxygenated bath solution, the reactivity to KCl and anoxia appears to be dependent on the availability of ATP.

Dopaminergic Receptors in the Coronary Arteries

ABSTRACT The purpose of the present study was to analyse the mechanisms of action of dopamine on the coronary circulation. Dopamine increased coronary blood flow in anesthetized dogs. The increase was not abolished by propranolol but enhanced by phentolamine. The dopamine-induced coronary vasodilatation under alpha and beta adrenoceptor blockade was significantly attenuated by haloperidol which did not affect the coronary vasodilator action of acetylcholine, adenosine and papaverine. When treated with indomethacin after both alpha and beta blockade the dopamine-induced increase in coronary blood flow was strongly inhibited. It was considered that dopamine stimulated alpha and beta adrenoceptors, and specific receptors as well in the coronary arteries. A possible involvement of prostaglandin El in the regulation of coronary circulation was also suggested.

Effects of dihydroergotamine methanesulfonate on the microcirculation of the rat cremaster muscle

SummaryEffects of dihydroergotamine on the microcirculation of the rat cremaster muscle were investigated microscopically using colour photographic technique. 1.Dihydroergotamine 10−4 g/ml constricted arterioles of the rat cremaster.2.Dihydroergotamine 10−4 g/ml produced a significant contraction of venules.3.Dihydroergotamine 10−4 g/ml markedly inhibited the contractile response of noradrenaline 10−6 g/ml on arterioles of the rat cremaster. The results suggest that dihydroergotamine has an appreciable vasoconstrictive action, especially upon venules, and that dihydroergotamine also has an adrenergic alpha-receptor blocking action.By means of highly sensitive negative colour film we obtained a satisfactory photograph of the rat cremasters circulation.