Zur peripheren sympathikushemmenden Wirkung des Clonidins

Summary The influences of clonidine, tetracaine and procaine on the effects of electrical stimulation of the postganglionic sympathetic cardiac nerves have been compared in the isolated perfused rabbit heart. Much lower concentrations of clonidine than of tetracaine were necessary to antagonize the output of noradrenaline and the rise of frequency and contractility. Procaine even in the highest concentration tested did not inhibit the effects of nerve stimulation. In addition to its known central depression of sympathetic tone, clonidine exerts a specific inhibitory action on postganglionic sympathetic neurons.     

Contraction of myoepithelial cells in secreting submandibular glands of dogs

Summary In slowly secreting submandibular glands of dogs, a sympathetic effect on myoepithelial cells was demonstrated as an acceleration of the flow, follwed by retardation, on short-lasting sympathetic stimulation, particularly after -adrenoceptor-blocking drugs.Supported by grant No. 14X-00539 from the Swedish Medical Research Council     

Modulator role of prostaglandins (Pg) in adrenergic neurotransmission in carotid sinus]

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.     

Non-uniformity of regional vasomotor activity indicating the existence of 2 different systems in the sympathetic cardiovascular outflow

Summary In rabbits, 2 populations of sympathetic postganlionic fibres innervating the skin, heart, muscle and kidney could be classified by their different spike heights and their different susceptibility to noradrenaline and angiotensin amide. The ability of the 2 populations to respond to physiological stimuli in a highly differentiated manner leads to the assumption that 2 different systems in the cardiovascular sympathetic outflow exist.     

Influence of cervical sympathetic nerve stimulation on carotid sinus baroreceptor afferents

Summary In rabbits and dogs, the response of low-threshold carotid sinus baroreceptor afferent fibres to cervical sympathetic nerve stimulation at various non-pulsatile steady pressures was examined. Fibres which possessed a rhythmic bursting discharge at low pressures increased this activity during sympathetic stimulation; all other low-threshold afferents were unaffected.This work was supported by the Medical Research Council of Canada and the British Columbia Heart Foundation.     

Sympathetic, muscarinic vasodilation in cranial vessels of the cat

Pressor responses evoked by stimulation of the preganglionic sympathetic trunk of the feline superior cervical ganglion have been recorded in vivo from the vascular bed perfused by one external carotid and the vertebral artery. When vasoconstrictor activity is blocked and potential vasodilator activity enhanced by close, intracarotid injection of guanethidine and prostaglandin F2 alpha respectively, stimulation evokes a weak pressor response followed, on cessation of stimulation, by a prolonged vasodilation lasting for 6-8 min. The magnitude and duration of the poststimulation vasodilation was reduced significantly by atropine. Due to the prolonged nature of the vasodilation, it is unlikely that a sympathetic cholinergic vasodilation in the classical sense is involved.     

Role of alpha and beta adrenoceptors in the regulation of adrenergic neurotransmission in the carotid sinus]

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.     

Sympathetic preganglionic pupillodilator fibres in the light reflex

Summary The modifications of the sympathetic pupillodilator activity in the light reflex have been demonstrated by recording the electrical discharge of single preganglionic fibres in the cervical sympathetic nerve.This work was supported by a grant of CNR.     

Spontaneous thermoregulatory oscillations in cutaneous efferent sympathetic activity

Summary Patterns of changes in cutaneous efferent sympathetic activity which have previously been shown to occur during experimental manipulation of the temperature of various thermosensitive body sites, have now been shown to accompany spontaneous thermoregulatory activity. That is, under thermoneural conditions, concurrent spontaneous oscillations in skin blood flow and efferent sympathetic activity were observed.     

Coxsackievirus B4 infection of spinal sympathetic ganglion

Summary Coxsackievirus B₄ infection of a spinal sympathetic ganglion of a squirrel monkey is described. Chromatolysis and neuronophagia were extensive. It is suggested that such viral sympathetic ganglial infections may be responsible for dysfunction of organ systems.Supported by the Cardiovascular Research Fund, the Rowell A. Billups Fund for Research in Heart Disease, the Feazel Laboratory and grant No. RR-00164-17 from the Animal Resources Branch, Division of Research Resources of NIH.     

Brown adipose tissue activity in hypophysectomized rats: involvement of sympathetic system

At thermal neutrality, hypophysectomy enhanced interscapular brown adipose tissue (IBAT) activity (increase of purine nucleotide binding) in the rat. This stimulation is dependent on sympathetic system integrity since surgical denervation of IBAT impairs its thermogenic response.     

Brown adipose tissue activity in hypophysectomized rats: involvement of sympathetic system

Summary At thermal neutrality, hypophysectomy enhanced interscapular brown adipose tissue (IBAT) activity (increase of purine nucleotide binding) in the rat. This stimulation is dependent on sympathetic system integrity since surgical denervation of IBAT imparis its thermogenic response.     

Zentrale vegetative LSD-Effekte

Summary d-Lysergic acid diethylamide (LSD 25) produces in rabbits a syndrome consisting of hyperthermia, hyperglycemia, mydriasis, pilomotor activation, cardiac acceleration etc. Analysis of these effects leads to the assumption of an increased sympathetic discharge induced by the central nervous action of LSD 25. Comparison of LSD 25 and reserpine shows opposite characteristics of these two drugs not only in the field of vegetative pharmacology but also concerning influence on psychic functions in man. The possibility should, therefore, be considered that an increased excitatory state of sympathetic centres by LSD 25 is a main factor in the pathogenesis of the well-known psychic disturbances produced by this amide in man.     

Sympathetic,muscarinic vasodilation in cranial vessels of the cat

Summary Pressor responses evoked by stimulation of the preganglionic sympathetic trunk of the feline superior cervical ganglion have been recorded in vivo from the vascular bed perfused by one external carotid and the vertebral artery. When vasoconstrictor activity is blocked and potential vasodilator activity enhanced by close, intracarotid injection of guanethidine and prostaglandin F₂ respectively, stimulation evokes a weak pressor response followed, on cessation of stimulation, by a prolonged vasodilation lasting for 6–8 min. The magnitude and duration of the poststimulation vasodilation was reduced significantly by atropine. Due to the prolonged nature of the vasodilation, it is unlikely that a sympathetic cholinergic vasodilation in the classical sense is involved.     

Acute stress reduces the sensitivity of the vasculature to sympathetic control

Vascular smooth muscle from rabbits subjected to acute severe stress exhibits decreased sensitivity to sympathetic regulation. Stimulation of the sympathetic innervation of isolated vascular segments resulted in a similar subsensitivity as did exposure to norepinephrine (NE) but not histamine. Periodic contraction of these segments caused an increase in their maximum ability to contract independent of the constrictor procedure used. These results suggest that the increase in sympathetically mediated NE release that occurs in stress and some other pathological conditions may result in a blunting of neural control and possibly resistance to certain therapeutic agents.     

Inhibition of noradrenaline release from sympathetic nerves by pentobarbital

Pentobarbital concentrations of 10--100 micrometer selectively inhibited the noradrenaline release evoked by activation of the nicotinic receptors on the terminals sympathetic nerves of the rabbit heart. Higher concentrations also decreased the noradrenaline release induced by KCl or by electrical stimulation of the nerve axons.     

Sympatho-inhibitory mechanisms acting at sympathetic ganglia to attenuate hypothalamic-induced pressor effect in the cat

Summary Pressor and tachycardic effects induced in the cat by stimulation of a lateral hypothalamic (LH) site, are shown to be mediated by sympathetic ganglia nicotinic receptor, and potentiated under atropine methyl nitrate sympathetic ganglia blockage. It is postulated that a sympatho-inhibitory pathway muscarinic ganglionic mechanism, co-activated by the LH stimulation, attenuates the pressor and tachycardic effects, the potentiation presumably being a manifestation of blockage of that mechanism.     

Sympatho-inhibitory mechanisms acting at sympathetic ganglia to attenuate hypothalamic-induced pressor effect in the cat

Pressor and tachycardic effects induced in the cat by stimulation of a lateral hypothalamic (LH) site, are shown to be mediated by sympathetic ganglia nicotinic receptor, and potentiated under atropine methyl nitrate sympathetic ganglia blockage. It is postulated that a sympatho-inhibitory pathway muscarinic ganglionic mechanism, co-activated by the LH stimulation, attenuates the pressor and tachycardic effects, the potentiation presumably being a manifestation of blockage of that mechanism.     

Intracerebroventricular angiotensin II increases arterial blood pressure in rhesus monkeys by stimulation of pituitary hormones and the sympathetic nervous system

Summary Intracerebroventricular injections of angiotensin II in anesthetized rhesus monkeys increase systemic blood pressure and heart rate. These effects are accompanied by an increase in plasma ADH, cortisol, adrenaline and noradrenaline. Angiotensin II may participate in central mechanisms of blood pressure regulation by its stimulatory effect on the sympathetic nervous system, on ADH and on ACTH release in primates.     

Modifications ultrastructurelles provoquées par quelques médicaments sur les terminaisons nerveuses adrénergiques et sur la médullaire surrénale

Summary It has been shown that reserpine and guanethidine deplete granules containing catecholamine in sympathetic nerve endings of both the pineal gland and the vas deferens. This effect is blocked by iproniazid. Bretylium is not able to deplete these granules but it modifies their aspect. It has also been observed that granules of the adrenal medulla are depleted less easily than those of sympathetic nerve endings.