Electrical Stimulation Of Preganglionic Fibres Research Articles

Synaptic and antidromic potentials of visceral neurones in ganglia of the lumbar sympathetic chain of the cat.

Intracellular recordings were obtained in vitro from two hundred and twenty post-ganglionic neurones of the fourth and fifth lumbar paravertebral ganglia of cats. Thirty-seven percent of neurones tested evoked antidromic responses during electrical stimulation of post-ganglionic fibres in the inferior lumbar splanchnic nerves. Twenty-seven percent of neurones tested evoked antidromic responses during electrical stimulation of post-ganglionic fibres in the lumbar sympathetic chain. Twenty-four percent of neurones tested evoked convergent antidromic responses during electrical stimulation of post-ganglionic fibres in separate inferior lumbar splanchnic nerves or lumbar sympathetic chain, and by inferior lumbar splanchnic nerves and lumbar sympathetic chain. Eighty-six percent of paravertebral post-ganglionic fibres which project to the inferior lumbar splanchnic nerves or lumbar sympathetic chain were composed of B fibres with maximal conduction velocities ranging from above 2.0 to 16.0 m/s. Fourteen percent of post-ganglionic fibres were composed of C fibres with maximal conduction velocities ranging from 0.2 to 2.0 m/s. Synaptic responses of neurones were recorded intracellularly during electrical stimulation of preganglionic fibres in inferior lumbar splanchnic nerves, lumbar white rami communicantes and lumbar sympathetic chain located one to three segments above the fourth and fifth lumbar ganglia and one to two segments below. Synaptic responses consisting of excitatory post-synaptic potentials and action potentials were mediated via nicotinic receptors. Twenty-seven percent of neurones tested received synaptic input from only one or two segments of the lumbar sympathetic chain. Seventy-three percent of neurones tested received convergent synaptic input from one or two segments of the lumbar sympathetic chain, lumbar white rami communicantes and inferior lumbar splanchnic nerves. It is concluded that central preganglionic fibres which project to inferior lumbar splanchnic nerves also project to the lumbar sympathetic chain to innervate neurones in the L4 and L5 ganglia. Synaptic responses of neurones during electrical stimulation of preganglionic fibres in the lumbar sympathetic chain and in the inferior lumbar splanchnic nerves were reduced in a chronic isolated segment of the sympathetic chain devoid of central preganglionic inputs. It is concluded that synaptic responses elicited in neurones during electrical stimulation of inferior lumbar splanchnic nerves and lumbar sympathetic chain were mediated in part via collaterals of central preganglionic axons and in part via axons whose cell bodies were located in the periphery.(ABSTRACT TRUNCATED AT 400 WORDS)

Central innervation of neurones in the inferior mesenteric ganglion and of the large intestine of the cat.

1. Segmental, lumbar sympathetic outflow to neurones in the cat inferior mesenteric ganglion and to the large intestine were studied. Synaptic responses of neurones in the inferior mesenteric ganglion were recorded intracellularly, in vitro, during electrical stimulation of preganglionic fibres in the lumbar white rami. Synaptic responses consisted of excitatory post-synaptic potentials and/or action potentials.2. None of the neurones tested received synaptic input from spinal cord segment L(1). There was synaptic input from segments L(2)-L(5) of the spinal cord. The strongest synaptic input arose from spinal cord segments L(3) and L(4).3. 42% of the neurones tested received synaptic input from only one spinal cord segment. 54% of the neurones tested received convergent synaptic input from two, three or four adjacent lumbar segments.4. Electrophysiological measurements indicated that the number of preganglionic fibres in any lumbar white ramus communicans which provided synaptic input ranged from one to thirteen. Each lumbar white ramus contained, on average, five preganglionic fibres which provided synaptic input to neurones in the inferior mesenteric ganglion.5. Changes in intraluminal colonic pressure were measured in vivo during electrical stimulation of preganglionic fibres in the different lumbar white rami and lumbar ventral roots. Electrical stimulation of white rami L(3) and L(4) abolished phasic changes in intraluminal colonic pressure and reduced basal pressure to near zero. Electrical stimulation of preganglionic fibres in lumbar ventral roots L(3) and L(4) abolished phasic changes in intraluminal colonic pressure and reduced basal pressure to near zero. Stimulation of ventral roots L(1), L(2) and L(5) had little to no effect on intraluminal pressure.6. Based on the data obtained in this study, two hypotheses are proposed. First, spinal cord segments L(3), L(4) and L(5) are the primary sources of central synaptic input to neurones in the inferior mesenteric ganglion. Secondly, spinal cord segments L(3) and L(4) control colonic motility.

Mechanism of cardiovascular action of Terminalia arjuna.

TERMINALIA ARJUNA (Hindi name Arjuna, Family Combretacae) has been used in the treatment of cardiovascular disorders by Ayurvedic physicians. However, its properties have not been scientifically evaluated so far. Therefore, the present study was carried out to examine the underlying mechanism of the cardiovascular effects of aqueous solution of TERMINALIA ARJUNA extract. Intravenous (I. V.) administration of the extract was found to induce dose dependent decrease in blood pressure (B. P.) and heart rate (H. R.). These extracts also inhibited carotid occlusion response, without affecting the pressor responses, induced by intravenous injection of norepinephrine and by electrical stimulation of preganglionic fibres of the abdominal splanchnic nerve. Hypotension and bradycardia were also observed following the injection of the extract into the lateral cerebral ventricle and vertebral artery. The results of the present study show that the hypotensive and bradycardiac effects of T. ARJUNA are mainly of central origin.

Some cardiovascular effects of germine-3-monoacetate

In anesthetized dogs germine-3-monoacetate (GMA), 40 to 640 μg/kg i.v., increased mean arterial pressure, right ventricular contractile force, left ventricular pressure and left ventricular dp/dt max. At 160 μg/kg i.v., GMA slightly increased the heart rate. The positive inotropic effect of GMA was not prevented by denervation of the carotid sinuses, pithing of the spinal cord, or adrenalectomy; it was blocked or greatly reduced by propranolol, sotalol, reserpine, mecamylamine or tetrodotoxin. When administered to the superior cervical ganglion of cats GMA enhanced contractions of nictitating membrane caused by electrical stimulation of preganglionic fibers with single electrical stimuli. At 6 to 100 μg/ml GMA had dose dependent positive inotropic and chronotropic effects on the isolated guinea pig atria. The in vivo effects of GMA were apparently mediated by the sympathetic nervous system; in addition, at high concentrations, GMA had a direct cardiotonic action on the artrial muscle.