The influence of the pelvic nerves on. anorectal motility in the cat

The influence of the parasympathetic pelvic nerves on anorectal motility was studied in anaesthetized cats. Anal pressure and rectal motility were recorded by a manometric and a volumetric method, respectively. Severing of the pelvic nerves did not cause any pressure change in the anus, indicating that these nerves are not significantly tonically active. Efferent low intensity (0.05–0.5 ms, 8 V at 5 Hz) electrical stimulation of the pelvic nerves (PNS) elicited a contraction of the internal anal sphincter (IAS), while high intensity stimulation (> 1 ms, 8 V at 5 Hz) caused a sphincter relaxation. A rectal contraction was noted on both low and high intensity stimulation. After sectioning of the sympathetic nerves, PNS elicited a contraction in both the anus and the rectum irrespective of stimulation intensity. PNS inhibited the anal contraction elicited by simultaneous stimulation of the sympathetic nerves or noradrenaline infusion. The inhibitory anal responses to PNS were unaffected or augmented by atropine, unaffected by propranolol and abolished by hexamethonium. The excitatory anal effects of PNS were reduced or abolished by atropine and abolished by phentolamine. The rectal contraction induced by low intensity PNS was abolished by atropine or converted to a relaxation. In half of the experiments an atropine resistant rectal contraction was observed in response to high intensity PNS. The results are consistent with a pelvic nerve influence on IAS pressure through several mechanisms, including modulation of the activity in the sympathetic nerves and activation of inhibitory non-adrenergic, non-cholinergic neurons. The pelvic nerves convey both cholinergic and non-cholinergic excitatory, as well as non-adrenergic, noncholinergic inhibitory fibres to the rectum.     

The influence of the cerebellum and peripheral somatic nerves on the activity of Deiters' cells in the cat

Summary The influence of the cerebellum on the activity of Deiters' cells has been studied by comparing the extracellularly recorded activity of single cells in decerebellate cats and in those with an intact cerebellum. The tonic inhibitory influence of the cerebellum is reflected in three ways: a smaller proportion of those cells projecting to the spinal cord is spontaneously active; fewer cells are found which do not project to the spinal cord, indicating that activity in this population of cells is depressed; among those cells that are spontaneously active, the rates of discharge are lower.In the decerebellate cat, stimulation of either ipsior contralateral limb nerves facilitates many cells, whereas in the presence of the cerebellum, peripheral stimulation evokes facilitation followed by inhibition. The inhibition is ascribed to activation by peripheral stimulation of Purkinje cells projecting to Deiters' nucleus from the cerebellum. The thresholds for facilitation and inhibition are similar but longer stimulus trains are required to evoke inhibition. Inputs from many different nerves converge upon the same cell. Among the nerves to muscles, quadriceps was the only nerve effective at stimulus strengths below the group III range.Three populations of cells are found in Deiters' nucleus: cells receiving somatic inputs but not labyrinthine inputs; cells receiving inputs from both the labyrinth and ascending somatic systems; cells activated from the labyrinth but free of somatic influences.This work was supported in part by Grants 5R01-NS-02619 and 5T01-NS-05463 from the National Institute of Neurological Diseases and Stroke, USPHS.Public Health Service Training Fellow.     

The adrenergic cardiac nerves of the cat

A fluorescence method was used for study of the adrenergic cardiac nerves of the cat. Sixteen regions of the heart were examined. The sinoatrial and atrioventricular nodes and the interatrial septum were the most richly innervated regions of the heart. There was little difference between the density of innervation in sections of atrial and ventricular portions of the myocardium. Most of the adrenergic nerves supplying the ventricles were derived from large bundles in the atrioventricular sulcus and were distributed through the subepicardial plexus. Each coronary artery was sparsely innervated in its initial elastic segment, but the vasa vasorum were well innervated. The main trunks of the coronary arteries were surrounded by plexuses composed only of preterminal axons; adrenergic vasomotor terminals were plentiful on the external surface of the muscular media of major and minor myocardial branches. Dense plexuses of adrenergic nerves were seen in both atrioventricular valves. The pulmonary valve was well innervated and contained more adrenergic nerves than the aortic valve. Perivascular plexuses and freely ending adrenergic terminals were observed in the pericardium. Small intensely fluorescent cells were grouped around small blood vessels in the interatrial septum. Most were in the vicinity of the atrioventricular node. It is suggested that these cells, under neural control may secrete catecholamines into the microcirculation of the interatrial septum. They may exert local humoral control over the atrioventricular node or the atrial parasympathetic ganglia.     

The influence of the splanchnic nerves on the external secretion, blood flow and electrical conductance of the cat pancreas

1. Electrical stimulation of the cut peripheral end of the splanchnic nerves results in a biphasic change in electrical conductance measured across the tail of the pancreas. A phase of decreased conductance is followed by a more prolonged phase of increased conductance.     

On the transmission of sacral parasympathetic nervous influence on distal colonic and rectal motility in the cat

Experiments were performed on cats anaesthetized with chloralose and treated with adrenoceptor blocking agents. Distal colonic and rectal motility were selectively recorded by a volumetric method. The effects of muscarinic and ganglionic nicotine receptor blockade on motor responses induced by graded efferent electrical pelvic nerve stimulation (PNS) were studied. Stimulation at low current strength evoked contractions in both the colon and the rectum, which were sensitive to atropine and to hexamethonium. High intensity stimulation elicited distal colonic contractions resistant to both atropine and hexamethonium. Similar excitatory responses to high strength PNS were also observed in the rectum, though not in all experiments. Stimulation at intermediate intensities evoked distal colonic and rectal relaxations which were resistant to atropine but blocked by hexamethonium. The results indicate that PNS influences colonic and rectal motility by activation of at least three discrete non-adrenergic nervous pathways: (1) low-threshold excitatory fibres involving nicotinic and muscarinic transmission, (2) high-threshold excitatory fibres with a non-muscarinic, non-nicotinic transmission mechanism, (3) inhibitory fibres with an intermediate stimulus intensity threshold, exerting their effect by a non-muscarinic mechanism involving a nicotinic step.     

The parasympathetic secretory nerves of the nose of the cat

1. A flow of watery nasal secretion can be induced in the anaesthetized cat either by electrical stimulation of the brain stem or by the simpler procedure of stimulating the cut peripheral end of the Vidian nerve. In both instances the rate of flow of secretion was dependent on the stimulation frequency. Because brain stem stimulation caused an increase in arterial blood pressure, nasal secretion was evoked in subsequent experiments by Vidian nerve stimulation.2. The application of nicotine to the sphenopalatine ganglion shows that the secretory fibres in the Vidian nerve relay in this ganglion and reach the nasal mucosa by way of the posterior nasal nerve.3. Inhibition by atropine of the secretion induced by Vidian nerve stimulation indicates that the secretory fibres are cholinergic.4. It is suggested that the induction of nasal secretion by Vidian nerve stimulation may be useful in assessing the effects of drugs on this secretion.     

The parasympathetic secretory nerves of the lacrimal gland of the cat

1. Electrical stimulation of the brain stem of the anaesthetized cat induces a secretion from the lacrimal gland.2. The secretion is abolished either by Vidian nerve section or by the application of nicotine to the sphenopalatine ganglion.3. In contrast to stimulation of the peripheral end of the cut Vidian nerve, stimulation of the central end induces lacrimal secretion.4. A new pathway is proposed in the light of the experimental findings.     

Effects of leptin on cat intestinal motility

In a previous study, we established that leptin controls food intake and immune responses by acting on intestinal vagal chemosensitive mechanoreceptors via a functional link with interleukin-1β (Il-1β). Since the control of intestinal motility is one of the main roles of the vagal afferent fibres, we investigated the effects of leptin on intestinal electromyographic (EMG) activity which reflects intestinal motility. For this purpose, the effects of locally injected leptin on small intestine spontaneous EMG activity were studied in 23 anaesthetised cats. The EMG activity was recorded using bipolar electrodes implanted in the proximal small intestine. Leptin and Il-1β (0.1, 1 and 10 μg), administered through the artery irrigating the upper part of the intestine 20 min after cholecystokinin (CCK, 10 μg, i.a .), had significant (   P < 0.001  ) excitatory effects on intestinal EMG activity. The effects of both substances were blocked by the endogenous interleukin-1β receptor antagonist (Il-1ra, 250 μg, i.a .), by atropine (250 μg, i.a .) and by vagotomy. In the absence of CCK, leptin and Il-1β had no effect on intestinal electrical activity. It can therefore be concluded that: (1) leptin is effective only after the previous intervention of CCK, (2) the enhancement of the electrical activity induced by leptin involves Il-1β receptors and the cholinergic excitatory pathway, (3) the modes whereby the leptin-induced enhancement of EMG activity occurs strongly suggest that these effects are due to a long-loop reflex involving intestinal vagal afferent fibres and the parasympathetic nervous system.