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Central vagal sensory and motor connections: human embryonic and fetal development.

The embryonic and fetal development of the nuclear components and pathways of vagal sensorimotor circuits in the human has been studied using Nissl staining and carbocyanine dye tracing techniques. Eight fetal brains ranging from 8 to 28 weeks of development had DiI (1,1'-dioctadecyl-3,3,3',3' tetramethylindocarbocyanine perchlorate) inserted into either the thoracic vagus nerve at the level of the sternal angle (two specimens of 8 and 9 weeks of gestation) or into vagal rootlets at the surface of the medulla (at all other ages), while a further five were used for study of cytoarchitectural development. The first central labeling resulting from peripheral application of DiI to the thoracic vagus nerve was seen at 8 weeks. By 9 weeks, labeled bipolar cells at the ventricular surface around the sulcus limitans (sl) were seen after DiI application to the thoracic vagus nerve. Subnuclear organization as revealed by both Nissl staining and carbocyanine dye tracing was found to be advanced at a relatively early fetal age, with afferent segregation in the medial Sol apparent at 13 weeks and subnuclear organization of efferent magnocellular divisions of dorsal motor nucleus of vagus nerve noticeable at the same stage. The results of the present study also confirm that vagal afferents are distributed to the dorsomedial subnuclei of the human nucleus of the solitary tract, with particular concentrations of afferent axons in the gelatinosus subnucleus. These vagal afferents appeared to have a restricted zone of termination from quite early in development (13 weeks) suggesting that there is no initial exuberance in the termination field of vagal afferents in the developing human nucleus of the solitary tract. On the other hand, the first suggestion of afferents invading 10N from the medial Sol was not seen until 20 weeks and was not well developed until 24 weeks, suggesting that direct monosynaptic connections between the sensory and effector components of the vagal sensorimotor complex do not develop until this age.

Carbocyanines↗

The influence of bulbospinal monoaminergic pathways on sympathetic nerve activity.

1. Spontaneous and reflex activity was recorded from renal and splanchnic nerves and thoracic white rami during discrete electrical stimulation within the medulla oblongata of anaesthetized cats.2. Inhibition or excitation of spontaneous sympathetic nerve activity was obtained from several medullary regions.3. The long-circuited reflex elicited in renal nerves and the spinally mediated reflex discharge produced in white rami by single shock stimulation of intercostal nerves were inhibited by stimulation within the sympatho-inhibitory areas of the medulla.4. Activation of spontaneous sympathetic nerve activity or inhibition of spontaneous and reflex sympathetic nerve activity was obtained during electrical stimulation within the lateral funiculi of the cervical spinal cord in unanaesthetized decerebrate cats, spinalized at C1.5. There was a correlation between the position of some sympatho-inhibitory regions of the medulla and spinal cord and the position of the cell bodies and axons of descending monoamine-containing neurones.6. Intravenous administration of the precursor of noradrenaline, L-DOPA, to unanaesthetized decerebrate cats, spinalized at C1, was followed by a depression of spontaneous activity in renal nerves and reflex responses elicited in renal nerves and white rami.7. Similarly the precursor of 5-hydroxytryptamine, 5-HTP, caused a depression of reflex activity elicited in renal nerves and white rami, but had no effect on spontaneous renal nerve activity.8. It is suggested that there exist both noradrenergic and tryptaminergic pathways which descend to the spinal cord from the medulla and which are inhibitory to sympathetic outflow.

5-Hydroxytryptophan↗

Vagal innervation of the gastrointestinal tract arises from dorsal motor nucleus while that of the heart largely from nucleus ambiguus in the cat.

The origin of medullary cells that form the cardiac vagal branch and the vagal branches in the lower thorax innervating the gastrointestinal (GI) tract was studied using horseradish peroxidase (HRP), a retrograde transport tracer in the cat. The distributions of parasympathetic postganglionic neurons of the heart were studied with acetylcholinesterase histochemistry. Intracardiac ganglionic neurons were found mainly in the connective tissue surrounding the base of the pulmonary arteries and in an area in and dorsal to the interatrial septum. Following injection of HRP into the subepicardum where most of the cardiac postganglionic neurons reside, 91% of the labelled neurons were found bilaterally distributed in the nucleus ambiguus (NA). A small population of labelled neurons was found in the dorsal motor nucleus of the vagus (DMV) and an intermediate zone (IZ) between the two nuclei. When HRP was injected into the left or right cardiopulmonary vagus branch, labelled neurons were found exclusively in the ipsilateral NA, DMV and IZ with a predominance in the NA. In the thorax, after they course around the heart, the left and right thoracic vagus nerves divides into a left and a right branch, respectively. The left branch of the left thoracic vagus joins the left branch of the right thoracic vagus to form the anterior vagus nerve at 3 cm above the diaphragm. The right branch of the right thoracic vagus nerve joins the right branch of the left thoracic vagus to form the posterior vagus nerve. After application of HRP into the right or the left branch of the left thoracic vagus, HRP labelled cells were found in the left DMV. Similarly, after application of HRP into the left or the right branch of the right thoracic vagus, labelled cells were found in the right DMV. On the other hand, when HRP was injected into the anterior vagus, labelled neurons were found bilaterally in the DMV. This suggests that all rostral branches of the thoracic vagus have their origin in the ipsilateral DMV, and intermixing occurs only at the caudal level near the diaphragm. Findings of the present experiments suggest that parasympathetic preganglionic neurons innervating the GI tract are located exclusively in the DMV while those of the heart are located mainly in the NA. Within the DMV, GI vagal neurons were found medially from the level 0-2.5 mm rostral to the obex. In contrast, cardiac vagal neurons were found in the lateral edge of the DMV at the level 0-1 mm rostral to the obex.

Animals↗

Organization of forelimb motoneuron pools in two bat species (Eptesicus fuscus and Myotis lucifugus).

The present investigation provides further evidence of the conservation of motor nuclei in amniotes. The position of six forelimb and shoulder motor pools were mapped in two species of bat, Eptesicus fuscus and Myotis lucifugus. The intraspinal locations of motor pools were revealed by labeling with the retrograde neuronal tracer WGA-HRP injected into the bellies of six muscles: m. pectoralis, m. spinodeltoideus, mm. triceps brachii (long and lateral heads), m. infraspinatus, m. supraspinatus, and m. biceps brachii. The positions of the labeled motor pools were reconstructed from serial transverse and horizontal sections of the spinal cord. WGA-HRP-labeled cells were located midway between cervical spinal nerves four and five to midway between cervical spinal nerve eight and the first thoracic spinal nerve. Individual motor pools formed fusiform clusters of cells with little intermingling of neurons between adjacent motor pools. The pectoralis motor pool contained significantly more motoneurons than all other motor pools for M. lucifugus. The pectoralis pool in E. fuscus contained more motoneurons than the biceps, supraspinatus, and infraspinatus, but not the spinodeltoid or the triceps brachii. The biceps, spinodeltoid, infraspinatus and supraspinatus pools were located rostrally; the pectoralis and triceps pools caudally. The pectoralis pool was the most medial and the spinodeltoid pool was the most lateral. These data suggest that the locations of shoulder and forelimb motor pools are ontogenetically and phylogenetically conserved across tetrapods and independent of the function of the muscles in adults.

Animals↗

Double-crush nerve compression in thoracic-outlet syndrome.

We studied 165 cases of thoracic-outlet syndrome in 142 patients in whom resection of the first rib had been performed. In seventy-three cases (44 per cent), there was compression of a nerve distally, as shown by electromyography and conduction studies. The most common secondary compression was carpal tunnel syndrome (forty-one cases). Thirteen patients needed an operation at three sites or more. Our results show that proximal compression of a nerve lessens its ability to withstand more distal compression. Once the diagnosis of thoracic-outlet syndrome has been made, the possibility of an additional distal compression neuropathy should be investigated.

Adolescent↗

Recurrent laryngeal nerve paralysis associated with thoracic aortic aneurysm.

The association of vocal cord dysfunction with thoracic aortic aneurysm (TAA) has been noted in the cardiovascular and otolaryngologic literature. A retrospective review of 168 cases of TAA was performed in order to: (1) define the natural history of associated recurrent laryngeal nerve paralysis (RLNP) and (2) propose mechanisms for the development of RLNP in operated and nonoperated aneurysms. Of 168 aneurysms, 5% manifested hoarseness secondary to RLNP. All had type I aneurysms. Only one patient regained vocal cord function after surgical treatment of the aneurysm. RLNP developed as a sequela of TAA repair in 12% of the patients managed surgically. RLNP associated with TAA type III repair had a higher incidence of recovery than paralysis that occurred after TAA type I repair (40% vs. 0% recovery). Sixty-six percent of all patients with permanently paralyzed larynges in this series attained glottic competence sufficient to avoid Teflon injection, and 27% of all RLNP associated with TAA in this series required Teflon injection for aspiration, severe dysphonia, or both. Seventeen percent of the patients with vocal cord paralysis associated with TAA recovered within 12 months. Aneurysm classification and pertinent anatomic relationships are discussed with reference to various mechanisms of recurrent laryngeal nerve paralysis.

Aged↗

Treatment of intercostal neuralgia with 10 per cent ammonium sulfate.

Intercostal nerves were injected with 10 per cent annomium sulfate in 41 patients (52 total sets of injections) for management of intercostal neuralgia from radical mastectomy (six blocks), thoracotomy (20 blocks), or unknown etiology (26 blocks). Five patients failed to return for follow-up evaluation and could not be located. Sixty per cent (28/47) of the treatments produced complete or nearly complete (excellent) relief of pain. Excellent pain relief persisted for more than 20 days after 22 treatments and for more than 90 days after seven treatments. Postblock neuritis never occurred. We conclude that intercostal nerve block with 10 per cent ammonium sulfate effectively relieves intercostal neuralgia and is not associated with postblock neuritis. We therefore believe that ammonium sulfate nerve blocks should be administered for treatment of intercostal neuralgia before phenol or alcohol nerve blocks or a surgical procedure.

Ammonium Sulfate↗

Diabetic truncal polyneuropathy.

Diabetic truncal polyneuropathy is a clinical entity characterized by sensory deficit in the distribution of the thoracic intercostal nerves. The sensory loss is relatively symmetric and involves multiple thoracic dermatomes, beginning close to the anterior midline. Diabetic truncal polyneuropathy occurs in patients with advanced distal polyneuropathy involving the limbs. This entity is important because it can be confused with myelopathies that produce sensory levels over the torso. Moreover, recognition of diabetic truncal polyneuropathy is important since this disorder is associated with autonomic neuropathy.

Adult↗

The cite of action of nerves in the pulmonary vascular bed in the dog.

1. The effects of stimulation of the thoracic vagosympathetic nerve or upper thoracic sympathetic chain on the pulmonary vascular resistance have been studied in atropinized, isolated, ventilated lung lobes under various conditions of pulmonary circulation perfusion. Throughout the nerve-stimulation tests bronchial circulation perfusion was maintained or temporarily interrupted.2. The pulmonary vascular resistance increase evoked by nerve stimulation (a) occurred in the absence of tidal air changes; (b) did not consistently differ during predominantly ;sluice' and ;non-sluice' conditions of pulmonary circulation perfusion; (c) was approximately one and a half times greater during constant pressure than during constant volume inflow perfusion of the pulmonary circulation; and (d) was greater during reverse than during forward perfusion.3. In lung lobes perfused in either direction at constant volume inflow nerve stimulation produced an increase in inflow pressure and a diminution in total lung blood volume reflected by a temporary increase in blood outflow.4. In lung lobes in which neither the pulmonary nor the bronchial circulations were perfused and the capillaries were completely blocked by high intratracheal pressures, thus isolating the pulmonary arterial system from the venous system, nerve stimulation produced a diminution in the blood volume of both systems.5. Nerve stimulation produced a rise in bronchial arterial pressure in the absence of pulmonary circulation perfusion.6. Further evidence is adduced that pulmonary vasomotor nerve responses do not depend upon the transfer of transmitter substances from the bronchial to the pulmonary circulation.7. The possible significance of these observations in relation to the site of action of pulmonary vasomotor nerves is discussed.

Animals↗