Efferent fibers in the cervical sympathetic nerve influenced by light

Spontaneous electrical activity of single-fiber preparations isolated from the central stump of the cervical sympathetic nerve has been recorded, the discharge frequency of which was greatly modified by changing the intensity of light reaching the cat's eyes. These fibers showed the highest firing frequency during darkness and the lowest in light (sometimes complete inhibition) and a gradation of the response intermediate illumination values. Light stimulations ranged from 0 to 1500 lux. The close correlation between the discharge frequency of these fibers and at the light stimulus intensity suggested that the fibers originated from the Budge's ciliospinal center and were directed to the dilatator pupillae muscle.Analysis of these units, besides confirming the intervention of the sympathetic system in the development of the pupillary light reflex, corroborates the hypothesis of a larger participation of sympathetic nerves in the reflex response to darkness than in the response to light. The role of sympathetic nerves in the direct light reflex appeared larger than in the consensual one. The conduction velocities of the light-responsive components were in a range of 6 to 25 m/sec (usually between 10 and 15 m/sec) as determined by (i) the action potential evoked in the single-fiber preparations, (ii) the functional analysis of compound action potentials, and (iii) the use of the antidromic occlusion method on the whole cervical sympathetic nerve. Very small doses of Nembutal (5 mg/kg) greatly decreased the resting discharge of the sympathetic light-responsive fibers and completely abolished the response to darkness.     

Tonic sympathetic activity in the sciatic nerve of the rabbit

Spontaneous sympathetic activity of tibial and peroneal nerves was investigated in anaesthetized rabbits using the multichannel coherent recording technique. The tonic activity of these fibres is shown to be mainly irregular. Sometimes it correlates with the cardiac rhythm. No modulation with 10 c/s frequency described by other researchers and no respiratory modulation are observed. At constant arterial pressure the amplitude of irregular changes in the nerve activity exceeded several times the average level of the activity.     

The periodic components of the integral tonic activity of the sympathetic nerves

Sympathetic spontaneous activity in peripheral nerves of limbs and activity of C-fibres of the cervical sympathetic nerve trunk (CSNT) were recorded in situ from anaesthetized rabbits using multichannel coherent recording technique. Spectral characteristics of the activity and correlation between nerve activity and blood pressure were estimated. The data obtained have suggested that C-fibres in the CSNT are mainly vasoconstrictor fibres and their activity is more baroreceptor-dependent than that of sympathetic fibres in peripheral nerves. It is found that latencies of changes in the arterial blood pressure in response to changes in sympathetic activity are between 4 and 10 s.     

Effect of pentobarbital anesthesia on renal sympathetic nerve activity in the rabbit

The effects of pentobarbital (PB) anesthesia on arterial pressure, heart rate, and renal nerve activity (RNA) were studied in chronically instrumented intact rabbits and rabbits with sinoaortic baroreceptor denervation (SAD). In intact rabbits, PB caused an initial decrease in mean arterial pressure from 82 +/- 2 to 42 +/- 5 mm Hg, which then returned to the control level within 5 min. RNA increased by 144 +/- 19% in response to hypotension induced by PB then also returned to the control level within 5 min. Heart rate increased by 56 +/- 10 from 244 +/- 11 beats/min and remained elevated for 60 min. Sensitivities of baroreflex control of heart rate and RNA were markedly impaired by PB anesthesia. In SAD rabbits, PB caused hypotension (-46 +/- 5 mm Hg), which lasted for 15 min. RNA decreased initially by 80 +/- 5%, then gradually returned toward the control level. However, at 45 min after injection of PB, RNA was still depressed significantly. Tachycardia induced by PB was abolished by SAD, i.e. heart rate actually decreased by 53 +/- 10 beats/min. These results suggest that in intact rabbits steady-state effects of PB were: no change in mean arterial pressure or RNA, and tachycardia, all due to baroreflex compensation. However, in the absence of baroreflex compensation, PB elicited hypotension, bradycardia, and a decrease in RNA.     

Characteristics of the tonic activity in different groups of neurons of the superior cervical ganglion in the rabbit

The patterns of tonic activity were studied by intracellular recording from neurons of rabbit superior cervical ganglion at rest and with stimulation of chemoreceptors. According to reflex changes in the activity pattern all neurons studied were classified into three groups by the functional value. Action potentials of the first and second types may be observed in the tonic activity of all groups, that suggests the presence of dominant and accessory inputs for neurons innervating various target organs. The analysis of changes in action potentials and EPSP frequencies of tonic activity for neurons of different groups makes it possible to suggest that preganglionic fibres converging on the neurons of these groups possess a similar type of tonic activity.     

Hypoventilation recruits preganglionic sympathetic fibers with inspiration-related activity in the superior cervical trunk of the rat.

Activity in preganglionic sympathetic neurons projecting in the cervical sympathetic trunk (CST) of rats was analysed with respect to changes in the pattern of the respiratory modulation during a long lasting hypoventilation. Under normal acid-base status (pH: 7.36+/-0.04, pCO2: 42.1+/-6.1 mm Hg, pO2: 135.8+/-43 mm Hg) a maximum of activity during expiration (expiration-related activity) was observed in all nerve recordings (n = 27). No other pattern of respiratory modulation was observed under this condition. Under a hypoventilation a dissociation between the duration of phrenic nerve activity and that of the inspiratory inhibition in neurons with expiration-related activity was observed as the inhibition was significantly prolonged by 49+/-24.9% and outlasted inspiration in 5/7 multifibers. When acid-base status was systematically changed (pH: 7.15+/-0.05, pCO2: 80.4+/-11.8 mm Hg, pO2: 62.8+/-17.5 mm Hg [n = 7]) by a hypoventilation lasting for several hours activity with a maximum peak during central inspiration (inspiration-related activity) emerged and disappeared when control conditions were reestablished. Neurons with expiration-related activity showed a cardiac rhythmicity (CR) of 62.5+/-14.6% (n = 27) and were inhibited to baroreceptor stimulation whereas neurons with inspiration-related activity showed no discernible CR (23.1+/-5.1%; n = 7) and were not inhibited to baroreceptor stimulation. Furthermore, expiration-related neurons were inhibited by 32.5+/-18.3% (n = 27) during noxious cutaneous stimulation while neurons with inspiration-related activity were activated by 21.5+/-12.1% (n = 7). These findings suggest that the respiratory modulation of preganglionic sympathetic activity in the CST consists of expiration-related activity in normal acid-base status. During hypoventilation neurons with inspiration-related activity are recruited. These neurons show reflex patterns distinct from expiration-related neurons and probably constitute a subgroup of sympathetic neurons which is activated under increased respiratory drive.     

Coupling between unmyelinated peripheral nerve fibers does not involve sympathetic efferent fibers

Bidirectional coupling of action potential activity between unmyelinated fibers in the normal peripheral nerve of monkey has recently been reported. Often typical C-fiber nociceptors are identified with the coupled fibers. In this study, sympathetic stimulation and sympathetic ablation experiments demonstrated that the sympathetic nervous system is not involved in this coupling.     

Increased level of tonic sympathetic arousal in high-vs. low-alexithymic cervical dystonia patients

The purpose of this study was to assess whether alexithymia is a risk factor for autonomic dysregulation in cervical dystonia (spasmodic torticollis, ST). Alexithymia was assessed by an authorized German version of the TAS-20. In a first step, we recruited 10 ST-patients with high alexithymia scores (> 62; M = 69.2, SD = 3.0) and compared them with 10 ST-patients with low alexithymia scores (< 35; M = 28.7, SD = 4.3) on physiological and subjective responses to a cognitive and an emotional laboratory stressor. High-alexithymic ST-patients generally showed increased levels of autonomic arousal (higher SCL, more NS.SCF and lower T; 0.016 /= 57 vs. low 相似文献   

Intracranial trajectories of sympathetic nerve fibers originating in the superior cervical ganglion in the rat: WGA-HRP anterograde labeling study

Intracranial trajectories of sympathetic nerve fibers originating in the superior cervical ganglion (SCG) in the rat were investigated by means of anterograde labeling following the injection of wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP) into the unilateral SCG. The trajectory of the sympathetic fiber innervating the pineal gland and its continuing structures was found advancing along the abducent nerve, through the cavernous plexus, then along the trochlear nerve. Labeled sympathetic fibers showed two patterns of distribution in the blood vessels on the basal surface of the brain. The sympathetic fibers originating in the unilateral SCG were intermingled with those fibers from the contralateral SCG in the pineal gland, its continuing structures and the choroid plexus of the third ventricle as well as in the cerebral blood vessels.     

Spinal segmental sympathetic outflow to cervical sympathetic trunk, vertebral nerve, inferior cardiac nerve and sympathetic fibres in the thoracic vagus

The spinal segmental localization of preganglionic neurons which convey activity to the sympathetic nerves, i.e. vertebral nerve, right inferior cardiac nerve, sympathetic fibres in the thoracic vagus and cervical sympathetic trunk, was determined on the right side in chloralose anaesthetized cats. For that purpose the upper thoracic white rami were electrically stimulated with a single pulse, suprathreshold for B and C fibres, and the evoked responses were recorded in the sympathetic nerves. The relative preganglionic input from each segment of the spinal cord to the four sympathetic nerves was determined from the size of the evoked responses. It was found that each sympathetic nerve receives a maximum preganglionic input from one segment of the spinal cord (dominant segment) and that the preganglionic input gradually decreased from neighbouring segments. The spinal segmental preganglionic outflow to the cervical sympathetic trunk, thoracic vagus, right inferior cardiac nerve and vertebral nerve gradually shifted from the most rostral to the most caudal spinal cord segments. In some cases, a marked postganglionic component was found in the cervical sympathetic trunk. It was evoked by preganglionic input from the same spinal cord segments which transmitted activity to the vertebral nerve. These results indicate that there is a fixed relation between the spinal segmental localization of preganglionic neurons and the branch of the stellate ganglion receiving the input from these neurons.     

Brainstem microstimulation activates sympathetic fibers in pudendal nerve motor branch

A bilateral spino-bulbo-spinal circuit conveys information from/to the male urogenital tract and perineal muscles. This is the first electrophysiological report of another descending pathway, one which conveys output from the medullary reticular formation (MRF) to activate postganglionic sympathetic fibers contained within the motor branch of the pudendal nerve (PudM). In anesthetized rats, long latency (> 150 ms) discharges were elicited in the PudM following ipsilateral or contralateral microstimulation of the MRF. These firing bursts were not observed in rats after sectioning the lower lumbar sympathetic trunk. The most robust activation was observed when neurons in or near the lateral paragigantocellular reticular nucleus were microstimulated bilaterally. Urogenital dysfunction that occurs following severe spinal cord injury probably results from disrupting these and other supraspinal circuits.     

Adrenergic sympathectomy ablates unmyelinated fibers in the rat 'preganglionic' cervical sympathetic trunk

Classical anatomical depictions of the cervical sympathetic trunk label it as a cholinergic preganglionic structure. We studied the cervical sympathetic trunk of the rat following daily injection for 5 weeks of guanethidine monosulphate, a regimen known to selectively destroy adrenergic neurons outside of the blood-brain barrier leaving cholinergic systems and preganglionic structures intact. The drug-treated animals were compared with a group of physiologic saline-injected animals. In the drug-treated animals, there was an approximately 40% reduction in the numbers of unmyelinated fibers per unit area compared to controls. The finding of swollen and degenerative appearing unmyelinated fibers at 7 days of drug treatment confirmed that the fiber loss resulted from active axonal degeneration. The pattern of unmyelinated fiber loss was expressed as a reduction of fibers per Schwann cell-basement membrane profile with an appearance of 'empty profiles', and a conversion of large profiles (with large numbers of fibers per profile) to smaller size categories. There were no differences in axon diameters, fascicular areas, and numbers of microvessels between the groups. Microvessels were dilated in the drug-treated animals. These findings suggest that a large component of the cervical sympathetic chain in the rat consists of postganglionic adrenergic fibers which appear to intermingle with preganglionic cholinergic axons coursing through the chain.     

Baroreceptor influences on cardiac-related sympathetic nerve activity

We studied the effect of a dropped ventricular beat (i.e. loss of one cycle of pulse synchronous baroreceptor nerve activity) on the centrally generated 2-6 Hz oscillation in postganglionic sympathetic nerve discharge (SND) in cats anesthetized with Dial-urethane. The results indicate that in each cardiac cycle baroreceptor nerve activity can: (1) decrease the rate of recruitment and number of postganglionic fibers that become active and (2) advance the onset of central inhibition responsible for the abrupt decline of SND. These effects are independent of baroreceptor-mediated entrainment of the 2-6 Hz oscillation of SND to the cardiac cycle.