Effect of electrical stimulation of the trigeminal nucleus caudatus on the blood microvessel permeability in the eye in normal and capsaicin-treated rats

Electrical stimulation of the trigeminal caudate nucleus increased permeability of the eye blood microvessels in rats. Ten days after capsaicin pre-treatment (total dose 150 mg/kg, s/c for 2 days: 20, 30, 50, 50 mg/kg) the electrical stimulation did not evoke any changes of the microvascular permeability in the eye. The data suggest that the effect of the stimulation is mediated through capsaicin-sensitive neurones of the trigeminal ganglion.     

GABAB receptors in the NTS mediate the inhibitory effect of trigeminal nociceptive inputs on parasympathetic reflex vasodilation in the rat masseter muscle

The present study was designed to examine whether trigeminal nociceptive inputs are involved in the modulation of parasympathetic reflex vasodilation in the jaw muscles. This was accomplished by investigating the effects of noxious stimulation to the orofacial area with capsaicin, and by microinjecting GABA(A) and GABA(B) receptor agonists or antagonists into the nucleus of the solitary tract (NTS), on masseter hemodynamics in urethane-anesthetized rats. Electrical stimulation of the central cut end of the cervical vagus nerve (cVN) in sympathectomized animals bilaterally increased blood flow in the masseter muscle (MBF). Increases in MBF evoked by cVN stimulation were markedly reduced following injection of capsaicin into the anterior tongue in the distribution of the lingual nerve or lower lip, but not when injected into the skin of the dorsum of the foot. Intravenous administration of either phentolamine or propranolol had no effect on the inhibitory effects of capsaicin injection on the increases of MBF evoked by cVN stimulation, which were largely abolished by microinjecting the GABA(B) receptor agonist baclofen into the NTS. Microinjection of the GABA(B) receptor antagonist CGP-35348 into the NTS markedly attenuated the capsaicin-induced inhibition of MBF increase evoked by cVN stimulation, while microinjection of the GABA(A) receptor antagonist bicuculline did not. Our results indicate that trigeminal nociceptive inputs inhibit vagal-parasympathetic reflex vasodilation in the masseter muscle and suggest that the activation of GABA(B) rather than GABA(A) receptors underlies the observed inhibition in the NTS.     

Confluence of barosensory and nonbarosensory inputs at neurons in the ventrolateral medulla in rabbits

In urethane-anesthetized rabbits, 209 spontaneously active neurons that responded to stimulation of aortic nerve A fibers were found within the ventrolateral medulla (VLM). The neurons, termed barosensory VLM neurons, were inhibited, except for three instances, by stimulation of A fibers. Forty-seven percent of barosensory VLM neurons tested (74 of 159) were activated antidromically by electrical stimulation of the dorsolateral funiculus at the C2 level. Activity of barosensory VLM neurons was enhanced by stimulation of carotid body chemoreceptors or the posterior hypothalamic area, whereas it was diminished by increases in arterial pressure elicited by injection of phenylephrine. Barosensory VLM neurons responded variously to stimulation, with two to three pulses at 40 or 100 Hz, of spinal afferents of cutaneous and muscle origins and the spinal trigeminal complex. Although stimulation of one group of somatosensory fibers could evoke different patterns of neuronal responses consisting of excitatory and inhibitory components, the following responses were most often encountered. Group II cutaneous afferents caused an inhibition. Recruitment of group III afferents brought about a brief excitatory component preceding it. Activation of group IV cutaneous fibers added a long latency excitatory component. Excitation of groups III and IV muscle afferents most often resulted in an inhibition, whereas stimulation of the spinal trigeminal complex elicited various combinations of excitatory and inhibitory components. These results are consistent with the view that neurons in the ventrolateral medulla receive barosensory and nonbarosensory inputs from various peripheral and central sources and participate in the control of sympathetic vasomotor activity and arterial pressure.     

Effects of stimulating the central gray matter on neuronal response in the cat medial thalamic nuclei

This study was performed on the effects of stimulating the midbrain central gray matter (CGM) on neuronal response in the association medial thalamic nuclei evoked by stimulation of A-alpha and A-delta fibers of the infraorbital nerve and the caudal nucleus of the spinal trigeminal tract (CN STT) and tooth pulp stimulation using cats anesthetized by thiopental-chloralose as experimental animals. Stimulating the CGB with trains of stimuli was found to evoke an excitatory response in a percentage of the neurons tested, in which latency fluctuated between 15 and 40 msec. Applying conditioned stimuli to the CGM caused suppression of response to afferent impulses in neurons belonging to the "convergent" and "low" and "high" threshold groups. Responses induced by stimulating tooth pulp and A-delta fibers showed 100% inhibition as compared with 86% during A-alpha fiber and infraorbital nerve stimulation. The fact that stimulating the CGM produces an inhibitory effect on the response of thalamic neurons evoked by stimulation of both peripheral afferents and the CN STT would indicate that the CGM can exert a direct action on thalamic neuronal activity.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 19, No. 5, pp. 660–665, September–October, 1987.     

Wide-pulse-width, high-frequency neuromuscular stimulation: implications for functional electrical stimulation.

Electrical stimulation (1-ms pulses, 100 Hz) produces more torque than expected from motor axon activation (extra contractions). This experiment investigates the most effective method of delivering this stimulation for neuromuscular electrical stimulation. Surface stimulation (1-ms pulses; 20 Hz for 2 s, 100 Hz for 2 s, 20 Hz for 3 s) was delivered to triceps surae and wrist flexors (muscle stimulation) and to median and tibial nerves (nerve stimulation) at two intensities. Contractions were evaluated for amplitude, consistency, and stability. Surface electromyograph was collected to assess how H-reflexes and M-waves contribute. In the triceps surae, muscle stimulation produced the largest absolute contractions (23% maximal voluntary contraction), evoked the largest extra contractions as torque increased by 412% after the 100-Hz stimulation, and was more consistent and stable compared with tibial nerve stimulation. Absolute and extra contraction amplitude, consistency, and stability of evoked wrist flexor torques were similar between stimulation types: torques reached 11% maximal voluntary contraction, and extra contractions increased torque by 161%. Extra contractions were 10 times larger in plantar flexors compared with wrist flexors with muscle stimulation but were similar with nerve stimulation. For triceps surae, H reflexes were 3.4 times larger than M waves during nerve stimulation, yet M waves were 15 times larger than H reflexes during muscle stimulation. M waves in the wrist flexors were larger than H reflexes during nerve (8.5 times) and muscle (18.5 times) stimulation. This is an initial step toward utilizing extra contractions for neuromuscular electrical stimulation and the first to demonstrate their presence in the wrist flexors.     

Electromagnetic stimulation blocks isometric twitch contraction in the frog sciatic nerve-gastrocnemius muscle preparation

The effect of electromagnetic stimulation (EMS) on nerve conduction and muscle twitch contraction was studied in isolated sciatic nerve-gastrocnemius muscle of the frog. Electrical stimulation (ES) of the sciatic nerve produced twitch contractions in the gastrocnemius muscle and these responses were reduced and eventually blocked by EMS, applied to the nerve simultaneously with ES, from a d.c. source at a certain frequency and duration of the induced current. The EMS-induced inhibition of the twitch contractions was reversible, and this depended on the induced current and its duration. The possibility that other factors may have contributed to the inhibition of twitch contractions, such as a rise in temperature, was also investigated. It was concluded that EMS inhibited indirectly-elicited twitch contractions produced by ES in the frog nerve-muscle preparation.     

Trigeminal nerve: the possible origin of substance p-nergic response in isolated rabbit iris sphincter muscle

We determined the effects of trigeminal nerve denervation on the noncholinergic, nonadrenergic response to electrical transmural stimulation of the isolated rabbit iris sphincter muscle. The left ophthalmic nerve (first branch of the trigeminal nerve) was cut at the intracranial, peripheral site of the trigeminal ganglion and five to ten days later, the iris sphincter muscle isolated from the left eye (operated side) was found to produce a fast cholinergic contraction in response to electrical transmural stimulation and there was no evidence of noncholinergic, nonadrenergic contractions. On the other hand, in the iris sphincter muscle isolated from the right eye (control side), electrical transmural stimulation produced both cholinergic and noncholinergic, nonadrenergic contractile responses. Capsaicin and bradykinin produced noncholinergic, nonadrenergic contractile responses in the muscle from the control side, while in the iris sphincter from the trigeminally denervated eye there was no such response to application of these drugs. Exogenous substance P (SP) and carbachol produced a strong contractile response in both the trigeminally innervated and denervated sphincter muscles. Somatostatin, vasoactive intestinal polypeptide (VIP) and enkephalin were without effects. These observations suggest that the noncholinergic, nonadrenergic responses to electrical transmural stimulation are derived from the trigeminal nerve and that the mediator involved is probably SP or a related peptide.     

Electrical Vestibular Stimuli to Enhance Vestibulo-Motor Output and Improve Subject Comfort

Electrical vestibular stimulation is often used to assess vestibulo-motor and postural responses in both clinical and research settings. Stochastic vestibular stimulation (SVS) is a recently established technique with many advantages over its square-wave counterpart; however, the evoked muscle responses remain relatively small. Although the vestibular-evoked responses can be enhanced by increasing the stimulus amplitude, subjects often perceive these higher intensity electrical stimuli as noxious or painful. Here, we developed multisine vestibular stimulation (MVS) signals that include precise frequency contributions to increase signal-to-noise ratios (SNR) of stimulus-evoked muscle and motor responses. Subjects were exposed to three different MVS stimuli to establish that: 1) MVS signals evoke equivalent vestibulo-motor responses compared to SVS while improving subject comfort and reducing experimentation time, 2) stimulus-evoked vestibulo-motor responses are reliably estimated as a linear system and 3) specific components of the cumulant density time domain vestibulo-motor responses can be targeted by controlling the frequency content of the input stimulus. Our results revealed that in comparison to SVS, MVS signals increased the SNR 3–6 times, reduced the minimum experimentation time by 85% and improved subjective measures of comfort by 20–80%. Vestibulo-motor responses measured using both EMG and force were not substantially affected by nonlinear distortions. In addition, by limiting the contribution of high frequencies within the MVS input stimulus, the magnitude of the medium latency time domain motor output response was increased by 58%. These results demonstrate that MVS stimuli can be designed to target and enhance vestibulo-motor output responses while simultaneously improving subject comfort, which should prove beneficial for both research and clinical applications.     

Electrical activity in sympathetic fibres to hind limb muscles of the cat produced by hypothalamic stimulation

Electrical stimulation of the "Defence Area" of the hypothalamus in anaesthetized cats was accomplished by stereotaxic placement of bipolar stainless steel electrodes; the spinal cord was sectioned at L4. The muscle blood flow in one hind limb was recorded with an electromagnetic flowmeter. Increases of between 100% and 300% were observed during hypothalamic stimulation. Electroneurographic recordings from small nerve filaments supplying tibialis anterior muscle revealed two populations of neurones whose activity was abolished by lumbar sympathectomy. It appears that the increased blood flow in skeletal muscle during stimulation of the hypothalamic "Defence Area" is brought about by a simultaneous inhibition of vasoconstrictor activity and increase in cholinergic vasodilator discharge.     

Excitation and inhibition of neurons in the trigeminal nucleus caudalis following periaqueductal gray stimulation

Electrical stimulation (3-4 shocks, 300 Hz, 30-150 microamperemeter) of the periaqueductal gray matter (CG) or dorsal raphé nucleus (DR) of decerebrate cats reduced or abolished the jaw-opening reflex response evoked by stimulation of either the tooth pulp or infraorbital nerve. In addition, CG or DR stimulation inhibited the response of 12 out of 16 trigeminal nucleus caudalis neurons to activation of their sensory afferent inputs. Ten other neurons recorded in the same sites, and often at the same time, but which did not respond to the sensory inputs utilized, were excited by identical stimuli to CG or DR. This excitatory response was blocked by intravenously administered naloxone (0.1-0.2 mg/kg). It is suggested that those neurons which are excited by CG and DR stimulation may be interneurons involved in pre- and post-synaptic inhibition of sensory transmission during stimulus-produced or narcotic analgesia.     

Corticospinal control of soleus motoneurons in man

Electrical or magnetic stimulation of the human motor cortex causes a strong, short latency facilitation of tibialis anterior (TA) motoneurons but only weak, longer latency changes in the excitability of soleus (SOL) motoneurons. The facilitation of TA motoneurons has been attributed to the monosynaptic action of the "fast" corticospinal pathway. The present study further investigates the cortical control of soleus motoneurons in man. In tests of reaction time to auditory stimuli, normal subjects took significantly longer to activate soleus motoneurons than tibialis anterior motoneurons. Thus we could not demonstrate the existence of a "fast" pathway from the brain to SOL motoneurons that, for some reason, is not activated by magnetic stimulation. The hypothesis that the cortex might control soleus motoneurons indirectly by modulation of the Ia input from muscle spindles was tested. Magnetic stimulation of the cortex was used to condition the facilitation of soleus motoneurons resulting from the stimulation of group I fibres in the tibial nerve. There were no consistent changes in Ia facilitation. We conclude (i) that there is no evidence so far that SOL motoneurons are excited by a direct pathway from the cortex (similar to that projecting to TA motoneurons) and (ii) that the observed changes in firing probability of soleus motoneurons produced by magnetic stimulation over the motor cortex do not result from modulation of presynaptic inhibition of Ia afferents.     

Voltage activated calcium channels in somatic muscle of filarial nematode Setaria cervi

Acetylcholine (Ach), levamisole and pyrantel pamoate all cause stimulation of spontaneous rhythmic movements of whole worm and nerve muscle preparation of filarial nematode Setaria cervi. These stimulant effects are manifested only in the presence of available Ca2+ or extracellular Ca2+. Electrical stimulation of nerve muscle preparation of Setaria cervi elicited depolarization and increase in amplitude and tone of contractions. Electrical current stimulates Ca2+ entry leading to depolarization and during the phase of depolarization addition of any of the three stimulants viz. Ach, levamisole or pyrantel pamoate fails to elicit any response on nerve muscle preparation. The findings indicate that electrical stimulation, excitatory neurotransmitter Ach and stimulant anthelmintics levamisole and pyrantel pamoate all produce their stimulant effect by triggering entry of Ca2+ into the muscle cell. Further, blocking the calcium channels by nifedepine and thereby the entry of Ca2+ into the cells blocks the stimulant effect of Ach levamisole and pyrantel pamoate.     

Functional properties of interneurons of the masticatory reflex

Interneurons of the supratrigeminal nucleus, transmitting effects from the sensory and motor branches of the trigeminal nerve to motoneurons of the muscles of mastication were investigated. Two groups of interneurons with different functional connections were found. The first group (A) contains neurons excited during stimulation of the sensory branches and the motor nerve to the digastric muscle (A₁), neurons excited during stimulation of sensory branches and high-threshold afferents of the motor nerve to the masseter muscle (A₂), and neurons excited only by low-threshold afferents of the motor nerve to the masseter muscle (A₃). Neurons of the second group (B) were activated only by sensory fibers of the trigeminal nerve. It is postulated that interneurons of group A transmit inhibitory effects to motoneurons of antagonist muscles of the lower jaw. Group B interneurons participate in the transmission of excitatory influences to motoneurons of the digastric muscle.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 150–157, March–April, 1972.     

Exercise-induced translocation of protein kinase C and production of diacylglycerol and phosphatidic acid in rat skeletal muscle in vivo. Relationship to changes in glucose transport

Contraction-induced translocation of protein kinase C (Richter E.A., Cleland, P.J.F., Rattigan, S., and Clark, M.G. (1987) FEBS Lett. 217, 232-236) implies a role for this enzyme in muscle contraction or the associated metabolic adjustments. In the present study, this role is further examined particularly in relation to changes in glucose transport. Electrical stimulation of the sciatic nerve of the anesthetized rat in vivo led to a time-dependent translocation of protein kinase C and a 2-fold increase in the concentrations of both diacylglycerol and phosphatidic acid. Maximum values for the latter were reached at 2 min and preceded the maximum translocation of protein kinase C (10 min). Stimulation of muscles in vitro increased the rate of glucose transport, but this required 20 min to reach maximum. There was no reversal of translocation or decrease in the concentrations of diacylglycerol and phosphatidic acid even after 30 min of rest following a 5-min period of stimulation in vivo. Translocation was not influenced by variations in applied load at maximal fiber recruitment but was dependent on the frequency of nontetanic stimuli, reaching a maximum at 4 Hz. The relationship between protein kinase C and glucose transport was also explored by varying the number of tetanic stimuli. Whereas only one train of stimuli (200 ms, 100 Hz) was required for maximal effects on protein kinase C, diacylglycerol, and phosphatidic acid, more than 35 trains of stimuli were required to activate glucose transport. It is concluded that the production of diacylglycerol and the translocation of protein kinase C may be causally related. However, if the translocated protein kinase C is involved in the activation of glucose transport during muscle contractions, an accumulated exposure to Ca2+, resulting from multiple contractions, would appear to be necessary.     

Interaction between segmental and descending intersegmental reflexes in lumbar motoneurons

The effects of segmental reflexes on descending intersegmental reflexes to stimulation of forelimb afferents were studied in anesthetized cats by recording postsynaptic responses from single motoneurons. Interaction between these influences was found to be reciprocal in character for groups of neurons with primary connections with afferents of the superficial and deep branches of the peroneal nerve and afferents of the nerve to the gastrocnemius muscle. Excitatory postsynaptic responses arising in groups of motoneurons of the peroneal nerve to stimulation of forelimb afferents underwent profound and prolonged inhibition during conditioning stimulation of afferents in the deep and superficial peroneal nerves. Activation of segmental afferents during conditioning stimulation of the gastrocnemius nerve was accompanied by inhibition of excitatory intersegmental responses and deinhibition of inhibitory responses in motoneurons of the gastrocnemius muscle. Segmental inhibition of intersegmental descending impulse activity appeared in the interneuron system of the segmental reflex centers connecting the descending propriospinal tracts with the motoneurons of these centers.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 4, No. 2, pp. 16872-175, March–April, 1972.     

家兔延髓腹侧表面加压区与压力感受性反射的关系

实验在乌拉坦麻醉、三碘季铵酚制动和人工呼吸的41只家兔进行。电刺激延髓腹侧面加压区(VSMp)引起肾交感神经电活动(RSNA)增强和动脉血压升高。电刺激主动脉神经(AN)则导致RSNA抑制和动脉血压下降。在下列实验条件下,刺激VSMp所致的交感兴奋性效应均不受影响:(1)同时刺激VSMp和AN;(2)刺激AN期间插入VSMp刺激;(3)刺激VSMp期间插入AN刺激。但刺激AN所致的交感抑制性效应却被明显地抑制。提示兴奋VSMp的交感兴奋性效应可调制压力感受性反射的交感抑制性成分,两者之间的动态平衡是维持静态动脉血压水平的基础。     

Stimulation-Induced Release of Coexistent Transmitters in the Prefrontal Cortex: An In Vivo Microdialysis Study of Dopamine and Neurotensin Release

Extracellular fluid levels of dopamine and neurotensin in the rat prefrontal cortex were measured using in vivo microdialysis. Electrical stimulation of the median forebrain bundle resulted in increased release of both dopamine and neurotensin from the prefrontal cortex. Thus, stimulation of neurons in which dopamine and neurotensin are colocalized can evoke the in vivo release of both substances.     

Diaphragmatic fatigue in the rat

We studied fatigue of rat diaphragm in response to repetitive brief and prolonged electrical stimulation of the phrenic nerve, at 0.2, 1-100 Hz. Low and high frequency of stimulation produced twitch and tetanic contractions in the rat diaphragm. A mean maximum twitch tension of 1.4 +/- 0.1 g was produced at 1 Hz, and a mean maximum tetanic tension of 5.6 +/- 0.3 g was obtained at 100 Hz (means +/- S.E., n = 8). Twitch and tetanic fatigue was produced at all frequencies of stimulations, but with different time scale, or duration, and with different number of stimuli delivered to the muscle. At low rates of stimulation, e.g. 10 Hz, fewer stimuli were needed to fatigue the muscle (3000 in 5 min), whereas at high rates of stimulation, e.g. 50 Hz, more stimuli were needed to fatigue the muscle (6600 in 2.2 min). The amplitude of the tetanic tensions elicited at 10 and 50 Hz, at the end of 5 or 2 min fatiguing stimulation, was 39 +/- 2.7% and 80 +/- 3.1% of their respective control tensions (2.8 +/- 0 2 g and 5.3 +/- 0.5 g, n = 8, P 0.001). It was concluded that fatigue in the rat diaphragm depended on the frequency and duration of stimulation as well as on the number of stimuli delivered to the muscle. Various mechanisms of muscle fatigue are described in the discussion to explain the observations made in the present investigation.     

Neurotrophins and their receptors in rat peripheral trigeminal system during maxillary nerve growth

We examined the expression of the neurotrophins (NTFs) and their receptor mRNAs in the rat trigeminal ganglion and the first branchial arch before and at the time of maxillary nerve growth. The maxillary nerve appears first at embryonic day (E)10 and reaches the epithelium of the first branchial arch at E12, as revealed by anti-L1 immunohistochemistry. In situ hybridization demonstrates, that at E10- E11, neurotrophin-3 (NT-3) mRNA is expressed mainly in the mesenchyme, but neurotrophin-4 (NT-4) mRNA in the epithelium of the first branchial arch. NGF and brain-derived neurotrophic factor (BDNF) mRNAs start to be expressed in the distal part of the first brachial arch shortly before its innervation by the maxillary nerve. Trigeminal ganglia strongly express the mRNA of trkA at E10 and thereafter. The expression of mRNAs for low-affinity neurotrophin receptor (LANR), trkB, and trkC in trigeminal ganglia is weak at E10, but increases by E11-E12. NT-3, NT-4, and more prominently BDNF, induce neurite outgrowth from explant cultures of the E10 trigeminal ganglia but no neurites are induced by NGF, despite the expression of trkA. By E12, the neuritogenic potency of NGF also appears. The expression of NT-3 and NT-4 and their receptors in the trigeminal system prior to target field innervation suggests that these NTFs have also other functions than being the target-derived trophic factors.     

Sensory interaction with central ‘generators’ during respiration in the dogfish

Summary The activity in sensory and motor nerves of the gills was recorded from selected branches of the vagus nerve in decerebrate dogfish,Scyliorhinus canicula. Vagal motoneuronal activity was observed at the start of the rapid pharyngeal contraction and was followed by sensory nerve activity which preceded the slow expansion phase. Rhythmical vagal motoneuronal activity was still present after all movements had been prevented by curare paralysis although the frequency of the rhythm was higher than in the ventilating fish. Electrical stimulation of vagal sensory fibres had 3 effects on the ventilatory movements. (1) It evoked a reflex contraction of several gill muscles after a latency of about 11 ms. (2) It could reset the respiratory cycle because a stimulus given during expansion delayed the onset of the subsequent contraction. (3) The stimulus could entrain the rhythm if it was given continuously at a frequency close to that of ventilation. The vagal motor rhythm was disrupted by trigeminal nerve stimulation in the paralyzed fish but not if the motor rhythm was being entrained by vagal nerve stimulation. Vagal sensory activity may be important, therefore, in maintaining the stability of the generating circuits.Abbreviation LED Light emitting diode