Inhibitory effect of pain-eliciting transcutaneous electrical stimulation on vibration-induced finger flexion reflex in the human upper limb.

We studied the effects of non-pain transcutaneous electrical stimulation (TES) and pain-eliciting TES on vibration-induced finger flexion reflex (VFR) in 12 healthy volunteers. Tonic finger flexion reflex in the upper limb was induced by the application of vibratory stimulation on the volar side of the middle fingertip in the right hand before and after TES. Non-pain TES or pain-eliciting TES was applied on the skin between the bases of the first and second metacarpals in the right hand dorsal area in a crossover design. Pain-eliciting TES inhibited VFRs significantly (Fisher's PLSD, p <0.01), compared to those of the time-control group during and after TES. VFRs were reduced approximately to 63.8% and 78.6% of prestimulation flexion force during and after pain-eliciting TES, respectively. Nonpain TES did not inhibit VFR. These results suggest that pain-conducting afferent fibers have inhibitory neuronal connection over the ipsilateral reflex circuits of VFR in the upper limb.

Neuronal histamine release elicited by hyperthermia mediates tracheal dilation and pressor response.

Whether brain histaminergic neurons contribute to the regulation of tracheal tone and peripheral vascular tone under hyperthermia was investigated in anesthetized rabbits. Histamine release from the rostral ventrolateral medulla (RVLM), the raphe nuclei, and the solitary nucleus of the medulla oblongata was significantly increased by hyperthermia. The increased histamine was significantly suppressed by 10(-6) M tetrodotoxin microdialyzed in each area. Tracheal pressure and mean arterial pressure were significantly decreased and increased by hyperthermia, respectively. An H(1)-receptor antagonist, 5 x 10(-6) M (+)-chlorpheniramine, bilaterally microdialyzed in the RVLM significantly enhanced histamine release in the RVLM as well as significantly suppressed tracheal dilation and pressor response caused by hyperthermia. These data indicate that histamine release in the medulla oblongata is enhanced by hyperthermia. The enhanced histamine is the neuronal origin and the cause of tracheal dilation and pressor response at least via H(1) receptors in the RVLM. Brain histaminergic neurons play important roles in tracheal tone and peripheral vascular tone via H(1) receptors in the RVLM and homeostasis on body temperature.

Thixotropy of rib cage respiratory muscles in normal subjects.

In this study, we searched for signs of thixotropic behavior in human rib cage respiratory muscles. If rib cage respiratory muscles possess thixotropic properties similar to those seen in other skeletal muscles in animals and humans, we expect resting rib cage circumference would be temporarily changed after deep rib cage inflations or deflations and that these aftereffects would be particularly pronounced in trials that combine conditioning deep inflations or deflations with forceful isometric contractions of the respiratory muscles. We used induction plethysmography to obtain a continuous relative measure of rib cage circumference changes during quiet breathing in 12 healthy subjects. Rib cage position at the end of the expiratory phase (EEP) was used as an index of resting rib cage circumference. Comparisons were made between EEP values of five spontaneous breaths immediately before and after six types of conditioning maneuvers: deep inspiration (DI); deep expiration (DE); DI combined with forceful effort to inspire (FII) or expire (FEI); and DE combined with forceful effort to inspire (FIE) or expire (FEE), both with temporary airway occlusion. The aftereffects of the conditioning maneuvers on EEP values were consistent with the supposition that human respiratory muscles possess thixotropic properties. EEP values were significantly enhanced after all conditioning maneuvers involving DI, and the aftereffects were particularly pronounced in the FII and FEI trials. In contrast, EEP values were reduced after DE maneuvers. The aftereffects were statistically significant for the FEE and FIE, but not DE, trials. It is suggested that respiratory muscle thixotropy may contribute to the pulmonary hyperinflation seen in patients with chronic obstructive pulmonary disease.

Expiratory time determined by individual anxiety levels in humans.

We have previously found that individual anxiety levels influence respiratory rates in physical load and mental stress (Y. Masaoka and I. Homma. Int. J. Psychophysiol. 27: 153-159, 1997). On the basis of that study, in the present study we investigated the metabolic outputs during tests and analyzed the respiratory timing relationship between inspiration and expiration, taking into account individual anxiety levels. Disregarding anxiety levels, there were correlations between O2 consumption (VO2) and minute ventilation (VE) and between VO2 and tidal volume in the physical load test, but no correlations were observed in the noxious audio stimulation test. There was a volume-based increase in respiratory patterns in physical load; however, VE increased not only for the adjustment of metabolic needs but also for individual mental factors; anxiety participated in this increase. In the high-anxiety group, the VE-to-VO2 ratio, indicating ventilatory efficiency, increased in both tests. In the high-anxiety group, increases in respiratory rate contributed to a VE increase, and there were negative correlations between expiratory time and anxiety scores in both tests. In an awake state, the higher neural structure may dominantly affect the mechanism of respiratory rhythm generation. We focus on the relationship between expiratory time and anxiety and show diagrams of respiratory output, allowing for individual personality.

Central histaminergic neurons regulate rabbit tracheal tension through the cervical sympathetic nerve.

We previously showed that stimulation of the posterior hypothalamus decreases tracheal tension and involves central histaminergic neurons. In the present study, we reveal that central histaminergic neurons project to the rostral ventrolateral medulla and affect cervical sympathetic nervous activity in rabbits. Administration of histamine into the fourth ventricle increased cervical sympathetic nervous activity and decreased tracheal tension. These effects were inhibited by administration of a histamine H receptor antagonist, pyrilamine, into the fourth ventricle. Unilateral injection of DL-homocysteic acid into the tuberomammillary nucleus increased cervical sympathetic nervous activity, an effect was antagonized by bilateral injection of pyrilamine into the rostral ventrolateral medulla. The pulse correlogram between the stimulation pulse applied to the tuberomammillary nucleus and the cervical sympathetic nerve activity showed a mode at 150 to 200 ms, which was reduced by pyrilamine administration into the fourth ventricle. Fibers anterogradely labeled by Phaseolus vulgaris leucoagglutinin (PHA-L) injected into the tuberomammillary nucleus were distributed in the A1, A2, C1, and C2 areas which are determined by tyrosine hydroxylase-immunohistochemistry. PHA-L positive neurons were in close contact with tyrosine hydroxylase-immunoreactive neurons in these four areas. Cell bodies in the tuberomammillary nucleus retrogradely labeled with fluorogold from the rostral ventrolateral medulla were immunoreactive with histamine. These results suggest that an excitatory efferent pathway projects from the tuberomammillary nucleus to the cervical sympathetic nerve and that the histaminergic neurons of this pathway influence tracheal tension through the rostral ventrolateral medulla.

Autoregulation of histamine release in medulla oblongata via H3-receptors in rabbits.

The release of histamine (HA) from the rostral ventrolateral medulla (RVL), the raphe nuclei (nR), and the solitary nucleus (nTS) was investigated in anesthetized rabbits using microdialysis and high-performance liquid chromatography. HA release upon electrical stimulation of the posterior hypothalamus (PH), where histaminergic cell bodies are located, was increased to 168% of the baseline level in the RVL (n = 6), 139% of the baseline level in the nR (n = 5), and 166% of the baseline level in the nTS (n = 4). Upon perfusion of thioperamide, an H3-receptor antagonist, via a microdialysis probe, HA release from the RVL, nR and nTS increased. The increase in HA release from the RVL, nR and nTS following thioperamide perfusion was suppressed by co-perfusion of thioperamide and an H3-receptor agonist, imetit. We found that HA is released from the RVL, nR and nTS, that the HA release from all three areas is increased upon stimulation of the PH, and that the HA release is locally influenced in opposite directions by thioperamide and imetit. These results suggest that HA release in the medulla oblongata is controlled by the PH and that H3-receptors participate in the autoregulation of HA release by providing negative feedback locally. Autoregulation of HA release via H3-receptors may be important for maintaining tonic output to the sympathetic nervous system.

Vibration-induced finger flexion reflex and inhibitory effect of acupuncture on this reflex in cervical spinal cord injury patients.

The vibration-induced finger flexion reflex (VFR) and the inhibitory effect of acupuncture on this reflex were studied in five cervical spinal cord injury patients (C-SCIs). VFR, which is a tonic finger flexion reflex induced by vibratory stimulation on the finger tip, was induced before and after acupuncture was carried out on the same hand. A stainless steel needle was inserted to the Hoku point. As in healthy subjects, VFR was performed and it was significantly inhibited by acupuncture in the C-SCIs; mean maximum VFR was 204.2 +/- S.E. 68.6 g before and 119.8 +/- S.E. 42.2 g after acupuncture. The present results suggest that at least part of the reflex center for VFR is located in the spinal cord and that part of VFR inhibition by acupuncture may be mediated via the spinal cord.

Effect of acupuncture at the Hoku point on vibration-induced finger flexion reflex in man: comparison between press needle technique, electroacupuncture, and in-situ technique.

Effects of press needle technique (PN), electroacupuncture (EA), or in-situ technique (IS) on vibration-induced finger flexion reflex (VFR) were examined in 31 healthy adults. VFR, which is tonic finger flexion evoked by vibration applied to the finger tip, was induced by vibrating the volar side of the middle finger tip before and after acupuncture. Acupuncture was applied to the Hoku point on both sides. The three techniques, each studied on separate days, inhibited VFR and there was no significant difference in VFR inhibition among the three techniques (percentage of pre-acupuncture VFR was 71.5 +/- SE 2.2% after PN, 72.6 +/- SE 2.4% after EA, and 75.6 +/- SE 2.8% after IS). The results suggest that afferent signals from muscles contracting due to electrical stimulation had no significant effect on the reflex arcs of VFR; and that the intradermal stimulation by acupuncture played a significant role in VFR inhibition.

Effect of acupuncture at the right Hoku point on bilateral vibration-induced finger flexion reflex in man: comparison between in-situ and Sparrow Pecking technique.

The purpose of this study was to compare the effect of the Sparrow Pecking (SP) technique with that of the In-Situ (IS) technique of acupuncture on vibration-induced finger flexion reflex (VFR). Subjects were 30 healthy adults. VFR, flexion movement of the vibrated finger, was induced by vibrating the volar side of the middle finger tip. The acupuncture point was the right Hoku point. Both techniques of acupuncture inhibited VFR in the ipsilateral and contralateral sides, but inhibition with SP was significantly greater than that with IS (percentage control force of VFR, mean +/- SD: with SP right, 62.1 +/- 24.6%, left, 60.6 +/- 27.9%, with IS right, 74.9 +/- 26.6%, left, 78.1 +/- 29.5%, P < 0.0005). The results suggest that SP suppresses facilitation of VFR in the reflex arcs more than IS does.

Effect of acupuncture at right Hoku point on the bilateral vibration-induced finger flexion reflex in man.

Vibration applied to the volar side of the finger tip has been reported to induce finger flexion reflex. Acupuncture is reported to inhibit this vibration-induced finger flexion reflex (VFR) in the ipsilateral hand. The purpose of this study was to investigate the effect of unilateral acupuncture in the hand on VFR in both hands. As no systematic study on the relationship between VFR and the force of voluntary contraction with no vibration (Initial Force: IF) has been reported, this relationship was studied prior to the present study on acupuncture. VFR was induced by mechanical vibration on the volar side of the middle finger tip with 10 g to 500 g IF. With approximately 300 g IF, VFR was consistent. Therefore, approximately 300 g IF was applied for VFR induction to study the effect of acupuncture on VFR. A stainless steel needle was inserted into the right Hoku point and remained inserted (in-situ technique) for 10 minutes. VFR in both hands was significantly decreased by acupuncture at the right Hoku point (% control force of VFR: right, 67.8%; left, 74.6%). The present results suggest that acupuncture in the unilateral hand influences the bilateral reflex arc of VFR.

[Rabbit immunization to induce experimental asthma--relationship between antigens and airway reactivity].

Japanese white rabbits were immunized with either alternaria or ragweed starting at birth to induce experimental asthmatic model. We studied the characteristics of contractile responses of tracheal smooth muscle isolated from these sensitized animals and compared them with non-sensitized control animals. Both sensitivity and reactivity of contraction induced by acetylcholine (ACh) were increased in the alternaria sensitized group, but only sensitivity was increased in the ragweed group. Contractile responses to electrical field stimulation were enhanced in both sensitized groups, and responses in the alternaria group were significantly greater than those in the ragweed group. In the alternaria group, atropine suppressed the contractile response to KCl, indicating that the contraction was mediated partially through a muscarinic mechanism. In the ragweed group, atropine suppressed responses to 20 mM KCl. Stimulation of the intramural nerve plexus facilitated the release of neurotransmitters, especially ACh. This was more obvious in the alternaria group than in the ragweed group. These results suggest that alternaria sensitization of rabbits produces a better model for studying changes in interaction between nerves and smooth muscle in the airway.

Inhibitory effect of acupuncture on the finger flexion reflex induced by finger tip vibration.

The effect of acupuncture on finger flexion reflex, caused by mechanical vibration applied to the finger tip, was studied by using the cross-correlation function. A stainless steel acupuncture needle was inserted into the acupuncture point called "Wai-Kuan" for 10 min. Acupuncture inhibited the reflex and suppressed the two modes seen in the cross-correlogram between unitary EMG activity of the muscle flexor digitorum superficialis and finger tip vibration with random frequency. The recovery of the primary mode, which may be via the spinal monosynaptic reflex loop, was significantly earlier than the recovery of the secondary mode, which may be via the supraspinal reflex long loop. This suggests that the distinct inhibitory effect of acupuncture takes place on the reflex at spinal and supraspinal levels.

Inhibitor effect of acupuncture on the vibration-induced grasp reflex in man.

The effect of acupuncture on the grasp reflex caused by mechanical vibrations of fingers produced by a cylinder-type vibrator (120 Hz) was studied in healthy man. As the hand grasped the vibrator during vibration, the volar surface of all fingers was simultaneously stimulated, resulting in a gradually increased force of the grasp, the vibration-induced grasp reflex (VGR). The VGR was inhibited by acupuncture with needles inserted into three acupuncture points (Shou Sanli, Chicheng and Szutu), but not into other sites in the hand.

The inhibitory effect of acupuncture on the tonic vibration reflex (TVR) in man.

The effect of acupuncture on the tonic vibration reflex (TVR) has been examined in healthy men. Vibrations (100 Hz) were applied over the muscle bellies of either finger flexion muscles or extension muscles, while finger flexions and extensions were measured by a strain attached to the middle finger. A stainless steel acupuncture needle was inserted for 10 min into an acupuncture point named "Chu-Chih (LI-II)". After the application of acupuncture, TVRs in both flexion and extension muscles were significantly less than those observed before the application of acupuncture. The inhibitory effect of acupuncture almost disappeared 10 min after removing the needle. Acupuncture transiently inhibits TVR in extension and flexion muscles in man.

Ventilatory responses to carbon dioxide and hypoxia during acupuncture anesthesia in rabbits.

Ventilatory responses to CO2 or hypoxia were examined in rabbits during acupuncture anesthesia and compared with responses during pentobarbital anesthesia. The responses during pentobarbital anesthesia were significantly less than those during acupuncture anesthesia. The results showed that acupuncture analgesia was effective during performance of these experiments.

Inhibitory effect of acpuncture on the vibration-induced finger flexion reflex in man.

The effect of acupuncture on the tonic finger flexion reflex caused by mechanical vibration of the index finger was studied in healthy man. The volar side of the index finger was tapped by a vibrator (100 Hz), while flexion forces were recorded. A silver needle inserted into the acupuncture point (Wai-Kuan) inhibited the vibration-induced finger flexion reflex. In this study, the inhibitory effect of acupuncture on the reflex contraction, rather than pain sensation and analgesia, was demonstrated.