Sympathetic Responses in Caloric Stimulation:Role in the Cardiovascular Control of Anesthetized Rats / 航天医学与医学工程

Objective To explore the potential connection between sympathetic response, heart rate and blood pressure modulation after caloric irrigation in order to study the role of vestibular stimuli in cardiovascular control. Method Efferent splanchnic nerve firing rates, ECG and blood pressure were recorded simultaneously during caloric stimuli on intact anesthetized(CON) rats(n=5), sinoaortic denervated (SAD)rats(n=5) and bilateral vestibular destroyed (VD) rats(n=5). Result It was found that after caloric stimulation with ice water mean blood pressure CON rats with intact reflex became lower and the mean heart rates became slower, splanchnic sympathetic nerve activities increased for a moment and then dropped significantly. SAD rats had significant stronger splanchnic sympathetic nerve activities VD rats after caloric stimulation, and their blood pressures changed to apposite directions. The coupled respiratory component on splanhnic sympathetic nerve activities were strongly affected by the caloric stimulation. Conclusion It is suggested that semicircular canal stimulation participate at least in the short-term blood pressure control mechanism and the role of central nervous system on respiratory drive may also be involved. Baro-reflex and vestibular afferent may play different role in the control of blood pressure they may work synergically in some physiological control processed.

Premature Reversal Caloric Nystagmus in a Patient withMedulloblastoma, Originated from the 4th Ventricle

Some individuals may demonstrate a secondary phase nystagmus (SPN) following the caloric irrigation. It has been stated that if a SPN begins prior to 140 seconds after the onset of caloric stimulation and if the magnitude of the slow phase velocity is greater than 6 degrees/sec, then a premature reversal caloric nystagmus (PRCN) is said to exit. Thus far, there have been no reports describing PRCN in Korea. We described a typical PRCN in a patient with medulloblastoma within the 4th ventricle. The patient had a gaze-evoked horizontal and upbeating nystagmus. However, there was no indication of spontaneous nystagmus. A monothermal caloric test was administered. The initial left beating primary phase nystagmus was subsided at 60 seconds after right cold water stimulation and at 110 seconds, a right beating SPN with 14 degrees/sec of slow phase velocity was appeared and was continuous for 240 seconds. Although the precise mechanism of PRCN is unknown, vestibular nuclei damage may be related.

Electromyographic Changes Induced by Caloric Stimulation of the Semicircular Canals and by Neck Movement. Investigation of the F wave on the evoked electromyograms of the upper extremity and the surface electromyograms of the posterior cervical region / 全日本鍼灸学会雑誌

We assumed that changes in the excitability of motor nerves play some role in the stiffness of the neck, shoulders, and extremities in patients with vertigo. To obtain a better understanding of this phenomenon, we stimulated the receptors involved in body equilibrium with external stimuli, i.e., 1) caloric stimulation of the semicircular canals and 2) neck movements, and investigated changes in the F wave and the surface electromyogram (S-EMG) of the posterior cervical region.<BR>The subjects were 40 healthy adults. Caloric stimulation of the semicircular canals was performed by infusing15°C water, and changes in the F wave examined. In addition, changes in the S-EMG by stimulation at temperatures of 5°C or 44°C were investigated. We examined changes in the F wave by the neck movements in association with theresults of the blindfold ed vertical writing test. The F wave of a patient with vertigo was also examined.<BR>During vertigo induced by caloric stimulation of the semicircular canals, the excitability of the F wave on both the stimulated and non-stimulated sides increased, the S-EMGs showed decreased excitability on both the stimulated and non-stimulated sides during maximum voluntary contraction in the subject who experienced severe vertigo, nystagmus, and nausea. The changes in the F wave induced by the neck movements were small. However, excitability increased more significantly during posterior flexion than during other movements, and the angle of deviation of the letters written blindly tended to deviate most markedly toward the left during posterior flexion. The F wave of the patient with vertigo showed excitability, but it tended to decrease as the vertigo diminished.<BR>These findings suggest that vertigo is accompanied by changes in the excitability of motor nerves. These changes are somehow related to the muscle stiffening that results from vertigo.