Naohisa Fukuda

Responses of posterior hypothalamic neurons to electrical stimulation of the inferior alveolar nerve and distension of stomach with cold and warm water

Summary Responses of neurons in the posterior hypothalamus to electrical stimulation of the inferior alveolar nerve and distension of the stomach with cold and warm water were studied in encephale isolepreparations of cats. The mean firing rate of spontaneous unit discharges of the hypothalamic neurons was6.2 ± 2.9 (S.E.)/sec. About half of the units showed the pattern of exponential distribution, and the other half exhibited the distribution with 2–4 modes, gamma distribution atλ = 2, and rectangular distribution. More than half of the hypothalamic neurons responded to electrical stimulation of the inferior alveolar nerve at 20 c/sec in frequency, and the increased response dominated in the responsive neurons. The decreased response and biphasic responde were also found. Most of the units responsive to the somatosensory stimulation responded to the intragastric infusion of cold water but not warm water. The interval histogram of unit discharges was also modified by the infusion of cold water. It is concluded that the posterior hypothalamic neurons respond nonspecifically to afferent forms of stimulation.

Responses of Single Neurons of the Vestibular Nuclei to Lateral Tilt and Caloric Stimulation in the Intact and Hemilabyrinthectomized Cats

Responses of unitary discharges of the vestibular nuclei to lateral tilt and caloric stimulation were studied in the unanesthetized encephale isole preparations of intact and hemilabyrinthectomized cats. The responses of firing rate of 93 units to lateral tilt were classified into 5 groups: increased type. (increase with lateral tilt to either or both directions), decreased type (decrease with lateral tilt to either or both directions), reversed type-I (increase with ipsilateral and decrease with contralateral tilt), reversed type-II (decrease with ipsilateral and increase with contralateral tilt), and refractory type (refractory with lateral tilt to both directions). The most dominant pattern of the responses to lateral tilt was the decreased type (60.2%). On the other hand, more than half of the vestibular units (61.3%) showed reverse changes in frequency to caloric stimulation with cold and warm water. Two main types of units were localized in the vestibular nuclei: one increased the frequency in respo...

The mechanism of antagonism between apomorphine and metoclopramide on unit discharges from nuclear structures in the brainstem of the cat

Abstract Effects of apomorphine and metoclopramide were studied on the spontaneous unit discharges in the single neurons of nuclear structures of brainstem in the ence´phale isole´preparations of cats. Apomorphine increased significantly the spontaneous discharge frequencies of single neurons in the Nucleus tractus solitarii, but did not influence the frequencies in the Nucleus vestibularis lateralis and Nucleus sensorius superior n. trigemini and the number of spikes per volley in the inspiratory unit discharges. Metoclopramide decreased significantly the firing rate of unit discharges in the Nucleus tractus solitarii and Nucleus vestibularis lateralis, while the unit discharges of the Nucleus sensorius superior n. trigemini and the rhythmic unit discharges corresponding to inspiration were not modified by metoclopramide. The acceleration of spontaneous discharge frequencies of the Nucleus tractus solitarii induced by apomorphine was completely blocked by the supplement of metoclopramide. Metoclopramide prevented retching and vomiting elicited by electrical stimulation of the Nucleus tractus solitarii. In some animals, metoclopramide produced a transient alert pattern in the cortical and hippocampal EEG and depressed slightly the recruiting response. However, it did not affect the reticular arousal response and the evoked click potentials in the auditory cortex.