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J H Pazo

Publications and source records attributed to J H Pazo.

46 records · Page 3Linked to original sources
PubMed1981

Electrophysiological evidence for the existence of caudate-caudate connections.

Experiments were performed in cats unanesthetized and paralyzed with Flaxedil. The stimulation of the right caudate elicited in the contralateral nucleus, biphasic positive-negative field potentials with latencies between 11-20 msec and peak to peak amplitudes of 132-216 microv. These were the shortest latencies and the highest amplitudes for those potentials evoked by stimulation of the symmetrical positions to recording electrode. However, no responses could be evoked in the caudate tail by stimulation of any part of the opposite nucleus. Lesions of cerebral cortex (sensorimotor cortex or hemidecortication) and thalamus (center median-parafascicular complex and massa intermedia) left the evoked responses in the caudate nucleus unchanged. However, the evoked potentials were suppressed by section of the corpus callosum. Our results suggest direct connections between both caudates, through the corpus callosum.

Animals↗
PubMed1977

Substantia nigra and somatosensory evoked responses in the caudate nucleus.

The nigro-caudate relationships were studied in fifteen adult anesthetized cats, paralyzed with Flaxedil. Single shocks applied to substantia nigra (SN) evoked biphasic field potentials in the ipsilateral caudate nucleus. Similar positive-negative waves were recorded in the caudate nucleus by sciatic stimulation, although with longer latencies. A triphasic field potential was also observed after cerebral peduncle stimulation. Conditioning stimuli applied to the SN at varying time intervals prior to sciatic stimulation did not modify the test response. In contrast, conditioning stimulation of the cerebral peduncle produced a marked inhibition between 25 and 100 msec. Recovery was complete after 200 msec. The present observations indicate that nigral stimulation does not influence the pool of neurons responding to sciatic nerve in the caudate nucleus. On the other hand, the cerebral peduncles exert an inhibitory action on such activity.

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PubMed1976

Caudate-putamen and globus pallidus influences on a visceral reflex.

The electrical stimulation of the rostral striatum in rats has two different influences on bladder motility. Stimulus applied to the dorsomedial caudoputamen nucleus elicited vesical contractions and increased excitability of micturition reflex. Stimulation of the ventromedial caudoputamen suppressed detrusor contractions and increased the micturition threshold. Similar inhibitory effects were found by electrical stimulation of the globus pallidus. The possible mechanisms involved and the relationship with the clinical finding of bladder dysfunction in patients with extrapyramidal disease, are discussed in view of their anatomical and functional relationships to the vesicomotor centers.

Animals↗
PubMedDate not supplied

Effects of melatonin on spontaneous and evoked neuronal activity in the mesencephalic reticular formation.

The acute effects of melatonin on the spontaneous activity of single cells in the mesencephalic reticular formation were studied in 40 male rats unanesthetized and immobilized with Flaxedil. One hundred and ten neurons were explored. Only 64 modified their spontaneous activity after the intravenous administration of melatonin. This response consisted of an increase in neural firing (6 neurons), decrease (55 neurons) and biphasic response of decrease and increase (3 neurons). When the effect of melatonin on the evoked activity in the mesencephalic neurons by peripheral stimulation (sciatic and photic) was checked an increase of the number of neurons that showed inhibitory responses to photic stimulation was found. No changes in blood pressure and EEG were observed at the doses of melatonin used (200, 400 and 600 micrograms/100 g of body weight). However, with doses of 600 micrograms a tendency toward synchronization was seen in the EEG. The present observations indicate an inhibitory effect of melatonin on the spontaneous neuronal activity of the mesencephalic reticular formation. This effect may contribute to the changes in the sleep-wakefulness cycle and anticonvulsant action attributed to this hormone.

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