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V Perciavalle

Publications and source records attributed to V Perciavalle.

At least 55 records · Page 3Linked to original sources
PubMed1987

Substantia nigra influences on the reticulospinal neurons: an electrophysiological and ionophoretic study in cats and rats.

The influences exerted by the substantia nigra on reticulospinal neurons and the nature of the synaptic transmitter subserving these projections have been studied in adult cats and rats. Nigral stimulation evokes discharge changes in a significant number of reticulospinal cells (32.4% in cats and 39.1% in rats) on both ipsi- and contralateral sides. The responses were short-latency inhibitions (69.5% in cats and 76.5% in rats), short-latency excitations (22.2% in cats and 23.6% in rats) and in the remaining few cases long-latency excitations. Short-latency excitations, quite similar to the nigra-induced ones, were the predominant response pattern (95.2% in cats and 96.9% in rats) elicited on reticulospinal cells following stimulation of cerebral peduncle. The stimulation of substantia nigra in rats submitted to chronic ablation of sensorimotor cortex elicited only inhibitory responses while stimulation of nigral area in rats with intranigral injection of kainic acid was still capable of evoking short-latency excitations but not short-latency inhibitions. Therefore, the former can be ascribed to activation of corticoreticular fibers running in the cerebral peduncle whereas the latter can be considered as depending on activation of nigral efferents. The nigra-influenced cells were both 'fast' and 'slow' reticulospinal neurons and resulted mainly located in most rostral regions of reticular formation. Ionophoretic application of GABA suppressed the spontaneous firing of reticulospinal cells while no effect was observed following application of dopamine. The nigra-induced inhibitions were abolished by GABA-antagonist bicuculline and not by dopamine-antagonist fluphenazine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Basal ganglia influences on the cerebellum of the cat.

The changes in firing rate of intracerebellar nuclear neurons following electrical stimulation of the contralateral basal ganglia were investigated in adult cats, in which antidromic activation of cortico-pontine and/or cortico-olivar fibers arising in the area 6 had been excluded by chronic ablation of the motor cortex. Activation of putamen and caudate nucleus induced discharge changes in a low percentage (below 12.5%) of both medial and lateral cerebellar nuclei neurons, while stimulation of globus pallidus and especially of entopeduncular nucleus modified the spontaneous discharge of a greater percent of cells (up to 29%), mainly in the most lateral cerebellar portions. The basal ganglia-induced effects were abolished upon section of the brachium pontis but not of the restiform body. Latency values of the responses, which were predominantly excitatory in nature, suggest the involvement of structures interposed between basal ganglia and precerebellar systems. We postulated that impulses issued by the basal ganglia could reach the cerebellum through a pathway that involves the pedunculopontine nucleus and the nucleus reticularis tegmenti pontis.

Animals↗
PubMed1986

Pyramidal input to the basal ganglia in the cat.

In cats with mesencephalic decerebration sparing the cerebral peduncles and ablation of sensorimotor cortex, changes in firing of single neurons of caudate nucleus (CD), putamen (PU), globus pallidus (GP) and entopeduncular necleus (EN) were studied following stimulation of the ipsilateral medullary pyramidal tract (MPT). Cells in CD and PU were not extensively influenced by impulses backfired from MPT (14.7% and 18.7%, respectively). Conversely, a larger number of GP cells (28.1%) and especially EN cells (46.9%) exhibited pronounced changes in their firing following MPT stimulation. The MPT-induced effects on CD and PU were either inhibition or excitations, the latter appearing at latencies greater than 11 ms. The responses observed in GP and EN cells were most frequently excitations, some of which appeared with latencies below 5 ms.

Afferent Pathways↗
PubMed1986

Influences on blink reflex induced by IA afferents in human subjects.

The effects induced by IA volleys, evoked with H reflex, on the blink reflex elicited upon electric activation of supraorbital nerves were investigated in 14 healthy subjects as well as in 4 cerebrovascular patients. In both groups a significant increase in amplitude of the early component (R1) of ipsilateral blink reflex has been observed. A brief discussion of possible neural systems which might be involved in these effects is given.

Blinking↗
PubMed1985

Influences of pyramidal tract on the subthalamic nucleus in the cat.

In adult cats, with mesencephalic decerebration sparing the cerebral peduncles and ablation of the sensorimotor cortex, changes in firing of single cells of subthalamic nucleus (STN) were analyzed upon stimulation of ipsilateral medullary pyramidal tract (PT). Twenty-two out of 44 of the STN cells exhibited, following PT stimulation, discharge changes that in the greatest part of cases (91%) were excitatory in nature. Excitations, always followed by inhibitory rebound, appeared with latency values compatible with a monosynaptic linkage.

Animals↗
PubMed1984

Altered time course of changes in the hippocampal concentration of excitatory and inhibitory amino acids during kainate-induced epilepsy.

The temporal sequence of electrophysiological and biochemical correlates of epilepsy induced by systemic injection of kainic acid (15 mg/kg i.p.) was investigated in male rats. A significant decrease in the hippocampal concentration of glutamate and aspartate was observed 20 min after the injection. These decreases preceded both electrographic and behavioral manifestations of epilepsy, thus suggesting a causal relationship between acidic amino acid changes and the genesis of kainate-induced hyperactivity. About 30-45 min after kainate injection, a decrease in glutamate, aspartate, glycine and taurine and no change in GABA concentration were observed. Bioelectrical activity, recorded in the regio inferior (CA3) of the hippocampus or in the fascia dentata revealed the presence of high frequency bursts separated by a long-lasting depression of discharge. About 55-75 min after the injection, the number of spikes in each burst increased and the duration and frequency of interictal pauses decreased. This stage was characterized by a decrease in glutamate and aspartate, restoration to normal of glutamine, glycine and taurine and a decrease in GABA.

Amino Acids↗
PubMed1983

Pyramidal influences on ventral thalamic nuclei in the cat.

In pericruciate cortex-ablated 'pyramidal cats', discharge changes in single neurons of ventral thalamic nuclei were studied, following stimulation of ipsilateral medullary (MPT) and contralateral cervical (CPT) pyramidal tract. It was seen that cells in ventrolateral nucleus, ventroanterior nucleus and ventromedial nucleus were not significantly (2.2%) modified by impulses coming from MPT and CPT. Conversely, a very high percentage (58.8%) of cells in ventrobasal complex (VB) responded to MPT stimulation (64.4% in ventroposterolateral nucleus, VPL, and 40.7% in ventroposteromedial nucleus, VPM). A considerable number (34.8%) of VPL cells responsive to MPT, were influenced by CPT, while none of the cells in VPM were. The most frequent effect observed in VB neurons, on MPT and CPT stimulation, was excitation followed by depression of discharge.

Animals↗
PubMed1983

Pyramidal input to the intracerebellar nuclei of the cat.

In unanesthetized cats it has been found that pyramidal volleys elicited upon medullary pyramidal tract stimulation were capable of modifying the discharge of 41% of intracerebellar nuclear cells, via pontocerebellar systems impinging predominantly on the lateral cerebellar cortex. The incidence of responsive cells was 80% in the dentate nucleus compared with 10% in the fastigial nucleus, 11% in the anterior and 12% in the posterior division of the interpositus nucleus. The response was in 59% of the cases excitation followed by inhibition, in 30% of the cases a pure excitation and in 11% of the cases a pure inhibition. Excitation, pure or followed by inhibition, had a mean latency of 5.78 ms and a mean duration of 12.21 ms, while inhibition displayed a mean latency of 9.03 ms and a mean duration of 34.64 ms. The possible functional significance of the pyramidal input to the lateral cerebellum is briefly discussed in relation to a possible convergence of pyramidal and associative impulses in single cerebellar neurons.

Animals↗
PubMed1982

Motor responses evoked by microstimulation of cerebellar interpositus nucleus in cats submitted to dorsal rhizotomy.

In cats with C4-T2 unilateral dorsal rhizotomy, stimulation of interpositus nucleus of the cerebellum, ipsilateral to the deafferented side, elicits in forelimbs single muscle contractions, which display threshold, latencies and spatial-temporal characteristics similar to those of the muscular responses produced in the other forelimb, upon stimulation of interpositus nucleus of the intact side. Motor effects induced by the interpositus nucleus-stimulation on the deafferented side disappear following red nucleus lesions. Single muscle contractions triggered from interpositus nucleus are, therefore, mediated by impulses impinging on alpha-motoneurons, via the rubrospinal pathway.

Afferent Pathways↗
PubMed1982

Interpositus nucleus influences on pyramidal tract neurons in the cat.

The influences of the interpositus nucleus on pyramidal tract neurons were investigated by stimulating, in unanesthetized cats, interpositus nucleus foci which activated single muscles in limbs, while recording unitary discharges of pyramidal tract neurons located in foci (area 4 gamma) from which contraction was obtained in the same muscles as those excited from interpositus nucleus (agonist pyramidal tract neurons), in their antagonist (antagonist pyramidal tract neurons), or in heteronymous muscles (heteronymous pyramidal tract neurons). It was found that agonist pyramidal tract neurons were inhibited from the interpositus nucleus, whereas antagonist pyramidal tract neurons displayed a pure excitatory or an excitatory-inhibitory pattern, and the heteronymous neurons were not significantly influenced. A direct activation of interposito-thalamic efferents could be responsible for these effects. In fact, unitary discharge changes of pyramidal tract neurons, elicited from interpositus nucleus stimulation, persisted after chronic intermediate cortex ablation and dentate nucleus lesions, and disappeared following coagulations in the ventrolateral nucleus of the thalamus. These results suggest that interpositus nucleus efferents, which activate a given muscle, via the rubrospinal pathway, could inhibit the discharge of pyramidal neurons controlling that muscle, via collaterals direct to the thalamic ventrolateral nucleus.

Animals↗