Biomedical subjects

V Perciavalle

Publications and source records attributed to V Perciavalle.

At least 37 records · Page 2Linked to original sources

PubMed1996

c-fos expression in the accessory oculomotor nuclei following neocerebellar stimulation.

The present study was carried out to determine whether, in the rat, the electric activation of the projection from the cerebellar lateral nucleus (LN) to the accessory oculomotor nuclei (AON; nucleus of posterior commissure, nucleus of Darkschewitsch, interstitial nucleus of Cajal) is capable of inducing c-fos expression. In particular, we compared the effects of a continuous LN stimulation at low-frequency (tonic stimulation) with those induced by high frequency pulse trains (phasic stimulation). The observed results show that the stimulation of LN induces c-fos expression in a significant proportion of neurones in the contralateral AON. Phasic stimulation was slightly more effective than tonic stimulation in producing c-fos expression.

Analysis of Variance↗

PubMed1996

The projections of the retrorubral field A8 to the hippocampal formation in the rat.

The dopaminergic neurons in the midbrain of the rat are located in three groups: the ventral tegmental area (VTA-A10), substantia nigra (SN-A9), and retrorubral field (RRF-A8). We have recently examined the organization of the projections from the VTA and the SN to the hippocampal formation (HF) in the rat. In the present study we characterize the projections of the RRF to the HF by using anterograde tracing, retrograde tracers, and tyrosine hydroxylase (TH) immunohistochemistry. Following iontophoretical injections of Phaseolous vulgaris leucoagglutinin (PHA-L) into the RRF, anterograde labeling was observed primarily in the ipsilateral subiculum and adjacent CA1 cell field. Sparse labeling was also observed in the CA3 cell field and dentate gyrus. The distribution of RRF neurons projecting to the HF was examined by injecting retrograde fluorescent tracers (fluorogold, fast blue, and nuclear yellow) into several hippocampal areas. The retrograde tracer findings indicate that the medial aspects of the RRF project to the subiculum and adjacent CA1 cell field of both the septal and temporal HF. In order to evaluate the percentage of dopaminergic cells of the RRF projecting to the HF, the retrograde neuronal tracer fluorogold was used in combination with TH immunohistochemistry. The quantitative evaluation of retrograde labeled and TH-immunoreactive (IR) cells showed that RRF projections to the HF are partially (10-18%) dopaminergic. The findings suggest that the general pattern of distribution and organization of the RRF-A8 projections to the HF is similar to that observed in our previous studies examining hippocampal afferents from the VTA and SN. The data also suggest a crude topographical organization of RRF afferents to the HF and a more prominent input to the temporal than to the septal HF.

Amidines↗

PubMed1996

Influences exerted by the frontal eye field on accessory oculomotor nuclei neurons of the rat.

The medial agranular cortex (AGm), considered the rat's analogous to the frontal eye fields of the monkey, sends a conspicuous projection towards the accessory oculomotor nuclei (AON), i.e. the nucleus of posterior commissure (NPC), the nucleus of Darkschewitsch (NDK) and the interstitial nucleus of Cajal (INC). The nature of the synaptic influences exerted by AGm on the AON neurons and the receptor(s) which mediates these cortical-evoked effects were studied in adult rats. Electrical stimulation of a single site within the AGm elicited changes in firing rate of a significant fraction of cells belonging to the ipsilateral accessory oculomotor nuclei (50% in INC, 52.3% in NDK and 52% in NPC). In the 82.9% of cases, the responses were excitations, most of which having latencies and response characteristics compatible with a monosynaptic linkage. The remaining 17.1% of cases were inhibitions with latencies ranging between 4 and 11 ms. Extracellular field potential recordings within the accessory oculomotor nuclei were interpreted as arising from impulses propagating along excitatory axons projecting in a bundle from the cortex. Effects of exogenously applied excitatory amino acid N-methyl-D-aspartate (NMDA) receptor antagonist 2-amino-5-phosphonovaleric acid (2APV) and of selective non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) were examined on synaptic excitation. Monosynaptic excitations induced by the cortical stimulation were abolished by microiontophoretic application of 2APV and not of DNQX. This finding indicates that cortical inputs activate specifically NMDA receptors of AON neurons.

2-Amino-5-phosphonovalerate↗

PubMed1995

Correlated activity in the spinocerebellum is related to spinal timing generators.

Encoding of information by neuronal populations implies a correlation of neural activity across cells. Therefore recent evidence for correlated activity in different parts of the nervous system has been interpreted as a possible mechanism for functional coupling or coordinated information processing. We compared the activity in the mossy fiber projection, the dorsal spinocerebellar tract (DSCT) with the responses of Purkinje cells in the spinocerebellum for evidence of correlated activity. A principal component analysis of post-stimulus spike activity revealed temporal patterns of correlated Purkinje cell activity in all parts of the spinocerebellum evoked by rapid, small amplitude passive joint rotations in anesthetized cats. The same basic temporal patterns were induced in DSCT neurons by joint rotations and also by direct nerve stimulation, showing that the patterning resulted from centrally generated rather than peripheral timing. The evidence implies that spinal timing generators, activated by mechanical stimulation of the ipsilateral hindlimb, transmit temporally correlated activity to the cerebellum via spinocerebellar pathways resulting in a coherent modulation of activity in diverse areas of the cerebellar cortex thereby providing the basis for a functional coupling.

Animals↗

PubMed1994

Projections from the cerebral cortex to the accessory oculomotor nuclei of the rat: a neuroanatomical and immunohistochemical study.

The projections from the cerebral cortex to the accessory oculomotor nuclei, i.e. the nucleus of posterior commissure (NPC), the nucleus of Darkschewitsch (NDK) and the interstitial nucleus of Cajal (INC) and the putative neurotransmitters subserving this pathway have been studied in adult rats. Retrograde labeling with Fluoro-Gold showed that only the more medial part of the agranular cortex, which is considered the rat's analogous to the frontal eye fields of the monkey, sends axon to the ipsilateral accessory oculomotor nuclei. The retrogradely-labeled cells were located primarily in the fifth layer of this cortical region. Following an injection of horseradish peroxidase conjugated with wheat germ agglutinin in this cortical area, we observed corticofugal labeled fibers reaching the accessory oculomotor nuclei and terminating as a fine dust-like terminal labeling in the NDK, in the dorso-lateral division of the INC and in the NPC, as well as in the medial oculomotor accessory nucleus, the red nucleus, the superior colliculus and, even though to a lesser extent, in the mesencephalic reticular formation and the central gray. With regard to the immunohistochemical approach, we observed that all the cells retrogradely labeled from the accessory oculomotor area were also stained by using glutamate or aspartate antisera.

Animals↗

PubMed1994

Non-N-methyl-D-aspartate receptors mediate neocerebellar excitation at accessory oculomotor nuclei synapses of the rat.

The nature of the receptor which mediates cerebellar-evoked monosynaptic excitations recorded from the accessory oculomotor nuclei (AON), i.e. the nucleus of posterior commissure, the nucleus of Darkschewitsch and the interstitial nucleus of Cajal, was studied in adult rats. Effects of exogenously applied excitatory amino acid (EAA) agonists N-methyl-D-aspartate (NMDA) and quisqualate (QUIS) and of selective NMDA receptor antagonist 2-amino-5-phosphonovaleric acid (2APV) and non-NMDA receptor antagonist 6,7-dinitroquinoxaline-2,3-dione (DNQX) were examined on both amino acid induced and synaptic excitation. Microiontophoretic application of NMDA and QUIS in the AON of the rat increases the neuronal discharge in a dose-dependent manner. These findings suggest that in the rat cells belonging to AON bear both NMDA and non-NMDA receptors. This result was confirmed by the fact that applications of 2APV selectively antagonized NMDA-induced responses without affecting those to QUIS, while DNQX blocked specifically the excitatory responses to QUIS and did not affect NMDA-mediated excitations. We did not observe any difference, between rats anesthetized with urethane and those anesthetized with halothane, with respect to capability of EAA agonists NMDA and QUIS to increase the AON cells activity and of EAA receptor antagonists 2APV and DNQX to abolish the NMDA-induced and the QUIS-induced effects, respectively. In addition, monosynaptic excitations induced by the stimulation of cerebellar lateral nucleus were abolished by microiontophoretic application of DNQX, but not of 2APV. This finding indicates that neocerebellar inputs activate specifically non-NMDA receptors of AON neurons.

Action Potentials↗

PubMed1993

Cerebellar influences on accessory oculomotor nuclei of the rat: a neuroanatomical, immunohistochemical, and electrophysiological study.

With the aim to evaluate a possible neocerebellar control on eye movements, the projections from the cerebellar lateral nucleus (LN) to the accessory oculomotor nuclei (i.e., the nucleus of posterior commissure, the nucleus of Darkschewitsch, and the interstitial nucleus of Cajal), the putative neurotransmitters subserving this pathway, and the nature of the synaptic influences exerted by these projections were studied in adult rats. We used the orthograde transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) to identify the mesencephalic areas where cerebellofugal fibers terminate, and retrograde labeling with the fluorescent dye fluoro-gold to estimate the incidence of cerebellar neurons projecting to the accessory oculomotor nuclei. Orthograde labeling showed that only a small contingent of cerebellofugal fibers reaches the contralateral accessory oculomotor nuclei. The retrogradely labeled cells were located primarily in the small-celled part of LN. By immunohistochemistry, we observed that all the cells retrogradely labeled from the accessory oculomotor area were also stained by using glutamate or aspartate antisera, but none of them were double-stained with a GABA antiserum. Electrical stimulation of the contralateral LN elicited changes in firing rate of a significant fraction of cells belonging to the accessory oculomotor nuclei (36.4% in the nucleus of posterior commissure, 47.1% in the nucleus of Darkschewitsch, and 44.6% in the interstitial nucleus of Cajal). In 57.8% of the cases, the responses were excitations, most of which had latencies and response characteristics compatible with a monosynaptic linkage. The remaining 42.2% of the cases were inhibitions with latencies ranging between 5 and 22 ms. Extracellular field potential recordings within the contralateral accessory oculomotor nuclei were interpreted as arising from impulses propagating along excitatory axons projecting in a bundle from the cerebellum. Stimulation of LN area in rats following intranuclear injection of kainic acid was not capable of evoking short latency excitations, so these responses can be considered to depend on the activation of LN efferents. The LN projection on accessory oculomotor nuclei could be part of the final precise control exerted by the neocerebellum on those brain structures concerned with movements of the eyes.

Animals↗

PubMed1993

Sensory responses to passive hindlimb joint rotation in the cerebellar cortex of the cat.

We recorded from Purkinje cells in the anterior and posterior lobes of the cerebellar vermis in anesthetized cats during passive flexion and extension of the ipsilateral hind foot. Nearly 60% of the 302 cells recorded in lobules I-IV anterior and VII-IX posterior responded to this stimulus. In lobule V, generally considered to be the forelimb projection area, about a third of the 38 cells tested responded to hind foot movement. Cells in the anterior lobe typically exhibited different poststimulus patterns in response to foot flexion and extension while posterior cells usually had the same response to these stimuli. We also noted that cells recorded in the medial vermis (within 2.7 mm of the midline) generally had longer response latencies than cells recorded more laterally (2.7 mm of the midline) generally had longer response latencies than cells recorded more laterally (2.7-4.5 mm) in both lobes. The results illustrate a diffuse proprioceptive input to the cerebellar vermis which has different features in various cerebellar areas.

Animals↗

PubMed1991

The cerebellopontine system: an electrophysiological study in the rat.

We examined the effects of electric stimulation of the cerebellar lateral nucleus (LN) in the rat on the activity of single pontocerebellar neurons in the basilar pontine nuclei (BPN) and the reticulotegmental nucleus (RtTg). We found that about half of the cells of these nuclei that were influenced by LN stimulation were inhibited. A significant fraction of both excitatory and inhibitory responses had latencies of less than 4 ms and were able to follow high frequency stimulation, compatible with a monosynaptic linkage. Extracellular field potential recordings within the BPN and RtTg were interpreted as arising from impulses propagating along inhibitory axons projecting in a bundle from the cerebellum to these pontine structures. Microiontophoretic administration of GABA antagonists bicuculline or picrotoxin abolished or attenuated most inhibitory effects. Therefore, we conclude that LN-induced inhibition is most likely mediated by cerebellopontine GABAergic fibers. The functional significance of this cerebellopontine inhibitory circuit is discussed.

Animals↗

PubMed1991

Origin of cuneate projections to the anterior and posterior lobes of the rat cerebellum.

The present study was carried out to analyze the topography of projections from external cuneate nucleus to the anterior and posterior lobes of the cerebellum and to investigate whether projections to the two lobes come from different cuneocerebellar neurons or from branching axons of the same cells. We used retrograde double-labeling techniques to estimate the incidence of cuneocerebellar neurons projecting to both anterior and posterior lobes via axon collaterals. Cells sending their axons to the lobus anterior were about twice the number of those projecting to the posterior lobe. The double-labeled cells were about 1/7 of all labeled neurons and were located mainly in the more lateral half of the nucleus. Therefore, the two lobes of the cerebellum are likely to receive common information from these cells, but different information from the separate populations of cuneocerebellar neurons that project only to one lobe or the other.

Animals↗

PubMed1991

Origin of spinal projections to the anterior and posterior lobes of the rat cerebellum.

The present study was carried out to analyze the topography of spinal projections to the anterior and posterior lobes of the cerebellum and to investigate whether projections to the two lobes come from different spinocerebellar neurons or from branching axons of the same cells. We used orthograde transport of horseradish peroxidase conjugated with wheat germ agglutinin (WGA-HRP) to identify the cerebellar areas where spinocerebellar axons terminate and retrograde double-labeling techniques to estimate the incidence of spinocerebellar neurons projecting to both anterior and posterior lobes via axon collaterals. Orthograde labeling confirmed that the rat, like other mammalian species, has spinocerebellar projections to two different regions of cerebellar cortex, i.e., lobules I-V of the anterior lobe and lobule VIII of the posterior lobe, with the highest incidence in lobules II, III, and VIII. We did not observe a clear difference in the distribution of afferents coming from different spinal segments to either of the two lobes. The double-labeled cells were located primarily in the lower thoracic and upper lumbar segments, almost exclusively in Clarke's column and in the dorso-lateral part of lamina 7 (in the region of the spinal border cells). It is likely that most or all of the spinocerebellar neurons in these structures project to both anterior and posterior lobes. Therefore, the two lobes of the cerebellum are likely to receive common information from these cells, but different information from the separate populations of spinocerebellar neurons that project only to one lobe or the other.

Afferent Pathways↗

PubMed1990

Differences in H-reflex between athletes trained for explosive contractions and non-trained subjects.

The efficacy of type Ia synapse on alpha-motoneurons of soleus and lateral gastrocnemius muscles has been investigated, using the H-reflex technique, in athletes engaged in sports requiring very rapid and intense contractions (sprinters and volley-ball players) as well as in non-trained subjects. It has been observed, in both muscles, that the ratio between the mean value of the maximal reflex response (Hmax) and the mean value of the maximal direct response (Mmax) elicited upon electrical stimulation of the tibial nerve is significantly smaller in athletes trained for explosive-type movements than in non-trained subjects. This difference in the Hmax: Mmax ratio was dependent on a smaller amplitude of Hmax and not on a greater amplitude of Mmax. No significant differences were observed between sprinters and volley-ball players. In both trained and non-trained subjects, soleus and lateral gastrocnemius muscles displayed significant differences in Hmax: Mmax ratio and Mmax amplitude but not in Hmax amplitude. Since the H-response is considered to be due mainly to activation of the smallest motoneurons in the motoneuronal pools, the difference in Hmax amplitude and Hmax: Mmax ratio between athletes and non-trained subjects could have been dependent on a lower incidence of these motoneurons in the athletes. This is in accord with the mechanical needs of muscles during explosive-type power training. Although this difference may have been wholly determined genetically, the possibility is discussed as to whether the lower incidence in sprinters and volley-ball players of small motoneurons could have been related to a training-induced transformation of small and slow motoneurons into large and fast ones.

Adult↗

PubMed1990

[Modification of the blink reflex in hemidystonia].

With the aim of evaluating the excitability of the brain stem reflex centers, we studied the side-to-side differences in the EMG activity of the early and late components of the blink reflex, in subjects with unilateral dystonia without demonstrable brain lesions. We observed that both early and late responses of direct blink reflex were significantly higher in the affected side than in the contralateral one.

Blinking↗

PubMed1990

[Adaptation of motor nerve fibers to physical activity].

The effects induced by training on the H-reflex of soleus and lateral gastrocnemius muscles have been studied on 19 adult male volunteers; out of these, 10 were non-trained subjects and the remaining 9 were top level athletes engaged in sports requiring very rapid and intense contractions (sprinters and volley-ball players). It has been observed that the latency of the M response is significantly higher in the athletes than in the non-trained subjects. Instead, no significant differences were observed between these two groups, concerning the latency of H response. The increase of M response latency is likely due to a decrease of nerve conduction velocity in the terminal part of motor fibers. The possibility that this conduction speed decrease could be dependent on sprouting and/or terminal branching growth of the motor nerve ending is discussed.

Adolescent↗

PubMed1990

Unilateral enhancement of early and late blink reflex components in hemidystonia.

The side-to-side differences in the EMG activity of the early and late components of blink reflex, regarded as revealing the state of excitability of the brain stem reflex centers, have been analyzed in patients with unilateral dystonia without demonstrable brain lesions. It has been observed that both early and late responses of direct blink reflex were higher on the side affected by hemidystonia than on the contralateral one, while the latency values were in the normal range. Possibility that an abnormal output from the striatum towards the brainstem structures involved in blink reflex appears on the affected side of hemidystonic patients is discussed.

Adult↗

PubMed1989

Projections from the intracerebellar nuclei to the ventral midbrain tegmentum in the rat.

The present study was undertaken to provide anatomical evidence, in the rat, for a direct projection from the cerebellum towards structures, other than the red nucleus, which belong to the ventral midbrain tegmentum, by using the retrograde as well as the anterograde horseradish peroxidase transport method. Following unilateral injection in the ventral midbrain tegmentum of horseradish peroxidase, free or conjugated to wheat germ agglutinin, sparing the red nucleus, retrogradely labeled neurons were found in the contralateral cerebellar lateral nucleus and, at lower density, in the interpositus nucleus. No labeled neurons were found in the fastigial nucleus of either side. Anterogradely labeled axons from lectin coupled horseradish peroxidase injection sites in the lateral and interpositus nuclei reached the contralateral ventral midbrain tegmentum. Terminal labeling was observed in the entire red nucleus as well as in the lateral division of the ventral tegmental area of Tsai, in the dorsal region of the substantia nigra pars compacta, and in the medial part of the retrorubral field. No terminal labeling was found in the caudal linear nucleus, interfascicular nucleus, peripeduncular nucleus, rostral linear nucleus of the raphe, substantia nigra pars lateralis and the substantia nigra pars reticulata. Terminal labeling was also not observed in the ventral midbrain tegmentum following horseradish peroxidase injection in lateral and interpositus nuclei of rats pretreated with kainic acid. In conclusion, it is noteworthy that, besides the red nucleus, the sole structures of ventral midbrain tegmentum receiving cerebellar efferents are those with a higher density of dopaminergic cells.

Animals↗

PubMed1988

Interleukin 2 modifies the bioelectric activity of some neurosecretory nuclei in the rat hypothalamus.

Introduction of 15-30 U of interleukin-2 (IL-2) into the 3rd ventricle of Wistar rats was followed by a marked and significant decrease in neuron discharge frequency in the ventromedial nucleus of hypothalamus and a marked increase in the supraoptic and paraventricular nuclei. The monoclonal antibody ART62 partly blocked these effects. The conventional anti-IL-2 receptor monoclonal antibody ART18 had only a non-significant influence on the effects of IL-2. Since the supraoptic and paraventricular nuclei secrete the antidiuretic hormone, their excitation may offer a partial explanation of the considerable water retention observed during IL-2 therapy against neoplasia.

Action Potentials↗

PubMed1988

Influences of dopaminergic systems on the blink reflex.

The effect of the anti-dopaminergic drug haloperidol (6 mg/day i.m. for 2 days) on the blink reflex elicited by electric stimulation of supraorbital nerves was investigated in 12 adult volunteers. A significant increase in amplitude of the early component (R1) of the reflex was observed. This increase disappeared within 5 days of stopping the drug. Possible neural systems which might be involved in these effects are considered.

Adult↗