Biomedical subjects

V Perciavalle

Publications and source records attributed to V Perciavalle.

At least 19 recordsLinked to original sources

PubMed2006

Spatial anisotropy in the encoding of three-dimensional passive limb position by the spinocerebellum.

In an earlier study, we found that the encoding of limb position in the sagittal plane across the population of spinocerebellar Purkinje cells was anisotropic with a preferential gradient along horizontal direction. The aim of this study was to extend to a three-dimensional (3D) workspace the analysis of the relationships between Purkinje cells activity and rat's forelimb spatial position. In anesthetized animals, the extracellular activity of 121 neurons was recorded while a robot passively placed the limb in 18 positions within a cubic workspace (3x3x3 cm). In order to characterize the relationship between spatial locations and Purkinje cell activity we performed a backward stepwise regression starting from a model with three independent variables representing the antero-posterior, the medial-lateral and the vertical axes of workspace. Regression analysis showed that the firing of most cells was modulated exclusively along the antero-posterior (25%) or the medial-lateral (38%) axis, while a small portion was related only to the vertical axis (8%), indicating a generalized nonuniform sensitivity of Purkinje cells to limb displacement in 3D space.

Action Potentials↗

PubMed2006

Control of head stability during gait initiation in young and older women.

Transition tasks between static and dynamic situations may challenge head stabilization and balance in older individuals. The study was designed to investigate differences between young and older women in the upper body motion during the voluntary task of gait initiation. Seven young (25+/-2.3 years) and seven older healthy women (78+/-3.4 years) were required to stand on a force platform and initiate walking at their self-selected preferred speed. Angles of head, neck and trunk were measured by motion analysis in the sagittal plane and a cross-correlation analysis was performed on segments pairs. Variability of head and neck angular displacements, as indicated by average standard deviation, was significantly greater in the older than in the young participants. The young women maintained dynamic stability of the upper body, as forward flexion of the trunk was consistently counteracted by coordinated head-neck extension. Differently, movement patterns employed by the older women also included a rigid motion of all upper body segments leaning forward as a single unit. These results demonstrated that older women perform the transition from standing to walking with greater variability in the patterns of upper body motion compared to young women.

Adult↗

PubMed2006

Blink reflex abnormalities in children with Tourette syndrome.

Tourette syndrome (TS) is a common disorder which typically occurs during childhood or early adolescence. There is no definitive diagnostic test for TS. The objective of this study was to demonstrate whether neurophysiological abnormalities of the blink reflex can be observed in children with TS. We enrolled 15 children with TS, diagnosed according to DSM IV Diagnostic Criteria, and 15 controls. The blink reflex was elicited by stimulating the supraorbital nerve in order to measure the early response (R1), homolateral and contralateral R2 (late) responses, amplitude of R1 and duration of R2. The mean duration of R2 was significantly longer in TS patients than in the controls (P < 0.001, Student's t-test). An abnormal pattern of the blink reflex can be, even in childhood, an early neurophysiologic marker of TS, which is not related to the duration of TS or to the age of onset.

Adolescent↗

PubMed2006

Organization of bilateral spinal projections to the lateral reticular nucleus of the rat.

The present study was carried out to analyze the topography of bilateral spinal projections to the lateral reticular nucleus (LRN). We used retrograde transport of fluorescent tracers Fast Blue and Diamidino Yellow to identify spinal neurons projecting to the ipsilateral and/or contralateral LRN, as well as orthograde transport of Phaseolus vulgaris leucoagglutinin to identify the LRN areas where spinoreticular axons terminate. Orthograde labeling confirmed that bilateral spinoreticular projections coming from cervical and upper-thoracic segments terminate in the magnocellular division of LRN, while those coming from the lower-thoracic, lumbar and sacral segments end in the parvocellular division of the nucleus; only a sparse spinal input has been observed in the subtrigeminal division of LRN. Retrograde labeling showed that labeled neurons were present at all spinal levels and in particular large numbers in the cervical and lumbar enlargements. Retrogradely single-labeled cells were located, with contralateral predominance, in all segments of the spinal cord, within laminae IV, V, VI, VIII, and X, whereas in laminae III and VII labeled neurons were mainly observed ipsilaterally. Furthermore, a small fraction of double-labeled cells (7.4%) was observed throughout the spinal cord, mainly in laminae III, IV, VII and VIII.

Animals↗

PubMed2003

Exercise increases cytochrome oxidase activity in specific cerebellar areas of the rat.

The purpose of this study was to determine whether or not chronic exercise could cause long-term metabolic plasticity in cerebellum. The activity of cytochrome oxidase (COX), coupled to ATP production, reflects long-term plasticity in metabolic capacity. The present study examined whether or not 10 weeks of voluntary exercise would increase COX activity in the cerebellum. Adult male Sprague-Dawley rats were randomly assigned to a control or exercise condition. Exercising rats had running wheels attached to their home cages. COX activity was measured using histochemical methods and optical densitometry. Rats in the exercise condition had significantly higher optical density in spinocerebellum (mainly in lobules 3, 4, 5, 8, 9 and in the copula), but not in neocerebellar crura I and II.

Animals↗

PubMed2001

Effects of cerebellar dentate nucleus GABAergic cells on rat inferior olivary neurons.

The present study was undertaken to analyze the effects on unitary activity of inferior olive (IO) neurons elicited by activation of cerebellar lateral nucleus (LN), in rats submitted to the chronic destruction of MDJ structures, i.e. in animals in which the LN-evoked effects in IO should be depended only on activation of GABAergic cells of LN. It has been observed that about two-thirds of the olivocerebellar neurons are significantly affected by LN stimulation, and > 68% of those cells were inhibited. Two-thirds of the inhibitory responses were compatible with a monosynaptic linkage, whereas the remaining inhibitions were probably due to polisynaptic linkages. The majority of LN-induced inhibitions was abolished or greatly reduced following application of GABA antagonists.

Action Potentials↗

PubMed2001

Reticulocerebellar projections to the anterior and posterior lobes of the rat cerebellum.

By using retrograde double-labeling techniques, we analyzed the topography of projections from the lateral reticular nucleus (LRN) to the anterior and posterior lobes of the cerebellum, with the aim to investigate whether LRN projections to the two lobes come from different neurons or from branching axons of the same cells. We observed that about 4/5 of afferents the cerebellar cortex come from the ipsilateral LRN and about 1/5 from the contralateral nucleus. Furthermore, magnocellular division of LRN projects mainly to the anterior lobe, whereas parvicellular part primarily to the posterior lobe. The double-labelled cells were very numerous (about 1/3) and were located throughout the LRN, with the higher incidence in the magnocellular division and the lower in the subtrigeminal part.

Animals↗

PubMed2001

Tiagabine treatment and DNA damage in rat astrocytes: an in vitro study by comet assay.

We studied in vitro the effects of Tiagabine on genomic DNA of cortical rat astrocytes. To evaluate DNA damage, we used a relatively simple technique called Single Cell Gel Electrophoresis or Comet assay. Tiagabine was dissolved in culture medium and added at concentration of 1, 10, 20 and 50 microg/ml on 12-day old cultured astrocytes. In presence of 1 and 10 microg/ml of Tiagabine, no DNA damage was observed after 48 h of treatment. A moderate DNA damage was instead observed for cells exposed to 20 microg/ml of antiepileptic drug. Finally, DNA fragmentation was more evident after treatment with 50 microg/ml of Tiagabine. We conclude that Tiagabine, at the usual recommended doses, does not appear to influence negatively the cortical rat astrocytes, inducing DNA fragmentation only at very high concentrations.

Animals↗

PubMed2001

Effects of Gabapentin and Topiramate in primary rat astrocyte cultures.

We studied in vitro the effects of anticonvulsant drugs Gabapentin and Topiramate on the production of reactive oxygen species and nitric oxide (NO), the activity of glutamine synthetase (GS), and cell viability in primary cultures of rat cortical astrocytes which are intimately involved in the normal functioning of neurons. We investigated the effects of these drugs at concentrations within the therapeutic range (1, 10 and 50 microg/ml). We observed that, in cultured astrocytes, Gabapentin induced a weak increase in the biosynthesis of NO, a mild decrease in GS activity and cell viability, and minor induction of a stress condition. Topiramate was observed to induce even greater stressor effects on these cells.

Acetates↗

PubMed2000

Biological effects of tiagabine on primary cortical astrocyte cultures of rat.

Biological effects of tiagabine, a new antiepileptic drug, were analyzed on cultures of rat's cortical astrocytes. Tiagabine was added to the cultures at concentrations of 1 and 10 microg/ml, correspondent to therapeutic range; cell viability (tetrazolium salt assay and lactic dehydrogenase release), maturation and differentiation (glutamine synthetase activity) and presence of stress conditions (reactive oxygen species formation, inducible nitric oxide synthetase expression and 70 kDa heath shock protein production) were tested. Our results indicate that the addition of Tiagabine to primary astrocytes not only did not change significantly the examined metabolic activities but also seems to exert a protective action against oxidative stress. Thus, our data reinforce the idea that Tiagabine may be considered an effective promising drug in the treatment of epilepsy.

Animals↗

PubMed2000

Sensory representation of passive movement kinematics by rat's spinocerebellar Purkinje cells.

In this paper we examined Purkinje cells' sensory representations of kinematic parameters of passive movements imposed to the forelimb of anesthetized rats. Simple spike Purkinje cell activity was recorded while the rat's ipsilateral forearm was moved passively along circular footpaths at two different speeds. We found that the activity of 35.33% (165/467) of the neurons was significantly modulated during movement cycles. A multivariate regression analysis indicated that movement direction was the predominant factor in determining Purkinje cell activity, whereas movement velocity (i.e. the combination of movement direction and speed) was represented to a much lesser degree. Based on this result, we might suggest that a cortical efferent copy is necessary to the cerebellum in order to elaborate a movement velocity signal.

Action Potentials↗

PubMed2000

Distribution of spinocerebellar Purkinje cell responses to passive forelimb movements in the rat.

We recorded Purkinje cell activity throughout the spinocerebellum of anaesthetized rats while imposing circular passive movements to the unrestrained forelimb. The aim was to understand the type of processing of sensory information occurring at the level of the cerebellar cortex, on the basis that precerebellar sensory neurons have been shown to represent whole limb movement parameters better than single joint movements. We observed that neurons representing sensory aspects of arm movements were scattered throughout the spinocerebellar cortex without a distinct segregation from those that did not respond, albeit the relative density of responsive and unresponsive neurons was quite variable and depended on the area of the cortex. Furthermore, Purkinje cells that responded significantly to the arm movement cycles all showed the same response pattern consisting of a firing rate increase during the downward extension of the arm. These results are discussed as suggesting a coordinate framework for the representation of proprioceptive information in the cerebellum congruent to that observed for encoding motor parameters.

Animals↗

PubMed2000

C-Fos expression in the basilar pontine nuclei and reticulotegmental nucleus of the rat following lateral cerebellar nucleus stimulation.

The present study was carried out with the aim to observe whether, in the rat, the electric activation of the projection form the cerebellar lateral nucleus (LN) to the basilar pontine nuclei (BPN) and to the reticulotegmental nucleus (RtTg) is capable to induce the 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 fraction of neurons in the contralateral BPN and RtTg. It was also observed that phasic stimulation was slightly more capable in producing c-Fos expression with respect to the tonic stimulation. Furthermore, systemic injection of MK-801, a non-competitive antagonist of the NMDA receptor, reduced the LN-induced c-Fos expression in BPN and RtTg. In contrast, GYKI 52466, an AMPA/kainate receptor antagonist, did not change the LN driven induction of c-Fos in both BPN and RtTg.

Animals↗

PubMed1999

Cortical control of cerebellar dentato-rubral and dentato-olivary neurons.

The cortical input of 117 dentate nucleus neurons projecting either to the red nucleus (73 cells) or to the inferior olive (44 units) was studied electrophysiologically in rats. The majority of cells in both groups responded to electrical stimulation of discrete sites of the contralateral motor cortex. However, activation latencies from the same cortical focus were shorter for neurons projecting to the red nucleus than for olivary-projecting neurons. Principal components analysis pointed out significant differences between the two neuronal subgroups also in the temporal pattern of activity. These results suggest that a motor command might be transmitted through parallel independent channels to cerebellar neurons projecting to different regions of the brainstem.

Animals↗

PubMed1999

On the relation of rat's external cuneate activity to global parameters of forelimb posture.

Using anesthetized adult rats, we studied the relationships between the activity of cells belonging to the external cuneate nucleus (ECN) and passive forelimb positions. In essence, we sought to distinguish between a representation of limb position based on local limb parameters (individual joint angles, for example) or a representation based on more global parameters such as the length and the orientation of the limb axis. Using multivariate regression analyses we found that most neurons showed strong linear relationships with the length and the orientation of the limb axis. Relationships to individual joint angles were, instead, rather weak and in most cases not significant. This result implies an extensive integration of sensory information at the level of second order sensory neurons.

Animals↗

PubMed1998

Spinocerebellar Purkinje cells and rat forelimb postures: a direction-dependent activity.

On anesthetized adult rats, we examined the possibility that the discharges of spinocerebellar Purkinje cells (PCs) are modulated by passive limb positioning. The rat forelimb was passively placed in four different sagittal positions while the simple spike spontaneous activity of single PCs was recorded; recordings started 5 s after the reaching of the posture and the forelimb remained at each position for at least 30 s. Although the activity of the PCs did not reflect the forelimb position, it showed hysteresis that depended in a cosine fashion on the direction of the preceding movement. This implies that the directional sensitivity of spinocerebellar PCs is persistent, since the activity levels were almost constant throughout the recording time.

Action Potentials↗

PubMed1998

Spatial organization of proprioception in the cat spinocerebellum. Purkinje cell responses to passive foot rotation.

This study examines the spinocerebellar locations of Purkinje cells that responded to passive foot rotations at the ankle joint in anaesthetized cats. Using a novel approach for mapping the locations of recorded cells from several animals onto an unfolded two-dimensional representation of the cortex, we found that cells distributed throughout the anterior-posterior extent of the spinocerebellar cortex, except in the most medial parts corresponding to zones a and b, were responsive to ankle joint rotation. The cell distributions revealed a clustering according to their response amplitudes, which showed evidence for both parasagittal and transverse banding.

Animals↗

PubMed1996

Effects of the retrorubral field stimulation on the excitability of the rat hippocampus in vivo.

We studied in vivo the influences exerted by the retrorubral field (RRF) on the on commissural-evoked CA1 pyramidal cell excitability in the rat hippocampal formation (HF). The stimulation of RRF before the activation of the contralateral CA3 area evoked in all the studied rats a reduction in amplitude of the evoked population spike in the CA1 pyramidal cell body layer of both the dorsal and the ventral HF. No significant differences in the intensity of the inhibitory effect were observed between dorsal and ventral parts of the HF. The stimulation of the ipsilateral RRF reduced the amplitude of the evoked population spike in a higher degree with respect to the contralateral side. Since these side-to-side differences were significant, it can be concluded that the RRF-induced inhibitory effect is stronger on the ipsilateral CA1 pyramidal cells. The inhibitory effect appears within 0.1 s of stimulating the RRF, reaches its maximal effect around 0.4-0.5 s following the conditioning train and returned to its control size after 5 s.

Animals↗