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Biomedical subjects

L Petrosini

Publications and source records attributed to L Petrosini.

At least 37 records · Page 2Linked to original sources
PubMed1993

Hemicerebellectomy and motor behaviour in rats. III. Kinematics of recovered spontaneous locomotion after lesions at different developmental stages.

The locomotion of rats with a right hemicerebellectomy (HCb) performed in adulthood was compared by means of kinematic analysis with the locomotion of rats with a similar lesion performed on the first postnatal day. The age at which the animals received cerebellar lesion made a significant difference with respect to the locomotor strategies utilized in adulthood. During stance, neonatal operate rats showed a clear hyperextension of both hindlimbs but not of the forelimbs. Their locomotor posture was characterized by spinal flexion with the head held lower than normal. During swing, they showed a tendency towards 'high stepping'. Their steps were regular and symmetrical but hypometric. Adult lesioned animals displayed a marked extensor hypotonia, ipsilateral to the lesion during stance and a relevant hyperflexion affecting both sides, during swing. Alteration of the interlimb coordination and modified sequence of steps were also observed. Thus, a highly asymmetrical, impaired and unstable locomotion was displayed by this group of animals. The present findings demonstrate the importance of the age-at-lesion factor in determining the motor strategies in the recovery of locomotor function after HCb in the rat. This evidence is discussed in the light of the widespread anatomical remodelling already demonstrated following neonatal, but not adult, HCb in rats.

Aging↗
PubMed1993

Vestibular compensation is affected by treatment with dopamine active agents.

The aim of the present work was to examine the effects of postoperative treatments with agents active on dopaminergic system on vestibular recovery from the postural and ocular symptoms which follow a unilateral labyrinthectomy. Hemilabyrinthectomized guinea pigs were given a daily i.p. injection of bromocriptine (1 mg/kg) or sulpiride (10 mg/kg) or lisuride (0.1 mg/kg) or saline from post-operative days 1 to 21. Treatment with bromocriptine, a D2 agonist, accelerates compensation of postural and ocular symptoms. Conversely, treatment with sulpiride, a D2 antagonist, slows down the reachievement of symmetrical posture and stable ocular motility. Finally, the lisuride treatment, a drug active on D2 but also on other monoaminergic receptors, delays vestibular recovery so markedly to reach a "freezing" of vestibular deficits during drug treatment. These findings indicate that the already demonstrated role of dopamine in motor activity and learning can be extended to the learning processes required to recover from vestibular asymmetries.

Animals↗
PubMed1990

Hemicerebellectomy and motor behaviour in rats. I. Development of motor function after neonatal lesion.

This study was undertaken to determine the effect of a neonatal hemicerebellectomy (HCb) on the motor development of rats and to determine whether various aspects of motor behaviour were affected to a similar degree. Postnatal development of postural reflexes, locomotion and dynamic postural adjustments was examined during the first four months of life in normal and in neonatal HCbed rats. The results indicate that classes of motor responses are controlled by cerebellar networks to clearly different extents. Emergence of quadruped stance, placing reactions and swimming development were unaffected by neonatal cerebellar lesion. Righting reflexes, cliff avoidance and geotaxic reactions, pivoting and crawling all showed a delayed development although the subsequent recovery was almost complete. The complex postural adjustments required in crossing a narrow path or in suspending on a wire remained permanently impaired. Finally, some behaviours developed normally and only subsequently became defective. This "growing into a deficit" was displayed by the progressively reduced hindlimb grasping and the development of a vestibular drop response with a directional bias. An impressive finding was the shifting of postural asymmetries from the lesion side to the contralateral one occurring around the third postnatal week. These data providing a description of the effect of HCb on motor development are interpreted as indicating a progressive involvement of the archi- and neo-cerebellar structures in the motor function of the rat.

Animals↗
PubMed1990

Hemicerebellectomy and motor behaviour in rats. II. Effects of cerebellar lesion performed at different developmental stages.

Rats with a right hemicerebellectomy (HCb) performed in adulthood or at weaning were compared behaviourally to rats with a similar lesion performed on the first postnatal day. The age at which animals received cerebellar lesions made a significant difference with respect to the behavioural outcome in adulthood. Posture, locomotion and motor behaviour were analysed by a battery of sensorimotor tests. Behavioural measurements showed a clear relationship between age at surgery and behavioural effects; rats with neonatal cerebellar lesions showed a slight extensor hypotonia contralateral to the lesion side and efficient locomotor activity, while the adult operated group exhibited a severe extensor hypotonia ipsilateral to the lesion side and hampered locomotion characterized by a wide base and ataxia. Weanling operated rats displayed a symptomatology similar to that observed in adult operates, although less severe. In the postural dynamic adjustments which the sensorimotor tests required, the youngest operated animals obtained higher scores in comparison to the other two experimental groups, except for the lack of hindlimb usage in the suspension on a wire test. These results, which show the importance of the age-at-lesion factor for the recovery of motor function after HCb in the rat, are discussed in the light of the widespread anatomical reorganization already demonstrated following neonatal HCb in rats.

Aging↗
PubMed1987

Spontaneous eye motility following a unilateral vestibular lesion.

The strong imbalance of the output of vestibular nuclei, resulting from a hemilabyrinthectomy, causes among other postural and ocular symptoms, a failure to hold a steady ocular position in the dark. In this study the time course of the spontaneous eye motility following a right hemilabyrinthectomy was analyzed. In all animals, at the first recordings, drifts of 0.8-1.0 degrees/s were present. These drifts were directed to the lesion side, then they shifted their trajectory more than once. At the final recordings, most animals exhibited very slow drifts (0.05-0.1 degrees/s) directed to the intact side suggesting an overcompensation of the initial extreme rightward deviation.

Animals↗
PubMed1987

Behavioural recovery from unilateral vestibular lesion is facilitated by GM1 ganglioside treatment.

Exogenously administered gangliosides function in vivo to facilitate survival and repair of damaged neurones in both central and peripheral nervous systems. These effects have been attributed to their neuritogenic and neuronotrophic properties. In this investigation the effects of ganglioside treatment have been studied on the compensation that follows a unilateral labyrinthectomy, considering that the vestibular recovery is supposed to be achieved through a mechanism of sprouting acting on the deafferented neurones. Hemilabyrinthectomized guinea pigs were given a daily injection of either GM1 ganglioside (30 mg/kg, i.p.) or saline for 21 days. As regards postural symptoms, the GM1 group more quickly restored a posture of the head non-deviated in the horizontal plane, while the remaining postural symptomatology was not significantly affected by the treatment. Furthermore, the GM1-treated group attained more rapidly an ocular position characterized by very slow drifts (or by no drift at all), directed towards the side of the intact labyrinth. Ganglioside treatment did not reduce the severity of the initial hemilabyrinthectomy impairments and the effect of the treatment became evident with time. This result is consistent with the hypothesis that also in this model of neuronal plasticity, gangliosides act by enhancing reactive synaptogenesis on the deafferented vestibular neurones.

Afferent Pathways↗
PubMed1984

Tonic cervical influences on eye nystagmus following hemilabyrinthectomy: immediate and plastic effects.

In intact guinea pigs a passive horizontal rotation of the body about the fixed head induces compensatory ocular movements (cervico-ocular reflex). When the static neck deviation is maintained, a significant ocular displacement is observed. In acutely hemilabyrinthectomized animals, static body deviation towards the lesion side tonically alters eye nystagmus. It affects slow phase eye velocity and quick phase amplitude and frequency causing the eye to reach a less eccentric orbital position. Apart from such immediate influences, a plastic effect on eye nystagmus abatement is induced. In the animals restrained with no body-on-head deviation, abatement of nystagmus is delayed with respect to the animals restrained with 35 degrees body deviation towards the lesion side. Thus the head position signal is not only a contributing factor for the correction of postural deficits but also influences the time course of the ocular balancing process following unilateral vestibular damage.

Adaptation, Physiological↗
PubMed1984

Task-dependent rate of recovery from hemilabyrinthectomy: an analysis of swimming and locomotor performances.

Guinea pigs were hemilabyrinthectomized or hemicerebellectomized and repeatedly tested on a swimming task and in the open field. Initially, hemilabyrinthectomized animals showed impaired swimming behavior which improved over time: within 21-25 days after the vestibular damage, the animals were able to swim around the tank with coordinated motor patterns. Only a slight tendency to turn towards the lesion side continued to be displayed. Hemicerebellectomized guinea pigs were significantly less impaired in their swimming ability since the very first test session. Both groups of animals showed similar recovery time courses in their open field activity. The data demonstrate a task-dependence in the rate of recovery following a unilateral labyrinthectomy and a substantial contribution by the labyrinth to swimming function.

Adaptation, Physiological↗
PubMed1983

Compensation of vestibular symptoms in hemilabyrinthectomized guinea pigs. Role of the sensorimotor activation.

The effect of sensorimotor activation on compensatory rate of vestibular asymmetries after unilateral labyrinthectomy was analyzed in guinea pigs. An intensified sensorimotor activation was obtained by putting in water the animals immediately after the appearance of hemilabyrinthectomy (HL) symptoms. The water-maintained group exhibited a faster dampening of vestibular disturbances in comparison with control animals. Both ocular and postural asymmetries declined to about 50% of peak values after 2-3 h from HL, while in control group the same extent of recovery was achieved in 4-6 h from HL. It is concluded that the generalized activation of the ascending spinal pathways carrying exteroceptive and proprioceptive information to the vestibular nuclei represents a favourable condition for the regainment of ocular and postural balance impaired by HL.

Animals↗
PubMed1982

The effect of ethanol on early manifestations of recovery from vestibular lesion.

The effect of intraperitoneal (i.p.) injection of ethanol (250 mg/kg) on compensatory rate of vestibular symptoms after unilateral labyrinthectomy was studied in guinea pigs. The treated group showed a faster dampening of vestibular disturbances in comparison with control animals. Both ocular and postural asymmetries declined to at least 50% of peak values after 2-3 h following alcohol injection. In control animals the same extent of compensation was achieved in 5-8 h after saline injection. This accelerating action of ethanol on early manifestations of vestibular compensation can be obtained by means of an increased inhibitory influence on vestibular nuclei and of an increased information provided by sensory systems.

Afferent Pathways↗
PubMed1981

Role of vestibular nuclei in 'optic' nystagmus.

Horizontal eye nystagmus beating towards the stimulated side ('optic' nystagmus) was evoked in 25 guinea pigs by stimulating an optic nerve. The complete ablation of the vestibular nuclear complex abolished this nystagmus. In a second group of 15 animals, the behavior of 63 vestibular neurons identified electrophysiologically was analyzed during eye nystagmus; most of these neurons responded with a tonic increase in discharge rate to stimulation of the optic nerves. Units sensitive to the direction of optic and labyrinthine nystagmus were also identified.

Animals↗