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Biomedical subjects

G Amato

Publications and source records attributed to G Amato.

At least 109 records · Page 6Linked to original sources
PubMed1990

Effect of claustrum stimulation on neurons of the contralateral medial oculomotor area, in the cat.

In chloralose-anaesthetized cats, the extracellular spontaneous unitary activity was recorded from 157 neurons, located in the medial oculomotor area. 98 units were identified as projecting onto the superior colliculus. Electrical stimulations of the contralateral claustrum provoked, on 13 of these cells, an excitatory effect, lasting 10-35 ms and appearing with a latency of 20-50 ms. Full length section of the corpus callosum totally abolished the contralateral claustrum effect. The results suggest that in the cat, the claustrum may have a role in the bilateral control of the visuo-motor performance.

Animals↗
PubMed1990

Thioridazine chronic administration: a behavioural and autoradiographic study.

In rats the effects of chronic treatment with thioridazine (5 mg/kg orally administered for 22 days) were studied by means of behavioural supersensitivity to apomorphine and by means of dopamine (DA) receptors quantitative autoradiography. Locomotion and stereotypies induced by apomorphine increased after thioridazine chronic administration, whereas grooming behaviour decreased. Autoradiographic data showed an increase in DA receptors density both in the striatum and in the olfactory tubercle, to which the increase in stereotypies and locomotion could be respectively attributed. DA receptors increased also in the medial and dorsal frontal cortex. Moreover a decrease in DA receptors density appeared in the nucleus accumbens septi and in the lateral frontal cortex. Receptors decrease found in these regions might be associated with thioridazine-induced chronic inactivation of A10 DA neurons, to which the antipsychotic effect of the drug is attributed.

Animals↗
PubMed1990

Chronic thioridazine treatment differently affects DA receptors in striatum and in mesolimbo-cortical systems.

Chronic thioridazine administration (5 mg/kg for 22 days) caused both behavioral and dopamine (DA) receptor modifications in rats. After chronic thioridazine administration, a significant increase in both locomotion and stereotypies induced by apomorphine was observed. In particular, only sniffing increased significantly, whereas grooming behavior decreased and the number of rearings did not change. Autoradiographic data were consistent with the behavioral results. Chronic thioridazine caused an up-regulation of DA receptors both in the striatum and in the olfactory tubercle (O.T.). The striatal effect may account for the increase of stereotypies, whereas the effect in the olfactory tubercle may account for the increase in locomotion. An increase in DA receptors was also found in the medial (MCTX) and dorsal cortex (DCTX). However, a decrease in DA receptors appeared in the nucleus accumbens septi (NAS) and in the lateral cortex (LCTX). This decrease, selectively localized in the mesolimbic DA system, may represent the neurobiological substrate of the depolarization block observed in A10 neurons after chronic thioridazine treatment.

Animals↗
PubMed1990

[Correlations between vocal qualities and mental retardation].

This research is intended to verify the existence of vocal spectrographic alterations, with particular reference to the values of Fundamental Frequency, in patients with different levels of Mental Retardation. The results show the existence of a direct correspondence between the values of the Fundamental Frequency and the level of Mental Retardation: the spectrographic characteristics appear to be more altered in subjects with severe Mental Retardation. The spectrographics patterns are characterized by the presence of bi-phonation particularly at the onset time and at the end, and by a noise signal on constant frequency. The shifts of Fundamental Frequency and voice breakage are rarely detected.

Adolescent↗
PubMed1989

Effect of claustrum activation on the spontaneous unitary activity of frontal eye field neurons in the cat.

The influence of claustrum stimulation on spontaneous unitary activity of the ipsilateral frontal oculomotor area was analyzed in anesthetized cats. Sixty-five neurons were isolated, 37 of which (57%) were identified as projecting to the superior colliculus; on 12 of these last units (32%), electrical activation of the dorsal claustrum provoked an excitatory effect, which appeared after a latency of 5-15 ms and lasted 10-25 ms. These data could suggest the involvement of the claustrum in the visuomotor coordination function.

Action Potentials↗
PubMed1989

Circling behavior: ethological analysis and functional considerations.

Head-turning and circling movements evoked by substantia nigra (pars compacta) (SNpc) stimulation have been ethologically analyzed in order to attribute a functional meaning to these lateralization processes. It has been shown that these motor acts, separated by a constant interval, may be considered a fixed action pattern. The duration of the single acts depends on the SNpc stimulation parameters: the increase in the stimulus strength produces an increase in the number of turns but does not induce the disappearance of the orientation movement. The body movement is always preceded by the head-movement. Haloperidol administration induces a dose-related increase of the orientation component of the motor pattern. These data together with others in the literature suggest the participation of the SNpc in the mechanism of shift in the focus of attention from one point to another in the contralateral surrounding environment.

Animals↗
PubMed1989

The influence of dopaminergic A10 neurons on the motor pattern evoked by substantia nigra (pars compacta) stimulation.

The influence of the mesolimbic-mesocortical dopaminergic (DA) system on the motor pattern evoked by substantia nigra pars compacta (SNpc) stimulation was studied. Electrical stimulation of the A10 group of neurons caused an inhibitory effect preferentially directed towards the orientation movement. Sulpiride administration at low dosages (50 mg/kg i.p.) did not modify this movement at the basal condition, but abolished the increase of its duration induced by ventral tegmental area (VTA) co-stimulation. Mesolimbic activation opposes the effects of SNpc stimulation, restraining the animal in its antero-posterior axis by means of orientation movement inhibition. The results suggest a role of the DA mesolimbic-mesocortical system in the maintenance of focused attention.

Animals↗
PubMed1989

Claustral influence on ipsi- and contralateral motor cortical areas, in the cat.

The electrophysiological relationships between the claustrum and the contralateral motor areas of the cerebral cortex were studied in anaesthetized cats. The extracellular unitary activity of 207 pyramidal tract neurons (PTNs) was recorded from area 4 (125 cells) and area 6 (82 cells). Single shock activation of the contralateral claustrum affected 26% of the total tested PTNs, causing long lasting inhibition (44 PTNs) or long lasting inhibition preceded by early excitation (10 PTNs). Forty-three neurons of the 54 were also influenced by ipsilateral claustrum stimulation. Surgical removal of motor and insular cortices ipsilateral to the stimulated claustrum did not modify claustrum inhibition on contralateral PTNs, whereas section of the corpus callosum abolished this effect, suggesting the existence of a direct claustro-contralateral motor cortex pathway passing through the corpus callosum. These results support the hypothesis that the claustrum may exert a bilateral control on motor coordination.

Animals↗
PubMed1988

Facilitatory effect of ventral tegmental area A10 region on the attack behaviour in the cat: possible dopaminergic role in selective attention.

Lateral hypothalamus (LH) stimulation in cats which do not spontaneously attack rats, produces an attack pattern which may be divided into 3 main stages: the first, defined as exploratory time (ET), begins with an environmental search and culminates in orienting towards the prey; in the second, defined as attack time (AT), the cat stalks the rat; the last is the biting stage in which the cat seizes and kills the prey by biting its head and neck. The effects of ventral tegmental area (VTA) stimulation on the latency of the whole sequence and on the different stages of the attack pattern were studied. VTA activation resulted in a significant decrease of biting latency, due to the reduction of exploratory time. Moreover, a significant period of prey fixation, seldom present during LH stimulation alone, was observed after VTA-LH co-stimulation. Sulpiride injection caused the disappearance of VTA effects on the predatory pattern. The results indicate that VTA activation induces a decrease in behaviour related to exploration of the environment, and an increase in the focusing of attention on the prey, which seems an important component in the regulation of the predatory pattern. Pharmacological evidence indicates that the VTA effect is mediated by the mesolimbic-mesocortical dopaminergic (DA) system.

Animals↗
PubMed1988

Evaluation of in vitro activity of teicoplanin against recent clinical isolates.

The in vitro antibacterial activity of teicoplanin, a new glycopeptide antibiotic, previously named teichomycin A2, has been compared to that of five other chemoantibiotics: netilmicin, clindamycin, rifampicin, enoxacin and vancomycin. The minimum inhibitory concentration (MIC) values against 588 gram-positive strains, 561 facultative aerobes and 27 anaerobes, recently isolated from clinical specimens, were evaluated. Teicoplanin showed the highest activity against all the tested strains, with a geometrical mean of the MICs (GMM), a MIC50 and MIC90 of 0.123, 0.12 and 0.5 micrograms/ml respectively.

Anti-Bacterial Agents↗
PubMed1987

Inhibitory effect of the ventral tegmental A10 region on the hypothalamic defence reaction: evidence for a possible dopaminergic mediation.

The influence of A10 region neurons of the ventral tegmental area (VTA) on the defence reaction evoked by stimulation of the ventromedial hypothalamic nucleus (VMH) was studied in the cat. The latency of the hissing in the defence reaction increased when the VTA was stimulated both ipsi- and contralaterally. A sulpiride (50mg/kg i.p.) injection totally abolished the VTA-provoked increase of the hissing latency without affecting the basal response.

Animals↗
PubMed1987

Electrophysiological relationship between claustrum and contralateral area 4 and 6 pyramidal tract neurons.

The connections between the claustrum and the contralateral motor areas were electrophysiologically investigated in cats under chloralose anesthesia. The extracellular unitary activity of 81 pyramidal tract neurons (PTNs) was recorded; 22 PTNs were inhibited by activation of the contralateral claustrum; inhibition was preceded by an early activation of 4 out of the 22 inhibited PTNs. Section of the corpus callosum abolished the contralateral claustrum effect, while the action of the ipsilateral homologous structure persisted.

Animals↗