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Biomedical subjects

G F Ricci

Publications and source records attributed to G F Ricci.

17 recordsLinked to original sources
PubMed1995

Seizure susceptibility in immature rats with micrencephaly induced by prenatal exposure to methylazoxymethanol acetate.

The administration of the alkylating neurotoxin methylazoxymethanol acetate (MAM) to pregnant rats on day 15 of gestation induces, in the offspring, a marked micrencephaly, characterized by an impaired formation of interneurons at cortical, hippocampal and striatal levels. Since in man developmental CNS malformations are often associated with severe epileptogenic encephalopathies with seizures appearing in the first months or years of life, we have studied the development of kainic-acid- and bicuculline-induced seizures in 15- and 30-day-old rats, prenatally exposed to MAM. Compared to controls, a higher susceptibility to seizures has been found in micrencephalic rats aged 15 days, while no significant differences have been observed in those aged 30 days. It is hypothesized that the cerebral global anatomical dysgenesis caused by MAM underlies the higher seizure susceptibility shown by animals during the first periods of life. Successively, the processes of adjustment occurring between the cerebral regions affected by the neurotoxic action of MAM and the afferent and efferent pathways spared by the substance may re-establish adequate interneuronal relationships and, therefore, a normal convulsive susceptibility.

Age Factors↗
PubMed1988

EEG spectral analysis after minor head injury in man.

A quantitative EEG analysis was performed on the posterior lead of 18 patients with their eyes closed 3-10 days after minor head injury. There was a significant increase of the mean power of slow alpha (8-10 c/sec), a reduction of fast alpha (10.5-13.5 c/sec), with a shift of mean alpha frequency towards lower values, and a reduction of fast beta (20.5-36 c/sec) in the patients with head injuries compared with the age- and sex-matched patients in the control group. Therefore, power spectral EEG analysis performed with the above-mentioned criteria may be suggested as a sensitive tool to be added to others during the neurophysiological follow-up studies of people with head injuries.

Accidents, Traffic↗
PubMed1988

Effects of progabide on bicuculline-induced epileptic seizures in developing rats.

The effects of progabide, a direct gamma-aminobutyric acid (GABA) receptor agonist, on bicuculline-induced seizures have been tested in developing rats, ages 7-28 days, to study the correlation between the antiepileptic effectiveness of this drug and the level of functional maturation of the GABAergic system. The incidence, latency of appearance, and behavioral characteristics of the epileptic manifestations, their evolution toward status epilepticus, and the percentage of recovery from status epilepticus have been evaluated in rats that had received a single injection (treatment) or three successive daily administrations (pretreatment) of progabide. The results have been compared with those obtained in a control group of animals in which only bicuculline had been injected. In rats ages 7-14 days the treatment appears to be substantially ineffective in protecting animals against bicuculline seizures and their consequences, probably because of the substantial immaturity of the GABAergic system at birth and during the first days of life. At this age, repetitive administrations of progabide cause a protective anticonvulsant action more remarkable than the single injection, particularly when using the higher doses of the substance. In 15-28-day-old rats, the treatment significantly reduces the lethality from status epilepticus but does not substantially modify the incidence of seizures, their latency of appearance, or their evolution toward status epilepticus. As in younger animals, in these rats also pretreatment is more effective than treatment against bicuculline seizures, whatever dose of progabide is used. At this age, therefore, the anticonvulsant properties of progabide appear to be more remarkable than in the previous age, probably because of a higher level of development of the GABAergic system, according to biochemical data on the GABAergic system ontogenesis.

Aging↗
PubMed1985

Bicuculline- and allylglycine-induced epilepsy in developing rats.

The development of bicuculline- and allylglycine-induced epilepsy has been studied in developing rats (6 to 30 days old). The results showed that during the first period of life, in both experimental models, the behavioral modifications were atypical and poorly correlated to corresponding epileptic EEG changes. Successively, a gradual evolution of the electroclinical patterns was observed, with similar characteristics in both bicuculline- and allylglycine-treated animals. Only from the 3rd week did electroclinical patterns similar to those of adult animals and more specific for the type of the convulsant agent appear. These data suggest that during the 1st 2 weeks after birth, the level of global cerebral immaturity, rather than the type of the epileptogenic substance, is the prominent element in the characterization of epileptic manifestations. From the 3rd week, the more advanced level of anatomical, biochemical, and neurophysiologic maturation of the CNS allows a more selective involvement of various cerebral structures with subsequent well defined epileptic features.

Allylglycine↗
PubMed1984

Status epilepticus and brain maturation.

The development of a limbic and a generalized tonic-clonic form of epilepsy, induced by systemic injections of kainic acid and pentylenetetrazol respectively, has been studied in developing rats. The purpose of this research was to investigate the correlations between the maturational stages of the CNS and the electro-clinical manifestations of epilepsy and status epilepticus. In both models of epilepsy, the electro-clinical patterns of seizures typical of the adult animal were reached as early as the third week of life. During the first weeks, atypical behavioural and EEG epileptic manifestations were observed. An attempt has been made to compare the experimental results with the electro-clinical epileptic signs of the infant, in order to suggest some neurophysiological explanations of the peculiar aspects of infantile epilepsy.

Animals↗
PubMed1983

Intracortical and intrahippocampal injections of kainic acid in developing rats: an electrographic study.

Electrographic patterns induced by neocortical and hippocampal microinjections of kainic acid (KA) have been studied in curarized 4-30-day-old rats. In younger (4-6-day-old) animals, both hippocampal and neocortical KA application induced, with a long delay, the appearance of sequences of slow spikes, simultaneously occurring in the cortex and hippocampus. The same pattern was observed in about 60% of animals 7-9 days old. In the remaining 40% of the rats of this age, epileptic abnormalities, initially localized in the neocortical or hippocampal injection site were obtained. The latter pattern always appeared in 10-14-day-old rats. In some of these status epilepticus was also reached. In older (15-30 days) animals, the hippocampal injection caused the appearance of hippocampal seizures, always evolving into status epilepticus. In neocortically injected animals, cortical bursts of polyspikes appeared, with or without hippocampal involvement. After 40-60 min, typical hippocampal seizures occurred, later leading to status epilepticus. The simultaneous hippocampal and neocortical response observed in younger rats is attributed to a massive activation of the immature brain structures. The focal response seems to be correlated with a maturational process of glutamate and/or kainate receptors at both hippocampal and neocortical levels. This process is completed during the third week, when a typical selective activation of the limbic structures is obtained.

Animals↗
PubMed1982

Effects of REMs and PGOs on visual evoked responses during paradoxical sleep of cats.

The amplitude modifications of VERs from paired geniculate stimuli during paradoxical sleep were studied in five cats with chronically implanted electrodes, in the presence of REMs and during PGOs without REMs. In both cases the C5 component of evoked potentials was significantly enhanced with respect to the controls. This facilitation affecting presumably only the postsynaptic component of the response seems linked to signals reaching the visual cortex through other than geniculo-striate pathways. The disinhibition of the second VER appears to be due to intracortical mechanisms, and is not specifically related to phasic events of sleep, such as we previously described during light conditioning and in the absence of eye movements. It is proposed that this effect may be a more general phenomenon caused by changes in cortical activation during eye movement and conditioning.

Action Potentials↗
PubMedDate not supplied

Long-term effects of early status epilepticus on the acquisition of conditioned avoidance behavior in rats.

The acquisition of active avoidance behavior in a shuttle-box apparatus was studied in 45-day-old rats. In these animals a single episode of status epilepticus had been induced by the systemic administration of kainic acid (KA) or pentylenetetrazole (PTZ), when they were 10 or 25 days old. The results were compared with those obtained from animals in which, at the same ages, only saline solution had been injected. In KA-treated rats a decrement of right responses and a prolonged reaction time were observed, with these results more evident in animals treated earlier (10 days). Parallel with the behavioral alterations, the histological, morphometric and morphological examinations revealed neuronal and glial abnormalities at the neocortical level, while no lesions were found in the hippocampus. PTZ-treated rats showed no behavioral alteration nor histological abnormality. The different findings obtained after KA and PTZ injection suggest that not only status epilepticus per se, but the mechanism of action and the neurotoxicity of the convulsant agent, are very important in impairing late performances.

Animals↗