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Biomedical subjects

M E Moneta

Publications and source records attributed to M E Moneta.

10 recordsLinked to original sources
PubMed1994

Electrical stimulation of the kindled hippocampus briefly increases extracellular dopamine in the nucleus accumbens.

The effect of electrical stimulation of the dorsal hippocampus on accumbens dopamine release was examined. Stimulation of the kindled hippocampus that produced stage 3 seizures evoked a brief increase in extracellular DA and DOPAC levels in the contralateral nucleus accumbens. In contrast, similar stimulation early in the development of kindling producing a stage 1 seizure did not evoke this increase.

Amygdala↗
PubMed1993

Cell adhesion molecule expression in the regenerating rat facial nucleus.

Transection of the rat facial nerve leads to an intrinsic microglial reaction in the facial nucleus. In the present study, we have examined immunocytochemically the expression of cell adhesion molecules during this process. Resting microglia constitutively expressed the LFA-1 alpha and beta chain (CD11a and CD18) in the white matter, rather than in the intact, control facial nucleus. From 24 h after facial nerve transection onward, activated microglia showed an increased expression of LFA-1 alpha and beta. The immunoreactivity reached its peak around day 7 following axotomy, i.e. at a time when activated microglia are found in a close perineuronal position. In contrast, the expression of the principal ligand of LFA-1, i.e. ICAM-1, remained unchanged following axotomy; the immunoreactivity being constitutively found on cerebral blood vessels. Increased LFA-1 expression thus appears to be a general marker for microglial activation and might further be involved in the rearrangement of the microglial cytoskeleton upon activation of this cell.

Animals↗
PubMed1990

Perforant path kindling induces differential alterations in the mRNA levels coding for prodynorphin and proenkephalin in the rat hippocampus.

The effect of perforant path kindling on the levels of mRNAs coding for proenkephalin and prodynorphin in hippocampus and frontal cortex of rats was measured using RNA blot analysis. In rats showing stage 3 kindled seizures, after consecutive stimulation of the right perforant path, a decrease in the level of prodynorphin mRNA and an increase in levels of proenkephalin mRNA in the ipsilateral hippocampus was found. In addition, the levels of prodynorphin were also decreased in the contralateral hippocampus. No changes in the opioid peptide mRNAs were found in the frontal cortex of the animals. The altered mRNA levels in the hippocampus returned to normal 8 days following cessation of the electrical stimulation. However, at that time a single stimulus was still effective in producing stage 3 kindling seizures. These findings indicate that (1) the opioid peptide gene expression in the hippocampus can be transynaptically altered by kindling of the perforant path and (2) that the opioid peptides may play a role in the development, but not in the maintenance of kindling.

Animals↗
PubMed1989

Inositol 1-phosphate formation in long-term potentiation and kindling.

Long-term potentiation (LTP) in the CA3 hippocampal subfield, elicited in vivo, produced significant increases in basal and in carbachol- and noradrenaline-induced hydrolysis of phosphatidylinositol-4,5-biphosphate (PtdIns(4,5)P2) as measured by the accumulation of InsP1 in hippocampal slices in vitro. Kindling, however, resulted in significant decreases in basal and in carbachol- and noradrenaline-induced accumulation of InsP1 in hippocampal slices. N-Methyl-D-aspartate (NMDA) receptors do not directly alter the hydrolysis of PtdIns(4,5)P2 in either LTP or kindling. These results demonstrate that LTP and kindling are associated with opposite alterations in efficacy of the main receptors mediating the hydrolysis of PtdIns(4,5)P2.

Animals↗
PubMed1988

Changes in spontaneous activity of medialis dorsalis thalamic neurones during sleep and wakefulness.

In chronic unanaesthetized cats unitary activity of medialis dorsalis (MD) thalamic neurones was recorded during wakefulness (W), slow wave (SWS) and desynchronized (DS) sleep. The discharge pattern of these neurones changes during SWS compared to W. Comparison between desynchronization of W and DS shows a change in the mean frequency, being higher in W than in DS. The results suggest that MD neurones participate in the organization of the sleep-wakefulness cycle.

Action Potentials↗
PubMed1987

Levels of prodynorphin mRNA in rat dentate gyrus are decreased during hippocampal kindling.

The effect of hippocampal kindling on the levels of prodynorphin mRNA in rat hippocampus was examined by in situ hybridization using a synthetic oligonucleotide probe. Cryostat tissue sections were hybridised with a 32P-labelled 100 mer DNA probe complementary to the coding region of rat prodynorphin mRNA, and exposed to X-ray film. In rats exhibiting stage 4 seizures, the levels of prodynorphin mRNA in the dentate gyrus were dramatically reduced compared to control animals. This suggests that the development of kindling is accompanied by a reduction in the rate of synthesis of peptides derived from prodynorphin.

Animals↗
PubMed1986

Sodium pathway markers in normal and kindled frog brains.

The present report evaluates Na,K-ATPase activity as well as Na channel levels in the frog telencephalon after kindling, i.e. the acquisition of an epileptic focus through localized low-voltage electrical stimulation of one hemisphere. K-dependent phosphatase activity and binding of tritiated ouabain were measured, revealing no change in Na,K-ATPase activity 14 h after the last seizure. Na channels were measured by binding assays using a tritiated ethylenediamine tetrodotoxin derivative. Na channels were reduced in kindled brain as compared to controls.

4-Nitrophenylphosphatase↗
PubMed1986

Critical period plasticity of kitten visual cortex is not associated with enhanced susceptibility to electrical kindling.

The goal of this study was to determine whether the use-dependent malleability of visual cortex functions which is particularly pronounced in 4-week-old kittens correlates with enhanced susceptibility to kindling. For that purpose the effects of high-frequency electrical stimulation were compared in the visual cortex of 4-week-old kittens and of adult cats. The striate cortex of one hemisphere was stimulated with a single train of pulses whose intensity was set just above the threshold for the elicitation of afterdischarges (ADs). In kittens the AD thresholds were consistently higher than in adults and with repeated stimulation, the ADs tended to disorganize, to decrease in amplitude and duration and to become more restricted to the site of stimulation after about 6 stimulations. In the adult, by contrast, the ADs remained well organized and constant in duration throughout 30 stimulations. They showed an increase in amplitude and spike frequency and spread with increasing consistency to the other hemisphere. No electrographic or behavioural signs of epileptic activity developed in kittens, while in adults ADs were on occasion followed by irregular spike activity associated with behavioural states resembling absences. We conclude that the visual cortex possesses powerful mechanisms to prevent the development of supracritical excitatory states, these mechanisms being more effective in the kitten than in the adult.

Age Factors↗
PubMed1983

A temperature threshold for frog hippocampal kindling.

The present report documents the influence of temperature (T) on kindling, i.e. the acquisition of an epileptic focus through localized low voltage electrical stimulation, In the frog hippocampal cortex. Kindling cannot be induced if T is lowered from 18.0 degrees C to just 17.0 degrees C. The possible mechanisms underlying this T threshold are briefly discussed.

Animals↗