Biomedical subjects

M C Iribar

Publications and source records attributed to M C Iribar.

5 recordsLinked to original sources

PubMed1997

Evoked GABA release is not mediated by N-type VDCC in the frontal cortex of awake rats: effects of neomycin.

The purpose of the present study was to analyze the Ca2+ channel involved in GABA release under resting and K(+)-evoked conditions in vivo. We used microdialysis to investigate the effects of the voltage-dependent calcium channel (VDCC) blockers neomycin, kanamycin, and omega-conotoxin GVIA, and the voltage-dependent Na+ channel blocker tetrodotoxin, in the frontal cortex of awake rats. The GABA content in frontal dialysates was analyzed by high performance liquid chromatography coupled to fluorescence detection. Basal GABA release was kanamycin, omega-conotoxin, and tetrodotoxin resistant, whereas neomycin induced a significant increase from the basal level. The K(+)-evoked release of GABA was kanamycin and omega-conotoxin resistant, but tetrodotoxin sensitive. The effects of neomycin were masked by the action of this drug on basal release. These results suggest that neomycin may affect GABA release in the frontal cortex through a mechanism independent of VDCC. In addition, the K(+)-evoked release of GABA in this cortical area was not mediated by the N-type voltage-dependent calcium channels, but was dependent on neural activity or TTX sensitive.

Animals↗

PubMed1997

[Age-related changes in the cytolytic activity of aspartyl aminopeptidase in the cerebral cortex of the rat].

INTRODUCTION: Recently, neurotoxicity mediated by excitatory amino acids has been considered to be the etiopathogenic basis of various neurodegenerative processes, including aging of the brain. OBJECTIVE: Since the enzyme aspartyl-aminopeptidase (Asp-AP) may play a role in modifying the concentration of the cytotoxic amino acids glutamate and aspartate, we studied the changes in its activity in the rat cerebral cortex, which were possibly related to age. MATERIALS AND METHODS: Homogenates of frontal, parietal, temporal and occipital cortex were obtained from young and old rats. The activity of Asp-AP in these homogenates determined by fluorimetry. RESULTS: Our results showed a significant age-dependent drop in Asp-AP activity in the frontal, parietal and occipital cortices, with little change in the temporal cortex. CONCLUSIONS: These results may be understood as part of a general schedule of age-dependent modifications of the cerebral protease systems.

Aminopeptidases↗

PubMed1987

Hemidecortication selectively alters release of glutamate in perfusates collected from cerebral cortex of unrestrained rats.

The effect of hemidecortication on the in vivo release of amino acids was examined in different areas of the cerebral cortex of the freely-moving rat. After one side of the cortex was lesioned by aspiration, four guide tubes for push-pull perfusion were implanted chronically on the contralateral side so as to rest above the frontal, parietal, temporal and occipital areas of the cortex. After 10-14 days elapsed, each of these regions was perfused with an artificial cerebrospinal fluid (CSF) at a rate of 25.0 microliter/min. Two types of assays were undertaken to determine the release of either newly synthesized amino acids from [14C]glucose precursor or the actual endogenous content in samples of perfusate. The separation of the [14C]amino acids was performed by thin layer chromatography, whereas endogenous amino acids were separated by HPLC with electrochemical detection and quantitated in the range of 1.0-10.0 picomoles. When compared to the control group, samples collected in the hemidecorticate rat showed no significant differences in the new synthesis of glutamate, aspartate, glutamine, glycine, and GABA from the precursor. On the other hand, the analysis of the endogenous amino acid neurotransmitters revealed that the levels of glutamic acid and glutamine declined in samples obtained from the parietal and frontal cortex, respectively. These results implicate further the potential role of glutamic acid as a neurotransmitter of interhemispheric connections in the cerebral cortex.

Animals↗

PubMed1984

[Possible mechanism of action of a water-soluble tissue extract on arterial pressure in the rat].

A double hypo-hypertension effect is seen when a hydrosoluble splenic extract at pH 5 is injected to rats intravenously. The hypotensive effect may be caused by local vasodilating agents, such as histamine. The hypertensive one does not appear in adrenoprive animals or in rats treated with inhibitors of prostaglandin synthesis which suggests that the mechanism for this effect is complex.

Adrenalectomy↗

PubMedDate not supplied

Alanyl-aminopeptidase activity decrease in cerebrospinal fluid of Alzheimer patients.

We analyzed the amino acid concentrations and aminopeptidase activities in plasma and the cerebrospinal fluid (CSF) of Alzheimer patients. Correlations were calculated between these parameters and the degree of cognitive impairment, duration of the disease and age. In comparison with a control group, no changes were found in the levels of amino acids in CSF or plasma of Alzheimer patients. Alanyl-aminopeptidase activity was significantly lower in the CSF of Alzheimer patients, whereas no differences in CSF were detected as regards the remaining aminopeptidases. The plasma/CSF ratio for aminopeptidase activities was higher in AD patients than in controls, although the difference was only significant for alanyl-aminopeptidase. Amino acid ratios did not show this general tendency. The correlations between plasma aspartate and glutamate concentrations and the stage of the disease, measured with the Mini Mental State Examination, were studied. Changes in aminopeptidase activities and their role in protein dysfunction underlying Alzheimer disease are discussed.

Aged↗