Biomedical subjects

M T Ciotti

Publications and source records attributed to M T Ciotti.

57 records · Page 4Linked to original sources

PubMed1983

Enrichment of differentiated, stellate astrocytes in cerebellar interneuron cultures as studied by GFAP immunofluorescence and autoradiographic uptake patterns with [3H]D-aspartate and [3H]GABA.

A study was undertaken to correlate the morphology expressed by astroglial cells in post-natal cerebellar, interneuron-enriched primary cultures, and the ability of these cells to accumulate putative neurotransmitter amino acids. Astroglial cell morphology, as studied by GFAP immunofluorescence staining showed considerable changes during the culture period considered (up to 12 days in vitro). While the total number of GFAP-positive cells decreased with time (cell multiplication was prevented by cytosine arabinoside), a progressive enrichment of stellate astrocytes (cells bearing multiple radially arranged processes) and a striking increase in size of these cells was noted. In 12 DIV cultures stellate astrocytes accounted for 70-80% of the astrocytes present, and could reach a diameter of over 300 micron. The L-glutamate analogue, [3H]D-aspartate, was avidly taken up by all the astrocytes, independently of their shape and stage of differentiation. Astroglial cell morphology as delineated by [3H]D-aspartate autoradiography was identical to that evidenced by GFAP staining. On the other hand, [3H]GABA was accumulated in substantial amounts only by the stellate astrocytes, that is by the cells showing greater morphological differentiation. Astrocytes of other shapes were only lightly labelled by [3H]GABA in 2 DIV and 5 DIV cultures, and even less at later stages. Even within the stellate astrocyte population, the extent of [3H]GABA labelling was very variable, from one cell to another. Autoradiographic examinations and the determination of the IC50s for GABA uptake inhibitors consistently indicated that the GABA transport system present in stellate astrocytes did not have the features generally attributed to a glial transport system. In fact, beta-alanine was a very weak inhibitor, while nipecotic acid and ACHC were strongly inhibitory; DABA inhibitory potency fell somewhere in between. [3H]GABA uptake into the inhibitory interneurons present in the cultures showed similar sensitivity to GABA transport inhibitors.

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PubMed1982

Selective release of glutamate from cerebellar granule cells differentiating in culture.

The aim of the present study was to assess whether endogenous and newly synthesized glutamate can be released from differentiating cultured cerebellar granule cells in a way compatible with a neurotransmitter role. Granule cells from 8-day-old rat cerebella were grown in basal Eagle's medium with 10% fetal calf serum for 2-12 days in vitro (DIV), then washed with Krebs-Ringer medium, and labeled for 45 min with tracer amounts of radioactive glutamine. Subsequently, the release of endogenous glutamate and of newly formed radioactive glutamate was measured in basal conditions and upon depolarization with elevated K(+) concentration or veratridine. At 2 DIV, the release of endogenous and newly synthesized glutamate evoked by high K(+) concentration was small and Ca(2+) independent, but it progressively and steadily increased (up to 8- to 10-fold) and became Ca(2+) dependent (up to 80-85%) at later stages (4, 8, and 12 DIV). Veratridine was almost ineffective with cells at 2 DIV but greatly increased glutamate release (endogenous and neosynthesized) at 8 DIV, and its action was totally antagonized by tetrodotoxin. The level and synthesis of glutamate remained fairly constant in cells from 2 to 12 DIV. gamma-Aminobutyric acid synthesis from radioactive glutamine was about 3% of that of glutamate, and gamma-aminobutyric acid release (endogenous and neosynthesized) was not measurable. Aspartate synthesis was about 10% of that of glutamate, and the high K(+) concentration-evoked release of this amino acid was modest and scarcely affected by Ca(2+). Neither high K(+) concentration nor veratridine was able to induce glutamate release from confluent cerebellar astrocyte cultures at 14 DIV, although the level and synthesis of the amino acid were comparable to those in granule cells. In conclusion, the data show that a stimulus-coupled release of endogenous and neosynthesized glutamate is progressively expressed by cerebellar granule cells differentiating in culture, and this strongly supports the concept that glutamate is the neurotransmitter of these cells.

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PubMedDate not supplied

Tachykinin neuropeptides in cerebellar granule neurons: an immunocytochemical study.

We previously demonstrated that exogenously administered neurokinin A and neurokinin B, but not substance P, increased the sensitivity of cultured cerebellar granule neurons (CGNs) to glutamate. In the present study, the presence of tachykinin neuropeptides in CGNs was tested by confocal-based immunofluorescence. We found that neurokinin A and neurokinin B are present in CGNs but absent in astrocytes while substance P is abundant in astrocytes but absent in CGNs. It is postulated that the different localization of tachykinin neuropeptides in CGNs and astroglial cells has a physiological role in the modulation of excitatory transmission.

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