Transient immunosuppression allows transgene expression following readministration of adeno-associated viral vectors |
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Authors: | WC Manning S Zhou MP Bland JA Escobedo V Dwarki |
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Affiliation: | Depto. de Biología Celular, Instituto de Investigaciones Biomédicas, UNAM, México, DF. sitges@servidor.unam.mx |
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Abstract: | The effects of external pH (pHout) variations on the Na+ and on the Ca2+ dependent fractions of the evoked amino acid neurotransmitter release were separately investigated, using GABA as a model transmitter. In 3H]GABA loaded mouse brain synaptosomes, the external acidification (pHout 6.0) markedly decreased the Na+ dependent fraction of 3H]GABA release evoked by veratridine (10 microM) in the absence of external Ca2+, as well as the Ca2+ dependent fraction of 3H]GABA release evoked by high (20 mM) K+ in the absence of external Na+. The depolarization-induced elevation of Na(i)] (monitored in synaptosomes loaded with the Na+ indicator dye, SBFI) and the depolarization-induced elevation of Ca(i)] (monitored in synaptosomes loaded with the Ca2+ indicator dye fura-2) were also markedly decreased at pHout 6. On the contrary, the external alkalinization (pHout 8) facilitated all the above responses. A slight increase of the baseline release of the 3H]GABA was observed when pHout was changed from 7.4 to 8. This effect was only observed in the presence of Ca2+. pHout changes from 7.4 to 6 or to 7 did not modify the baseline release of the transmitter. All the effects of pHout variations on 3H]GABA release were independent on the presence of HCO3-. It is concluded that external H+ regulate amino acid neurotransmitter release by their actions on presynaptic Na+ channels, as well as on presynaptic Ca2+ channels. |
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