Muscarinic presynaptic inhibition of neostriatal glutamatergic afferents is mediated by Q-type Ca2+ channels
Por:
Barral J., Galarraga E., Bargas J.
Publicada:
1 ene 1999
Resumen:
Cholinergic presynaptic inhibition was investigated on neostriatal glutamatergic transmission. Paired pulse facilitation (PPF) of orthodromic population spikes (PS) were used to construct a concentration-response relationship for muscarine on presynaptic inhibition. Muscarine had an effect proportional to its extracellular concentration with an EC50 (mean ± standard estimation error) of: 2.5 ± 1.5 nM, and a maximal effect (saturation) of 245 ± 16%. Several peptidic toxins against some voltage- gated Ca2+-channels increased PPF indicating that the Ca2+-channels they block participate in transmitter release. However, neither 1 ?M ?-conotoxin GVIA, a specific blocker of N-type Ca2+-channels, nor 10-30 nM ?- agatoxinTK, a selective blocker of P-type Ca2+-channels, were able to occlude muscarine's effect on presynaptic inhibition. Nevertheless, 100-400 nM ?-agatoxinTK occluded muscarine's action on PPF in a dose-dependent manner. These results are consistent with Q-type Ca2+-channels mediating muscarinic presynaptic inhibition of neostriatal afferents.
Filiaciones:
Barral J.:
Neurociencias, ENEP Iztacala, UNAM, México City, Mexico
Galarraga E.:
Inst. de Fisiologiá Celular, UNAM, Mexico City, Mexico
Bargas J.:
Inst. de Fisiologiá Celular, UNAM, Mexico City, Mexico
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