Pharmacological characterisation of voltage-sensitive calcium channels and neurotransmitter release from mouse cerebellar granule cells in culture
✍ Scribed by Thomas Varming; Palle Christophersen; Arne Schousboe; Jørgen Drejer
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 145 KB
- Volume
- 48
- Category
- Article
- ISSN
- 0360-4012
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✦ Synopsis
Using subtype-specific Ca-channel blockers, we have characterised the voltage-sensitive Ca 21 currents as well as neurotransmitter release from cultured mouse cerebellar granule cells. The whole cell version of the patch clamp technique was adapted to monitor the isolated Ca-channel currents. The currents were activated at potentials more positive than 240 mV and were composed of at least four pharmacological distinct components being sensitive to nifedipine (35%), v-conotoxin GVIA (10%), and v-agatoxin IVA (42%) corresponding to L-, N-, and P-channel-mediated currents. The insensitive fraction (13%) possibly represented R channels. High potassium-evoked release of 3 H-D-aspartate was used as a model of synaptic release. These studies were performed at relatively mild stimulation conditions (30 mM K 1 , 0.4 mM Ca 21 ), and 85% of the evoked release was Ca 21 dependent as well as tetrodotoxin and Cd 21 sensitive. Nifedipine and v-agatoxin IVA dose dependently (IC 50 values of 10 nM and 0.7 nM, respectively) blocked most of the release, whereas v-conotoxin MVIIA (IC 50 5 5 nM) caused partial blockage. The results indicate that several subtypes of voltage-sensitive Ca channels are present in mouse cerebellar granule cells. Furthermore, the data suggest that L, N, and P channels act in concert in the neurotransmitter release process.