Abstract
The effects of the cannabinoid receptor agonist Win55,212 on Ca2+ channels were studied in rat hippocampal neurons grown in primary culture. Win55,212-2 inhibited whole-cell Ba2+ currents through Ca2+ channels by both CB1 receptor-mediated and direct mechanisms. The concentration dependent inhibition of the current showed two clear phases, a high-affinity receptor- mediated phase (IC50 = 14 ± 2 nM) that was stereoselective and sensitive to a CB1 receptor antagonist, 300 nM SR141716, and a non-saturating phase that was neither stereoselective nor inhibited by SR141716. These concentration-dependent effects were paralleled by Win55212-induced inhibition of glutamatergic synaptic transmission. Win55,212-2 (100 nM) inhibited both ω-agatoxin IVA- and ω-conotoxin GVIA-sensitive currents. Thus, activation of cannabinoid receptors inhibits N- and P/Q-type Ca2+ channels. Activation of cannabinoid receptors inhibited only a fraction of the whole-cell Ca2+ channel current (17 ± 2%) even though more than half of the whole-cell Ba2+ current was carried by N- and P/Q-type Ca2+ channels. Concentrations of agonist greater than 1 μM inhibited Ca2+ channels directly.
Original language | English (US) |
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Pages (from-to) | 77-84 |
Number of pages | 8 |
Journal | Brain Research |
Volume | 783 |
Issue number | 1 |
DOIs | |
State | Published - Feb 2 1998 |
Keywords
- Calcium channel
- Cannabinoid
- Hippocampus
- Patch-clamp