Abstract
1. The involvement of intracellular calcium and calmodulin in the modulation of plateau potentials in motoneurones was investigated using intracellular recordings from a spinal cord slice preparation. 2. Chelation of intracellular calcium with BAPTA-AM or inactivation of calmodulin with W-7 or trifluoperazine reduced the amplitude of depolarization-induced plateau potentials. Inactivation of calmodulin also inhibited facilitation of plateau potentials by activation of group I metabotropic glutamate receptors or muscarinic receptors. 3. In low-sodium medium and in the presence of tetraethylammonium and tetrodotoxin, calcium action potentials evoked by depolarization were followed by a short hyperpolarization ascribed to the calcium-activated non-selective cationic current (ICAN) and by a dihydropyridine-sensitive afterdepolarization. The amplitude of the afterdepolarization depended on the number of calcium spikes and was mediated by L-type calcium channels. 4. The dihydropyridine-sensitive afterdepolarization induced by calcium spikes was reduced by blockade of calmodulin. 5. It is proposed that plateau potentials in spinal motoneurones are facilitated by activation of a calcium-calmodulin-dependent pathway.
| Original language | English |
|---|---|
| Journal | Journal of Physiology |
| Volume | 528 Pt 1 |
| Pages (from-to) | 107-13 |
| Number of pages | 7 |
| ISSN | 0022-3751 |
| Publication status | Published - 1 Oct 2000 |
Keywords
- Animals
- Calcium
- Calcium Channels, L-Type
- Calmodulin
- Dopamine Antagonists
- Egtazic Acid
- Intracellular Fluid
- Membrane Potentials
- Motor Neurons
- Receptors, Metabotropic Glutamate
- Receptors, Muscarinic
- Sodium
- Spinal Cord
- Tetraethylammonium
- Tetrodotoxin
- Trifluoperazine
- Turtles