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Picrotoxin convulsions involve synaptic and nonsynaptic mechanisms on cultured mouse spinal neurons
Abstract:
The cellular mechanisms underlying picrotoxin-induced convulsive activity were studied by using mouse spinal neurons growing in tissue culture. Picrotoxin-induced convulsive activity in most but not all of the cells studied. The activity could be inverted by polarizing to positive potentials and eliminated either by decreasing the ratio of calcium to magnesium or by applying tetrodotoxin. When applied locally to individual cells, picrotoxin lowered spike threshold and induced spontaneous firing in some but not all cells tested. The results suggest that picrotoxin-induced convulsive activity involves rapidly summating synaptic activity which may be evoked by high-frequency repetitive firing.
Insights
Picrotoxin causes convulsive activity in mouse spinal neurons by affecting synaptic activity. This neuronal hyperexcitability can be reversed by altering electrical potentials or ion concentrations.
Area of Science:
- Neuroscience
- Cellular Biology
- Pharmacology
Background:
- Picrotoxin is known to induce convulsive activity.
- The precise cellular mechanisms remain incompletely understood.
Purpose of the Study:
- To investigate the cellular mechanisms of picrotoxin-induced convulsive activity in mouse spinal neurons.
- To identify factors influencing picrotoxin's effects on neuronal excitability.
Main Methods:
- Primary mouse spinal neurons cultured in vitro.
- Electrophysiological recordings to assess neuronal activity.
- Pharmacological manipulation with picrotoxin, tetrodotoxin, and varying calcium/magnesium ratios.
Main Results:
- Picrotoxin induced convulsive activity in a majority of neurons.
- This activity was reversible by polarizing potentials and by altering calcium/magnesium ratios.
- Tetrodotoxin abolished picrotoxin-induced activity.
- Local picrotoxin application lowered spike threshold and induced spontaneous firing in some neurons.
Conclusions:
- Picrotoxin-induced seizures involve synaptic mechanisms.
- High-frequency neuronal firing may trigger picrotoxin's effects.
- Neuronal excitability is modulated by synaptic activity and ion balance.