Although the mechanism of action of these convulsants fits well with the hypothesized balance of synaptic excitation and inhibition in epilepsy-prone brain regions, it is less well understood how other important convulsants exert their effects. Cholera toxin is an activator of adenylate cyclase and may therefore trigger seizures by mimicking any of the many cellular actions of cAMP and cAMP-dependent protein kinase, including reduction of K+ conductance and facilitation of transmitter release. Tetanus toxin inhibits the release of both excitatory and inhibitory neurotransmit-ters. Epileptiform activity elicited by focal application of alumina hydroxide or cobalt has been used as a model for posttraumatic epilepsy, although the mechanisms underlying seizure generation remain unclear. Pentylenetetrazol is a powerful and widely used convulsant whose mechanism of action is also unknown.
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