MATHEMATICAL-MODELING OF THE ENTERIC NERVOUS NETWORK .2. FACILITATIONAND INHIBITION OF THE CHOLINERGIC TRANSMISSION

The pharmacokinetic responses of the cholinergic enteric neurone to tr eatment with acetylcholinesterases, tetrodotoxin, some chloride salts of divalent cations, botulinum toxin, beta-bungarotoxin and changes in the concentration of calcium ions in the external medium and repetiti ve stimulation are presented. The numerical results obtained reproduce quantitatively the effects of toxins and salts of divalent cations ac ting at different levels of acetylcholine release from the nerve-termi nal. The addition of cholinergic agonists potentiates the action of ac etylcholine and increases the amplitude of the generated excitatory po stsynaptic potential. A decrease in the concentration of extracellular Ca2+ ions reduces the amplitude of the excitatory postsynaptic potent ial and significantly increases synaptic transmission time. The effect of tetrodotoxin is the blockade propagation of the action potential a long the nerve axon and, as a consequence, acetylcholine release from the vesicular store. All these effects have been shown to be dose-depe ndent. The repetitive stimulation of the neurone reproduces the effect s of accumulation and potentiation. The possible applications of the m odel for the analysis of the enteric nervous system function are discu ssed.