The muscles and motor and sensory nerves of the pregenital abdominal segments were described and discussed in relation to the nerves and muscles of the thorax, as described by other workers. Each of the integumental muscles was named and described with regard to its location, function and innervation. Differences among segments of the same sex and between sexes were noted.A description of a longitudinal muscle, named here the hyperneural muscle, was included. The muscle overlies the abdominal portion of the nerve cord and may be derived from the ventral diaphragm. The most notable features of its structure are chiasmata of fibers which occur at points along its length and which show consistent relationships to the nerve cord and median nerve.A previously undescribed organ, located ventrally at the intersegmental fold, having dual innervation and showing stretch receptor function was described.
SUMMARYThe effects of cholinergic drugs on transmission a t the cercal nervegiant fiber synapse in the desheathed sixth abdominal ganglion of the American cockroach, Periplaneta americana (L.) were evaluated.When due consideration was given to slow diffusion rates of drugs into the ganglion, and t o the enzymic hydrolysis of exogenously applied choline esters by endogenous cholinesterase, the synapse was found to respond in ways consistent with cholinergic transmission. Botulinus toxin, magnesium, and hemicholinium-3, all working presynaptically blocked transmission. Atropine, D-tubocurarine, and hexamethonium produced non-depolarizing blockade at concentrations of 10 -7 M or 10 -6 M . Atropine and d-tubocurarine also blocked the action of exogenously applied acetylcholine. Postsynaptic responses were obtained from acetylcholine (10 -7 M ) , acetyl 0-methyl choline (10 -* M ) , and nicotine
110-8 M ) .The results were discussed with respect to criteria which have been proposed for the indentification of transmitters. It was concluded that considering all of the information available on the cercal nerve-giant fiber synapse, the transmitter is almost certainly Ach.
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