ANTAGONISTIC CONTROL OF THE HYPERNEURAL MUSCLE IN PERIPLANETA-AMERICANA (L) (INSECTA, BLATTARIA)

The hyperneural muscle extends longitudinally in the abdomen dorsally to the nerve cord. It is innervated (1) by the six abdominal transvers e nerves branching in pairs from the median nerves, (2) by the 7th tra nsverse nerves arising from the terminal ganglion and (3) by the ramus hyperneuromus-cularis of the nerve VIII A/1 of the terminal ganglion. The results of this study document that the hyperneural muscle is und er antagonistic neuronal control comparable to the sympathetic and par asympathetic innervation of internal organs in vertebrates. Simulation via the transverse nerve 2, transverse nerve 7 or nerve VIII results in a sustained contraction of the hyperneural muscle. In contrast, sti mulation via the transverse nerves 3,4,5 or 6 induces a drastic relaxa tion of the muscle. The only factors knowing initiating a contraction of the muscle are neuropeptides, namely proctolin and corazonin. None of the ''classic'' transmitters tested causes a contraction of the mus cle under isometric conditions. Acetycholine, taurine, histamine and g lycine in concentration of 10(-5) mol/l had no effect on the muscle. T he sequence of decreasing effectiveness was: OA>NA>5-HT>DA=Glu>GABA. O ctopamine is by far the most effective relaxing transmitter at this mu scle. In accordance, the most effective octopamine antagonists, e.g. m aroxepine and mianserin, are also the most effective inhibitors of the relaxation electrically evoked via transverse nerve 5. The pharmacolo gical properties of the octopamine receptors lying on the hyperneural muscle indicate that they resemble the octopamine-1 class of receptors lying on the hyperneural muscle indicate that they resemble the octop amine-1 class of receptors. The cholinergic antagonists scopolamine, a zamethonium and atropine as well as the GABA-antagonists bicuculline, muscinol and baclofen were ineffective. None of the antagonists tested had any inhibiting or potentiating effect on the electrically via tra nsverse nerve 7 evoked contractions of the muscle showing us that in t his activating process biogenic amines or other ''classic'' transmitte rs are not integrated. Summarizing, we can conclude that the inactivat ing mediator at the hyperneural muscle in surely octopamine while the activating mediator most probably proctolin.