Elektrophysiologische Untersuchungen am Frontalganglion von Periplaneta americana L.

Abstract

The frontal ganglion is an important part of the stomodeal division of the visceral nervous system. It is involved in the control of intake of food and water and of crop emptying as well as in the control of production and/or release of neurosecretory materials. Consequently it also has an influence upon the waterbalance, oocyte development, vitellogenesis etc. Investigations on the electrophysiological activities in the stomatogastric nervous system have not been published until now. This study deals with the spontaneous activities of the frontal ganglion of the cockroach, Periplaneta americana. Extracellular recordings were made with suction electrodes. From both frontal connectives as well as from the recurrent nerve one can detect clear irregular activities coming from the isolated ganglion. Newly moulted animals show in 70% of the cases volley like discharges, which are identical with the rhythm in the nervus connectivus (see below) and are lost in a higher ground activity at the latest four hours after ecdysis. The nervus connectivus consists of only two axons and its cell bodies are located in the protocerebrum. Each axon splits into three branches inside the neuropile of the frontal ganglion. One branch goes to the recurrent nerve, the others to the frontal connectives. From this nerve one can detect extreme regular volley-like discharges from the ganglion ( in vitro and in vivo) to the cell bodies in the protocerebrum (antidromic transmission!). Each cycle lasts 1–4 sec separated by a silent period of few seconds. The volleys consist in our records with suction electrodes of two types of spikes differing in height. Each type supplies half of the total spike number and may relate with the two axons of the nerve. At the end of each volley both the spike types show an increase in frequency and at the same time a decrease in amplitude. From the nerves N1, N2, N3 and N5, only in the cases of N3 and N5 is there spontaneous activity coming from the ganglion. The nerve N3 is more active than N5. From the tritocerebrum heavy spontaneous activity occurs between the frontal connectives and the frontal ganglion. This is similar to the activity detected in the opposite direction. It is essential that the brain-suboesophageal ganglion complex remains undamaged. If the two connectives between subesophageal ganglion and the first thoracic ganglion are dissected carefully and successively the activity may remain. These experiments are performed in situ. The recurrent nerve as well as the other nerves (N. connectivus, N1, N2, N3 and N5) never show spontaneous activity in the direction of the frontal ganglion.