Electrical activity of neurohaemal tissue in the stick insect, Carausius morosus

Preparations of the isolated transverse nerve of the median (unpaired) nervous system of the stick insect show spontaneous electrical activity in the form of action potentials. There are no cell bodies of neurones in these preparations so the action potentials must arise in isolated processes of the cells. These may be axons belonging to neurosecretory cells in the central nervous system or processes of peripheral neurosecretory cells. Most of the action potentials resemble those described for other neurosecretory cells in having a spike duration that is longer than that of an ordinary neurone, in this case the sensory neurone of the dorsal stretch receptor. A few have a similar form and duration to the sensory spike. It is postulated that these action potentials are generated either by the passage of neurosecretion through the cell membrane or by excitation of processes by the newly released material. If they have adaptive significance it may be to monitor the release of secretion.