The effect of repeated stimulation on the escape reflex and the acetylcholinesterase activity in different parts of the central nervous system in the crayfish ( Pacifastacus leniusculus and Astacus astacus)

Abstract

1. 1. Repeated mechanical stimulation caused a habituation of the escape reflex of the crayfish Pacifastacus leniusculus but did not change the activity of the AChE in the abdominal ganglia and supraoesophageal ganglion. 2. 2. Repeated electrical stimulation caused a waning of the escape reflex of the crayfish P. leniusculus and Astacus astacus and decreased the activity of AChE in the abdominal ganglia and supraoesophageal ganglion. 3. 3. The decreased AChE activity was not reversed by the addition of the substrate. Substrate concentration for V max (5 × 10 −3 M) and K m (1.6 × 10 −4 M) of the enzyme were the same in the test and control animals. It is suggested that the change in the activity of the AChE was due to a change in the number of active sites of the enzyme. 4. 4. The possible mechanism of the decrease of the activity of the AChE and the significance of the results in the habituation or waning of the escape reflex are discussed.