Fig. 6.

Long-term hyperexcitability induced by transecting neurites of isolated sensory and motor neurons in the presence or absence of hemolymph in the culture medium. A, Examples of repetitive firing during testing of a control sensory neuron and a sensory neuron, the outgrowing neurites of which had been transected 1 d earlier. The test stimulus was a 1 sec depolarizing pulse injected into the neuronal soma through the recording electrode. Injected current was set at 2.5 times that required to reach spike threshold during a previous series of 20 msec pulses. B, Repetitive firing in sensory neurons 1 d after neurite transection. The mean ± SEM number of spikes evoked by the test stimulus was enhanced by previous transection but unaffected by the presence or absence of hemolymph during the test. Hemolymph present,n = 12 control and 10 transected cells,p < 0.005; hemolymph absent, n= 14 control and 6 transected neurons, p < 0.005.C, Repetitive firing in motor neurons 1 d after neurite transection. Firing was enhanced by previous transection and unaffected by hemolymph during the test. Hemolymph present,n = 6 control and 3 transected cells,p < 0.05; hemolymph absent, n= 8 control and 8 transected neurons, p < 0.05.