Abstract
1. The aminopyridines (AP) increase the activity recorded on the dorsal roots of an isolated hamster spinal cord preparation. 2. The threshold for 4-AP was 4 X 10(-6) M and the maximum effect was 3 X 10(-5) M. The threshold for 2AP and 3AP was 3 X 10(-5) M and the maximum effect was at 10(-3) M. 3. It took longer for the preparation to recover on washing from treatment with 4-AP than from 2-AP or 3-AP. Washing often showed a transient increase in activity. 4. Treatment with AP changed the pattern of firing so that the activity after treatment and prolonged washing showed a bursting pattern. 5. The activity recorded in the dorsal roots is generated within the spinal cord and may be related to activity of central pattern generators.