Aminopyridine-sensitivity of spinal cord white matter studied in vitro

Sections of dorsal columns of the spinal cord were removed from rats of various ages and studied in a sucrose gap chamber. The potassium channel blocking agent, 4-aminopyridine (4-AP), led to a pronounced increase in the area of the compound action potential of immature dorsal column axons. During the course of maturation this effect was attenuated but not lost. Occlusion experiments indicate that the 4-AP-elicited increase in area of the response was likely the result of multiple action potential discharge, an effect also present in dorsal root but not ventral root fibers (Bowe et al. 1985). These results indicate that the 4-AP-elicited changes in action potential characteristics previously described for sensory fibers in the peripheral nervous system are also present in the central nervous system extensions of these axons.