Different effects of 4-aminopyridine on regenerated cutaneous and muscular rat sciatic nerve branches.
Developing and regenerated myelinated rat dorsal and ventral root fibers respond differently to the fast potassium channel blocking agent 4-aminopyridine (4-AP). To pursue this issue further, we made unilateral sciatic nerve crushes in adult rats. Sural (SN) and lateral gastrocnemius (LGN) nerve branches were collected 4-6 months later, for physiological and morphological examination. Regenerated and control nerves in Ringers solution showed generally similar compound action potential (CAP) waveforms, but CAPs of regenerated SNs and LGNs in 4-AP were markedly different. While regenerated SNs showed a prominent late CAP negativity with a "rippled" appearance and markedly compromised recovery properties, the CAP and recovery properties of regenerated LGNs were minimally changed. Light and electron microscopic examination of SN and LGN fibers failed to reveal any features obviously related to the observed physiological differences. We conclude, that the effect of 4-AP on regenerated cutaneous afferents differs from its action on regenerated muscular afferents and efferents. This physiological diversity lacks obvious structural correlates.
Bowe
C M
CM
Department of Neurology, University of California at Davis, Sacramento.
Hildebrand
C
C
D015761:4-Aminopyridine / Q000494:pharmacology*; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004594:Electrophysiology; D005260:Female; D008854:Microscopy, Electron; D009132:Muscles / Q000187:drug effects / Q000294:innervation*; D009409:Nerve Crush; D009413:Nerve Fibers, Myelinated / Q000187:drug effects / Q000648:ultrastructure; D009416:Nerve Regeneration / Q000187:drug effects*; D011901:Ranvier's Nodes / Q000187:drug effects / Q000648:ultrastructure; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000187:drug effects* / Q000648:ultrastructure; D012867:Skin / Q000187:drug effects / Q000294:innervation*; D013497:Sural Nerve / Q000187:drug effects / Q000648:ultrastructure
D015761:4-Aminopyridine