Neuromuscular transmission in the gastrocnemius muscle of young domestic and wild pigs.

The gastrocnemius muscle was stimulated in situ in young female domestic pigs (DP, Sus scrofa domestica, German Landrace; n = 24) and in European wild pigs (WP, Sus scrofa scrofa; n = 20), by short (0.1 ms) square-wave impulses via the sciatic nerve. Evoked compound action potentials were recorded from the sciatic nerve, from the Ramus muscularis distalis of the tibial nerve and from the end plate region of the muscle tissue. Maximum nerve conduction velocities (NCV) were 58.8 +/- 10.4 m/s in DP and 77.7 +/- 16.5 m/s in WP. Time of neuro-muscular transmission ("distal latency") for evoked compound action potentials from the Ramus gastrocnemius of the tibial nerve into the gastrocnemius muscle was 2.32 +/- 0.54 ms in DP and only 1.27 +/- 0.25 ms in WP. Electromechanical coupling time intervals in the gastrocnemius muscle were 11.95 +/- 2.26 ms in DP and 9.95 +/- 1.07 ms in WP. Motor end plates were visualized histochemically and classified as of the red, intermediate and white type according to their shape and arborization. High extrajunctional acetylcholinesterase activity was observed in the close vicinity of the junctions of muscles in young DP (3.5 month, 40 kg), which was absent in WP muscles and also in DP muscle at older age.