Neurogenic contractile activity of the penis retractor muscle of Helix pomatia L.

Using convential mechanical and electromyographic recording methods 2 distinct types of neurogenically elicited activity can be observed in the penis retractor muslce (PRM) of Helix pomatia: (1) rhythmic, phasic contractions correlated with single or a few compound action potentials and (2) intervening, strong, prolonged contractions accompanied by sustained, high frequency electrical muscle activity. The 2 distinct types of muscle activity which seem to play a part in the normal behaviour of the PRM in the intact animal are mediated by both the central nervous system and peripheral neurons. While central neuronal structures are involved in causing the strong, prolonged contractions, the phasic activity is initiated by peripheral neuronal structures located at the proximal end of the PRM. There is evidence that the transmission of the excitation at the neuromuscular level of central and peripheral origin is mediated by ACh.