Abbreviations: AM, antennal muscle; AMNv, antennal motor nerve; AbS, abductor of the scape; AdS, adductor of the scape; LS, levator of the scape; LP, levator of the pedicel; DP, depressor of the pedicel; CI, correlation index; CPG, central pattern generator; IC, injected drug concentration; FC, final drug concentration 2
AbstractThe antennal motor system was activated by the muscarinic agonist pilocarpine in the American cockroach Periplaneta americana, and its output patterns were examined both in restrained intact animals and in isolated CNS preparations. The 3-D antennal movements induced by the hemocoelic drug injection were analyzed in in vivo preparations. Pilocarpine effectively induced prolonged rhythmic movements of both antennae. The antennae tended to describe a spatially patterned trajectory, forming loops or the symbol of infinity (∞). Such spatial regularity is comparable to that during spontaneous tethered-walking. Rhythmic bursting activities of the antennal motor nerves in in vitro preparations were also elicited by bath application of pilocarpine.Cross-correlation analyses of the bursting spike activities revealed significant couplings among certain motor units, implying the spatial regularity of the antennal trajectory. The pilocarpine-induced rhythmic activity of antennal motor nerves was effectively suppressed by the muscarinic antagonist atropine. These results indicate that the activation of the antennal motor system is mediated by muscarinic receptors.