Mechanosensory input modulates activity of an autoactive, bursting neuron in Limax maximus

Feeding and salivary neurons located in the buccal ganglia of Limax were monitored extracellularly via their axons in buccal roots while the salivary duct was stretched. Microliter injections of saline were delivered into the salivary duct via a cannula placed in the lumen of the duct. These injections stretched the duct less than spontaneous duct expansions measured in vivo. The bilateral salivary bursters (SBs) are autoactive, bursting buccal neurons that innervate the musculature of the salivary ducts. Feedback from salivary duct stretch modulates SB activity. The modulation of SB activity by stretch feedback gives the duct musculature reflex control over duct contracture. This phenomenon may represent a mechanism to coordinate the processes of salivary secretion and transport. Because the SB is an endogenous burster, its membrane potential and the ionic currents underlying that potential are continually cycling. The SB, therefore, has a changing sensitivity to a constant input throughout its burst cycle. This relationship is clearly shown by the phase-response curve Feeding motor program (FMP) is elicited following the release of a maintained stretch of the duct. These data suggest that an excitatory rebound from inhibition of feeding neurons caused by duct stretch can contribute to the activation of the FMP.