Evidence of a neural loop involved in controlling spermathecal contractions in Locusta migratoria

The control of spermathecal contractions in Locusta migratoria via a neural loop was demonstrated using mechanical stimulation and electrophysiologica l recordings. Extracellular electrophysiological recordings from the recept aculum seminis nerve (N2B2), which innervates the spermathecal sac, were co nducted during mechanical stimulation of the genital chamber sensory cells. Activation of the genital chamber sensory cells, using a glass probe appro ximating the shape and size of an egg, was found to increase the action pot ential frequency and initiate bursts of action potentials if a tonic freque ncy of action potentials was present prior to stimulation. If the motor pat tern initially consisted of bursts of action potentials, then mechanical st imulation of the genital chamber sensory cells resulted in an increase in f iring frequency, in most preparations, with the bursting remaining. Removal of the probe from the genital chamber always returned the motor activity t o that noted prior to sensory cell stimulation. Simultaneous electrophysiol ogical recordings from both the left and right receptaculum seminis nerves (N2B2) revealed that the bursts of action potentials were coordinated, alth ough individual action potentials were not coupled one to one. Activation o f the genital chamber sensory cells also resulted in increases in spermathe cal contraction frequency, an effect which was coordinated with the changes in motor activity. It is proposed that an egg in the genital chamber activ ates the sensory cells resulting in increases in spermathecal contraction f requency and the subsequent release of spermatozoa onto the micropyle of th e egg for fertilization. (C) 2001 Elsevier Science Ltd. All rights reserved .