CHARACTERIZATION OF A NOVEL CENTRAL PATTERN GENERATOR LOCATED IN THE 7TH ABDOMINAL-GANGLION OF LOCUSTA

The neural activity recorded at the oviducal nerves of semi-intact non-egg-laying locusts and disturbed egg-laying locusts has been examined. A rhythmic motor pattern comprising predominantly three discernible sizes of action potentials could be recorded from disturbed egg-layers but not from non-egg-layers. The larger and smaller action potentials burst in a coordinated way which were mutually exclusive to the medium-sized action potential. The medium-sized action potential was found to produce typical electromyographic responses at the innervated regions of the oviduct while the larger and smaller action potentials produced similar responses at the external ventral protractor of the VIIth abdominal segment. The minimal neural substrate required to produce this rhythmic motor pattern resides entirely in the VIIth abdominal ganglion as shown by transections. The data presented suggests that a central pattern generator controlling the reciprocal contractions of the innervated regions of the oviduct and the external ventral protractors of the VIIth abdominal segment is located in the VIIth abdominal ganglion and is controlled by descending neural inhibition. Possible functions of this central pattern generator are discussed.