Flight activity mediated by intracellular stimulation of dorsal giant interneurons of the cockroachPeriplaneta americana

Abstract

1. Flight activity can be initiated in legless cockroaches by stimulating a single dorsal giant interneuron (dGI) intracellularly with a train of current pulses. Ventral giant interneurons (vGIs) do not initiate flight activity. 2. The initial directional responses in leg motor neurons which are characteristic of running are still evoked prior to flight initiation. 3. For short flights the number of bursts in wing muscles (flight bursts) increases as the number of action potentials in the dGI is increased. 4. Paired stimulation of dGIs evokes longer flight sequences. Moreover, a subthreshold train of action potentials in a single dGI can evoke flight if the train arrives within 500 ms of a previous flight. 5. In flight motor neurons (FMNs), an initial depolarization precedes rhythmic oscillations that are associated with flight bursts. The timing of dGI activity is appropriate for eliciting the initial depolarization as well as the rhythmic oscillations. Stimulation of single dGIs with trains of current pulses evokes both phases of the FMN response, probably via polysynaptic pathways. 6. Activity in the intracellularly stimulated dGI need not reach the mesothoracic ganglion directly in order to evoke coordinated flight activity in both the meso- and metathoracic ganglia.