We have examined the musculature and motor patterns of the foregut and the role of the frontal ganglion in the adult moth Manduca sexta. During adult development, the structure of the foregut changes from a simple straight tube to a pump consisting of a flexible-roofed chamber or cibarium, with dilator muscles that raise the roof to draw in fluids and a compressor to push it down and force the fluid down the thin-walled esophagus. The frontal ganglion drives the activity of this cibarial pump during feeding, which is triggered by the application of sucrose solution or water to the proboscis. The feeding motor pattern consists of coupled bursts of the pump dilators and shorter-duration, high-frequency bursts of spikes from the pump compressor. The pump is also activated at the adult molt. At this time, it is used both before the moth emerges from the pupal case for swallowing molting fluid and again after emergence for swallowing air. These behaviors are important for eclosion and are necessary for the expansion of the wings after eclosion. Their motor patterns are similar to the feeding program. Up to 24 h before adult ecdysis, this motor pattern can be triggered by the peptide eclosion hormone. The other eclosion-related peptide, Manduca sexta eclosion-triggering hormone, does not appear to trigger activity of the cibarial pump.

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