Sensory input and central excitation and inhibition in the blowfly.

Abstract

A water-satiated fly does not extend its proboscis when water touches a labellar hair. However, if another labellar hair is stimulated by sucrose directly prior to water stimulation, water stimulation causes proboscis extension. This induced responsiveness to water reflects a perseverating central nervous system excitatory state (CES) which decays slowly in time; its intensity and decay rate are a function of concentration of sucrose stimulation and degree of food deprivation, but not of crop distension, blood sugar level, or ingestion of sucrose. The finding that water stimulation and salt stimulation discharge central excitatory states until further sucrose stimulation occurs reveals a methodological problem in studying perseveration of central inhibitory states. A neural model is presented to account for the findings.