CHRONIC STIMULATION INCREASES ACETYLCHOLINESTERASE ACTIVITY IN OLD APLYSIA

In the marine mollusc Aplysia, a reduced level of activity of circulat ing AChE (acetylcholinesterase) signals the onset of aging [28], as it does in mammals [23,25]. In old Aplysia, coincident with the reduced AChE activity is impaired neuron function [17], which chronically appl ied sensory stimulation (CSS) improves [35]. As a first step to establ ish the link between the CSS and improved neuronal function, we invest igated if CSS alters the level of AChE activity in old Aplysia. Before and after 4 weeks of CSS of the siphon-gill withdrawal reflex (S/GWR) , we measured circulating and neural levels of AChE and behaviors invo lving the gill in freely moving mature and old Aplysia. Only in old an imals did the CSS produce increased AChE activity levels in both the C NS and serum, and the increased levels were correlates of a change in the S/GWR, the behavior elicited by the CSS. This result shows that ag ing animals are able to up regulate enzymatic activity in response to specific sensory input. It also suggests that age influences how the l evel of AChE activity responds to persistent changes in sensory input. Parallels exist between the results here and those in higher vertebra tes and are discussed.