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This Article Full Text Full Text (PDF) All Versions of this Article: 99/6/2844    most recent 00986.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Spitzer, N. Articles by Baro, D. J. PubMed PubMed Citation Articles by Spitzer, N. Articles by Baro, D. J.

Serotonin Transduction Cascades Mediate Variable Changes in Pyloric Network Cycle Frequency in Response to the Same Modulatory Challenge

¹Department of Biology and ²Department of Physics and Astronomy, Georgia State University, Atlanta, Georgia

Submitted 3 September 2007; accepted in final form 27 March 2008

A fundamental question in systems biology addresses the issue of how flexibility is built into modulatory networks such that they can produce context-dependent responses. Here we examine flexibility in the serotonin (5-HT) response system that modulates the cycle frequency (cf) of a rhythmic motor output. We found that depending on the preparation, the same 5-min bath application of 5-HT to the pyloric network of the California spiny lobster, Panulirus interruptus, could produce a significant increase, decrease, or no change in steady-state cf relative to baseline. Interestingly, the mean circuit output was not significantly different among preparations prior to 5-HT application. We developed pharmacological tools to examine the preparation-to-preparation variability in the components of the 5-HT response system. We found that the 5-HT response system consisted of at least three separable components: a 5-HT_2βPan-like component mediated a rapid decrease followed by a sustained increase in cf; a 5-HT_1Pan-like component produced a small and usually gradual increase in cf; at least one other component associated with an unknown receptor mediated a sustained decrease in cf. The magnitude of the change in cf produced by each component was highly variable, so that when summed they could produce either a net increase, decrease, or no change in cf depending on the preparation. Overall, our research demonstrates that the balance of opposing components of the 5-HT response system determines the direction and magnitude of 5-HT–induced change in steady-state cf relative to baseline.