ORIGINAL ARTICLESBehavioral characterization of serotonergic activation in the flatworm PlanariaFarrell, Martilias S.; Gilmore, Kirsti; Raffa, Robert B.; Walker, Ellen A. Author Information Department of Pharmaceutical Sciences, Temple University School of Pharmacy, Philadelphia, Pennsylvania, USA Correspondence to Ellen Walker, PhD, Department of Pharmaceutical Sciences, Temple University School of Pharmacy, 3307 North Broad Street, Philadelphia, PA 19140, USA E-mail: [email protected] Received 12 September 2007 Accepted as revised 29 January 2008 Behavioural Pharmacology: May 2008 - Volume 19 - Issue 3 - p 177-182 doi: 10.1097/FBP.0b013e3282fe885e Buy Metrics Abstract Serotonin (5-hydroxytryptamine, 5-HT) receptors have been identified in Planaria, a model used for studying the pharmacology of behavioral phenomena. This study characterized the behavioral and locomotor effects of 5-HT, a 5-HT1A agonist, a 5-HT1B/2C agonist, and a 5-HT1A antagonist to examine the role of 5-HT receptor activation in this species. Planarians were video recorded individually in a clear plastic cube containing drug solution or vehicle. To quantify locomotor velocity (pLMV), planarians were placed individually into a dish containing drug solution or vehicle and the rate of gridline crossings was recorded. For the antagonist experiments, four conditions were studied: water alone, agonist alone, antagonist alone, and agonist plus antagonist. The decrease in pLMV induced by the5-HT1A agonist (8-OH-DPAT), and the 5-HT1B/2C agonist (mCPP), was antagonized by pretreatment with the 5-HT1A antagonist (WAY-100635) at a dose that had no effect of its own on pLMV. At a higher concentration of WAY-100635, further decreases in pLMV induced by 8-OH-DPAT were observed. Each agonist produced increased occurrences of ‘C-like position’ and ‘screw-like hyperkinesia’, 5-HT and mCPP produced ‘writhing’, and only mCPP produced a significant increase in duration of ‘headswing’ behavior. The results demonstrate that the 5-HT1A receptor identified in Planaria mediates behavioral responses to 5-HT receptor ligands, supporting the notion that planarians possess functional 5-HT receptors and might serve as a simple model for their study. © 2008 Lippincott Williams & Wilkins, Inc.