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Updated: Aug 8, 2026

Planarian Scrunching as a Quantitative Behavioral Readout for Noxious Stimuli Sensing
Published on: July 30, 2020
Schild (apparent pA2) analysis of a kappa-opioid antagonist in Planaria
Robert B Raffa1, David A Baron, Ronald J Tallarida
1Department of Pharmaceutical Sciences, Temple University School of Pharmacy, 3307 N. Broad Street, Philadelphia, PA 19140, USA. robert.raffa@temple.edu
Abstract:
Previous investigators have provided radioimmunological and immunocytochemical evidence for an enkephalinergic (opioid) system in Planaria and described naloxone-sensitive qualitative behavioral responses to kappa-opioid receptor agonists. We report the application of Schild-analysis to the antagonism of a selective kappa agonist (U-50,488H) by a selective kappa antagonist (nor-BNI) in a quantitative in vivo endpoint. The results provide further evidence of a kappa-opioid-like receptor in planarians.
