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Keywords:

  • dopamine receptor subtypes;
  • D5 knockout mice;
  • ethogram;
  • grooming behaviour;
  • seizures

Abstract

The phenotypic ethogram of congenic dopamine D5 receptor “knockout” mice was evaluated. Each individual topography of behaviour within the natural repertoire was assessed over the extended course of initial exploration of and subsequent habituation to the environment, and following challenge with a series of D1-like agonists. Over initial exploration, D5-null mice evidenced a modest reduction in locomotion and a modest increase in sifting. Subsequent habituation revealed additional phenotypic effects, primarily overall reduction in grooming and delayed habituation of rearing. Among D1-like agonists, A 68930 stimulates both adenylyl cyclase and a putative D1-like receptor coupled to stimulation of phospholipase C-mediated phosphoinositide hydrolysis; conversely, SK&F 83959 stimulates phosphoinositide hydrolysis but not adenylyl cyclase while SK&F 83822 stimulates adenylyl cyclase but not phosphoinositide hydrolysis. Though programmed grooming syntax and episodic seizure activity induced by A 68930 and SK&F 83822 were unaltered, grooming induced by SK&F 83959 was reduced in D5 mutants. Stereotyped, ponderous locomotion induced by the D2-like agonist RU 24213 was enhanced in D5 mutants. Phenotypic and pharmacological characterisation of congenic D5-null mice at an ethological level identifies novel functional roles for the D5 receptor in mediating discrete topographies of behaviour relating to exploration, sequential motor coordination, and how these processes change over the course of interaction with and habituation to the environment. Additionally, they indicate the involvement of phosphoinositide hydrolysis and D5:D2-like interactions in regulating these processes. Synapse 55:201–211, 2005. Published 2005 Wiley-Liss, Inc.