Essential conservation of D1 mutant phenotype at the level of individual topographies of behaviour in mice lacking both D1 and D3 dopamine receptors

Rationale. In the absence of agonists and antagonists evidencing appropriate selectivities, individual and interactive properties of D₁ and D₃ dopamine receptors would be illuminated most powerfully by their co-deletion. Objectives. To define and contrast the behavioural phenotype of D₁/D₃ double knockout mice in comparison with wild types, and with individual D₁ and D₃ mutants. Methods. Behavioural phenotype was characterised using an ethologically based topographical technique. Results. On comparison with wild types, D₁/D₃ double mutants were characterised topographically as follows: increases in sniffing and locomotion, which evidenced delayed habituation; reductions in rearing free, rearing seated, grooming, chewing and stillness. Though the D₁/D₃ double mutant ethogram comprised elements of both single mutant D₁ and D₃ lines, this phenotype was largely reflective of the D₁ mutant component. Conclusions. Distinct patterns of initial exploratory behaviour and of temporal change over subsequent habituation were evident across the three genotypes, with particular conservation of the D₁ phenotype in D₁/D₃ double mutants. Under the present conditions, there was little systematic evidence for D₁:D₃ interactions in the regulation of these aspects of behaviour. Electronic Publication