BEHAVIORAL-ASSESSMENT OF MICE LACKING D-1A DOPAMINE-RECEPTORS

Dopamine D-1A receptor-deficient mice were assessed in a wide variety of tasks chosen to reflect the diverse roles of this receptor subtype in behavioural regulation. The protocol included examination of explor ation and locomotor activity in an open field, a test of sensorimotor orienting, both place and cue learning in the Morris water maze, and a ssessment of simple associative learning in an olfactory discriminatio n task. Homozygous mice showed broad-based impairments that were chara cterized by deficiencies in initiating movement and/or reactivity to e xternal stimuli. Data obtained from flash evoked potentials indicated that these deficits did not reflect gross visual impairments. The part ial reduction in D-1A receptors in the heterozygous mice did not affec t performance in most tasks, although circumscribed deficits in some t asks were observed (e.g., failure to develop a reliable spatial bias i n the water maze). These findings extend previous behavioural studies of null mutant mice lacking D-1A receptors and provide additional supp ort for the idea that the D-1A receptor participates in a wide variety of behavioural functions. The selective impairments of heterozygous m ice in a spatial learning task suggest that the hippocampal/cortical d opaminergic system may be uniquely vulnerable to the partial loss of t he D-1A receptor. (C) 1998 IBRO. Published by Elsevier Science Ltd.