Differential effects of dopamine D1 and D2 agonists and antagonists on velocity of movement, rearing and grooming in the XXXX . Implications for the roles of D1 and D2 receptors.

@entity49358 @entity10095 @entity19 @entity3826 @entity1767 @entity4944 @entity2344
A system combining visual recording of rearing and grooming, with automatic measurement of slow and fast components of locomotion, was examined for its suitability as a means of studying the effects on behaviour of conventional and novel dopaminergic drugs in the @entity19 . @entity4944 (0.1-10 mg/kg) selectively stimulated fast movements and affected rearing bimodally. @entity3826 (0.01-5 mg/kg) influenced locomotion polyphasically, depressing fast movements and enhancing slow ones, and producing parallel changes in rearing. Both drugs reduced grooming monotonically. A dose of @entity3826 (25 micrograms/kg) which is considered to act presynaptically produced @entity1767 -resistant sedation, while a larger dose (0.5 mg/kg; with postsynaptic actions) evoked head-down sniffing and ponderous walking that were partially prevented by pretreatment with 0.05 mg/kg @entity1767 (D2 blocker), but not 0.01 mg/kg @entity10095 (D1 blocker). The behavioural effects of @entity1767 (0.2-0.4 mg/kg) and @entity10095 (0.05 mg/kg) were indistinguishable; both drugs caused sedation and inhibited all forms of motor activity. Small doses of @entity10095 (2-10 micrograms/kg) and large doses of the D1 agonist @entity2344 (3-10 mg/kg) evoked excessive grooming. The drug @entity2344 (1-30 mg/kg) had no other effects on motor behaviour, whereas the whole spectrum of pre- and postsynaptic motor responses produced by @entity3826 could be duplicated with the D2 agonist @entity49358 (0.05-15 mg/kg). The differential sensitivity of fast and slow components of locomotion to treatment with drug suggests these are qualitatively distinct responses. The results implicate D2 receptors in the mechanisms of locomotion and rearing, and D1 receptors in the expression of grooming.
