The D3-receptor agonist (±)-7-hydroxy-N,N-di-n-propyl-2-aminotetralin (7-OH-DPAT) attenuates morphine-induced hyperlocomotion in mice

The effects of the D 3 -agonist (±)-7-hydroxy- N,N -di-n-propyl-2-aminotetralin (7-OH-DPAT) on morphine-induced hyperlocomotion were investigated in mice. 7-OH-DPAT (0.01-0.3 mg/kg s.c.) alone did not produce a significant locomotor activity in mice. Treatment with low doses of 7-OH-DPAT (0.1 and 0.3 mg/kg s.c.) attenuated morphine (10 and 20 mg/kg s.c.)-induced hyperlocomotion. The significant morphine-induced increase in dopamine (DA) metabolite levels, 3,4-dihydroxyphenylacetic acid and homovanillic acid in the limbic forebrain (nucleus accumbens and olfactory tubercle) was suppressed by 7-OH-DPAT. These results suggest that activation of the D 3 -receptor in the mesolimbic dopamine system may attenuate the expression of morphine-induced hyperlocomotion.