Behavioural effects of the dopamine D3 receptor agonist 7-OH-DPAT in rats

The putative selective dopamine (DA) D3 receptor agonist, 7-OH-DPAT (25-4000 micrograms kg-1), enhanced stretching-yawning and penile erection in male rats, besides respectively increasing and decreasing sedation at low (25-200 micrograms kg-1) and high (1600 and 4000 micrograms kg-1) doses and inducing stereotypy from 800 micrograms kg-1 upwards. The DA D2 antagonist, (-) eticlopride (10 and 20 micrograms kg-1), antagonized stretching-yawning and penile erection induced by a low dose of 7-OH-DPAT (50 micrograms kg-1) but not those produced by high doses (1600 and 4000 micrograms kg-1), when stereotyped behaviour, on the other hand, was potently inhibited. Comparative experiments performed with the DA agonist SND 919 gave similar results.