7-OH-DPAT, unlike quinpirole, does not prime a yawning response in rats

Repeated treatment in ontogeny with the dopamine (DA) D(2)/D(3) receptor agonist quinpirole is associated with enhanced quinpirole-induced yawning and other behaviors such as vacuous chewing, vertical jumping, and antinociception. To determine if the reputedly DA D(3) agonist (+/-)-2-(dipropylamino)-7-hydroxy-1,2,3, 4-tetrahydronaphthalene (7-OH-DPAT) would prime for yawning in a manner analogous to that for quinpirole, rats were treated for the first 11 days after birth with an equimolar dose of either quinpirole or 7-OH-DPAT (195.4 nmol/kg/day) and tested for agonist-induced yawning in adulthood. While enhanced quinpirole-induced and 7-OH-DPAT-induced yawning was observed in quinpirole-primed rats, acute treatments with quinpirole and 7-OH-DPAT did not produce an enhanced yawing response in 7-OH-DPAT-"primed" rats. Our findings indicate that 7-OH-DPAT, unlike quinpirole, does not prime for quinpirole- or 7-OH-DPAT-induced yawning in rats.