Dopamine D₂-like receptor binding in the brain of male Japanese quail (Coturnix japonica)

Japanese quail (Coturnix japonica) have been used extensively to study appetitive behaviors. However, little is known about the appetitive-relevant neurochemical systems in this species. The present investigation examined the distribution of D₂-like dopamine receptors in the quail brain. [³H]Spiperone was incubated in brain tissue homogenates and non-specific binding was defined using (-)-sulpiride. Scatchard analysis of whole brain without cerebellum and forebrain alone indicated approximate K(d)'s of 0.08 and 0.04 nM, respectively. In addition, the preferential D₃ agonist (±)-2-dipropylamino-7-hydroxy-1,2,3,4-tetrahydronaphthalene hydrobromide (7-OH-DPAT) did not displace [³H]spiperone binding in quail forebrain. Finally, regional analysis showed that the highest densities of D₂-like receptors were located in the forebrain. Overall, these results indicate that there is some conservation of dopaminergic mechanisms between aves and mammals. Thus, Japanese quail may be useful for examining the neuropharmacological mechanisms of dopaminergic stimulant drugs that work via D₂-like receptor activation. (C) 2000 Elsevier Science Ireland Ltd.