Dopamine D₁ and D₂ effects on fetal mouthing responses to milk

Abstract

Rat fetuses exhibit prompt responses to an intraoral infusion of milk, including mouthing movements and an increase in motor activity. Two experiments examined the involvement of dopamine D₁ and D₂ receptors in mediating these fetal responses to milk. The D₁ agonist SKF-38393 and the D₂ antagonist sulpiride diminished fetal mouthing responses. Mouthing responses appeared normal in fetuses treated with the D₂ agonist quinpirole or the D₁ antagonist SCH-23390. These findings suggest that activity in the dopamine system may inhibit mouthing within 30 s of milk infusion.