Ontogenetic quinpirole treatment produces long-lasting decreases in the expression of Rgs9, but increases Rgs17 in the striatum, nucleus accumbens and frontal cortex


Dr Russell W. Brown, as above.
E-mail: brown1@mail.etsu.edu


Ontogenetic treatment of rats with the dopamine D2-like receptor agonist quinpirole produces a significant increase in dopamine D2 receptor sensitivity that persists throughout the animal's lifetime, a phenomenon known as D2 priming. The present study was designed to investigate the effects of priming of the D2 receptor on the expression of three different members of the regulator of G-protein signaling (RGS) family: Rgs4, Rgs9 and Rgs17. Male offspring were ontogenetically treated with quinpirole or saline from postnatal days (P)1–21 and raised to adulthood. On ∼ P65, animals were given an acute quinipirole injection (0.1 mg/kg) and the number of yawns was recorded for 1 h after the injection. Yawning has been shown to be a behavioural event mediated by the dopamine D2/D3 receptor. Animals ontogenetically treated with quinpirole demonstrated a significant 2.5-fold increase in yawning as compared to controls. Rgs transcripts were analysed through in situ hybridization several weeks later. Rats ontogenetically treated with quinpirole demonstrated a significant decrease in Rgs9 expression in the frontal cortex, but a more robust decrease in the striatum and nucleus accumbens as compared to controls. Regarding Rgs17, ontogenetic quinpirole produced a modest but significant increase in expression in the same brain areas. There were no significant differences in Rgs4 expression produced by drug treatment in any of the brain regions analysed. This study demonstrates that ontogenetic quinpirole treatment, which results in priming of the D2 receptor, results in significant decreases in Rgs9, which has been shown to regulate G-protein coupling to D2 receptors.