Pd 168 077 maleate

Extracellular solution used as a control bath for dissection and whole cell recordings was bubbled with a mixture of 95% O2-5% CO2, which set the pH to ~7.4 and contained the following (in mM): 125.00 NaCl, 2.50 KCl, 1.00 MgCl2, 1.25 NaH2PO4, 20.00 glucose, 26.00 NaHCO3, and 2.00 CaCl2. The intracellular solution in the recording pipette used for monitoring inhibitory rod bipolar cell currents contained the following (in mM): 120.00 CsOH, 120.00 gluconic acid, 1.00 MgCl2, 10.00 HEPES, 10.00 EGTA, 10.00 tetraethylammonium-Cl, 10.00 phosphocreatine-Na2, 4.00 Mg-ATP, 0.50 Na-GTP, and 0.1% sulforhodamine-B dissolved in water and was adjusted to pH 7.2 with CsOH. With these concentrations, the driving force for Cl-was calculated as 60 mV in all solutions. The D4 agonist PD-168077-maleate (PD, 500 nM; Sigma) was used to selectively activate D4 receptors. This drug was diluted in extracellular solution to the given concentration and applied to the bath during the recordings by a gravitydriven superfusion system (Cell Microcontrols, Norfolk, VA) at a rate of ~1 ml/min. As DMSO was initially used to solubilize the drug, our perfusate had a final working DMSO concentration of less than 0.0025% by mass. Chemicals were purchased from Sigma-Aldrich (St. Louis, MO), unless otherwise indicated.