Drug Application.

Drugs were diluted in aCSF and applied either through whole-chamber perfusion (for antagonists) or by pressure ejection through a drug delivery glass pipette positioned about 10 to 20 μm away from the target cell upstream of the aCSF flow (for agonists). The puffs were triggered and controlled by stimulation protocols programmed using PatchMaster software (HEKA Instruments). The puff duration was 30 ms, and the air pressure ranged between 5 and 30 psi. During the drug ejection, the recording chamber was continuously perfused with aCSF or aCSF containing the desired antagonists.