Guanethidine

Tissues used for imaging and electrophysiological experiments were perfused with KRB solution containing (mM): NaCl, 120.35; KCl, 5.9; NaHCO₃, 15.5; NaH₂PO₄, 1.2; MgCl₂, 1.2; CaCl₂, 2.5; and glucose, 11.5. KRB solution was oxygenated with a mixture of 97% O₂/3% CO₂ and warmed to 37°C. For experiments using 0 mM [Ca²⁺]_o, CaCl₂ was excluded from the KRB solution and 0.5 mM EGTA was added, resulting in a Ca²⁺ free KRB solution. Ca²⁺ free Hanks’ solution contained the following (mM): NaCl, 125; KCl, 5.36; Glucose, 10; Sucrose, 2.9; NaHCO₃, 15.5; KH₂PO₄, 0.44; Na₂HPO₄, 0.33; Hepes, 10. The pH was adjusted to 7.4 with NaOH.
Nifedipine, nicardipine, atropine, guanethidine, L-NNA, CPA, tetracaine, caffeine, EGTA, and GSK 7975A were purchased from Sigma-Aldrich (St. Louis, MO, USA). Ani9 and MRS2500 was purchased from Tocris Bioscience (Ellisville, Missouri, USA). TTX was purchased from Abcam (Cambridge, MA, USA). Atropine, guanethidine, L-NNA, MRS2500, TTX, CPA, tetracaine and caffeine were diluted in deionized water. Nifedipine and nicardipine were diluted in ethanol. Ani9 was diluted in DMSO. All stock solutions of drugs were diluted to the desired final concentrations with KRB solution.