Dmt 510

During the isolated heart experiments, after thoracotomies performed under ketamine/xylazine anaesthesia, the brain was removed and placed into a silicone containing petri dish, filled with 0–4 °C Krebs solution (composition in mmol: 110 NaCl, 5.0 KCl, 1.0 MgSO₄, 1.0 KH₂PO₄, 5.0 glucose and 24.0 NaHCO₃, obtained from Sigma-Aldrich, St. Louis, MO, USA). The solution was equilibrated previously with a gaseous mixture of 5% CO₂, 10% O₂ and 85% N₂ at pH 7.4. Basilar arteries were isolated with microsurgical tools (Fine Science Tools GmbH, Heidelberg, Germany). The arteries were equally cut into 4 mm long rings, which were then mounted in an isometric contraction measurement system (DMT-510, Danish Myotechnology, Aarhus, Denmark). The Ca²⁺-free Krebs solution was changed to Ca²⁺-containing one (composition in mM: 110 NaCl, 2.5 CaCl_2, 5.0 KCl, 1.0 MgSO₄, 1.0 KH₂PO₄, 5.0 glucose and 24.0 NaHCO₃, obtained from Sigma-Aldrich, St. Louis, MO, USA). Before every experiment, a normalization protocol was performed, by stretching the preparations with 1.5 mN force, which was increasing evenly every 15 s until the calculated intraluminar pressure reached 13.4 kPa. The experiments were then performed at this stretch level. Contractile responses for KCl (6–66 mM), serotonine (1 nM–10 μM) and angiotensin II (1 nM–100 μM) have been recorded.