2.7 Blood pressure measurements in conscious rats
The day before blood pressure measurements, 8-12 weeks old male Wistar rats were anesthetized by ketamine/xylazine (60 mg kg-1 / 9 mg kg-1, respectively,i.p ). A polyethylene cannula was inserted into the abdominal aorta through the femoral artery for blood pressure measurements and another cannula was inserted into the inferior cava vein through the femoral vein or in the aorta through the left common carotid artery for intravenous (i.v. ) or intraarterial (i.a ) administration, respectively, of BK-(1-9) and its fragments. The cannulas, filled with saline and closed by metallic pins, were exteriorized in the interscapular region of the animals’ backs. Rats were individually housed and left to recover for 24 hours. On the following day, rats were coupled to a pressure transducer and then allowed to stabilize until cardiovascular parameters were stable. The cardiovascular parameters were recorded using the MP 150 Biopac System (Goleta, CA, USA). First, a dose-response relationship was obtained to assess whether BK-(1-9) and its fragments were able to elicit biological responses in vivo. In order to do so, BK-(1-9), BK-(1-7) or BK-(1-5) was administered i.v. as a bolus (0.1 mL), corresponding to a dose of 2.5 nmol, 5 nmol or 10 nmol per animal, in sterile saline. Sterile saline was injected at the same volume, as vehicle control. To further explore the in vivo effect mediated by BK-(1-9) and its related fragments, a bolus (0.1 mL) of each peptide was administered, corresponding to a dose of 10 nmol per animal, in the arterial or venous circulation of adult male rats to assess whether passage through the pulmonary vascular beds would alter the response to these peptides. We also decided to test whether in vivo inhibition of ACE would affect the responses to BK-(1-9), BK-(1-7) and BK-(1-5). After i.v. administration of captopril (5mg kg-1, in sterile saline) and stabilization of cardiovascular parameters, animals were given BK-(1-9) or its related peptides (0.1 mL, 10 nmol per animal, in sterile saline).