DIFFERENT EFFECTS ON RAT ARTERIAL-PRESSURE AND HEART-RATE WHEN LOSARTAN IS INJECTED INTO THE 3RD-VENTRICLE OR 4TH-VENTRICLE

Cardiovascular responses to central losartan (LOS), a non-peptide angiotensin II (ANG II) receptor antagonist, were investigated by comparing the effects of LOS injection into the 3rd and 4th cerebral ventricles (3rdV, 4thV) on mean arterial pressure (MAP) and heart rate (HR). Adult male Holtzman rats were used (N = 6 animals per group). Average basal MAP and HR were 114 +/- 3 mmHg and 343 +/- 9 bpm (N = 23), respectively. LOS (50, 100 or 200 nmol/2 mu l) injected into the 3rdV induced presser (peak of 25 +/- 3 mmHg) and tachycardic (peak of 60 +/- 25 bpm) responses. LOS injected into the 4thV had no effect on MAP, but it induced bradycardia (peak of -35 +/- 15 bpm). KCl (200 nmol/2 mu l) injected into the 3rdV or into the 4thV had no effect on either MAP or HR compared to 0.9% saline injection. The results indicate that LOS injected into the third ventricle acts on forebrain structures to induce its presser and tachycardic effects and that bradycardia, likely dependent on hindbrain structures, is obtained when LOS is injected into the fourth ventricle.

Interaction between areas of the central nervous system in the control of water intake and arterial pressure in rats

1. Water intake induced by injection of 0.2 M-NaCl into the lateral preoptic area was increased by the injection of angiotensin II into the subfornical organ of rats. The injection of hypertonic saline solution into the subfornical organ increased water intake. However, the increase was lower than when the solution was injected into the lateral preoptic area. The injection of 4 μg angiotensin II into the lateral preoptic area further augmented this effect. 2. Injection of angiotensin II into the subfornical organ caused a rise in blood pressure which preceded the thirst-inducing effect. The injection of 0.2 M NaCl into the subfornical organ caused no changes in blood pressure, whereas the injection of angiotensin II into the lateral preoptic area caused some increase. 3. Dehydration of the lateral preoptic area by means of 0.2 M NaCl in combination with intravenous infusion of angiotensin II caused a summation of effects in terms of the water intake, without changing cardiovascular alterations induced by the infusion of angiotensin II. A summation of effects in the water intake, but not in blood pressure, was also observed when 0.5 M NaCl was infused intravenously in combination with the injection of angiotensin II into the subfornical organ and into the lateral preoptic area. 4. The results indicate that there are interactions between the subfornical organ and lateral preoptic area in the regulation of cardiovascular and thirst mechanisms.

Platelet activation in experimental arterial thrombosis.

Platelet aggregates were studied in dogs with induced arterial thrombosis, by the method of Wu and Hoak. Blood was withdrawn from a jugular vein and from the femoral vein on the operated side 24 h after thrombus induction and immediately and 2 h after blood flow was restored by thrombectomy. Platelet activation was significant in dogs with obstructive arterial thrombosis and which tended to subside after thrombectomy. Activation or formation of platelet aggregates seemed to occur in the ischemic limb. It is suggested that this experimental model could be useful to test the action of anti-platelet drugs in vivo.

About the arterial blood vessels pelvic opossum's (Didelphis albiventris) behaviour

The work consists of the study of 20 opossums (Didelphis albiventris); 7 females and 13 males, adults, natives of Jaboticabal county proceeding to a canulation and injection of the arterial system with neoprene latex-650 in the aorta artery (full-blooded). Right away the preparations were fixed by a 10% formaldehyde aqueous solution and afterwards dissected and formed a scheme. The analysis of the pieces showed that in the opossum, the end of the aorta always divides in the common iliac artery, right and left sides, both originating the external and internal iliac artery, on the right and left sides. The medium sacral artery results, medianly, from the aorta division's angle in 2 common iliac arteries in 8 cases (40% - 6 males and 2 females); this vessel comes from the left common iliac artery in 7 animals (35% - 5 males and 2 females) or comes from the right common iliac artery, in 5 preparations (25% - 3 females and 2 males). The deep iliac circumflex artery is born by the common iliac artery from the right side in 10 preparations (50% - 6 males and 4 females), can appear as well, concomitantly with the external and internal iliac artery, from the right side in 9 pieces (45% - 6 males and 3 females) and further from the right this vessels can emerge from the external iliac artery, in 1 case only (5% - 1 male).