Propranolol can Inhibit the Development of Hypertension in SHR

The ability of propranolol, a beta-adrenergic blocking agent, to decrease blood pressure and inhibit the development of hypertension was assessed in spontaneously hypertensive rats (SHR). Oral propranolol was administered via drinking water to SHR and age matched normotensive control (WKY) groups beginning at conception, birth, three, six, or nine weeks of age. Controls for all groups were given tap water. Propranolol treatment was withdrawn from all groups at twelve weeks of age. A comparison of developmental parameters such as water consumption, weight gain and survival showed no differences between SHR and WKY or between SHR with propranolol vs WKY with propranolol. Systolic blood pressures and heart rates were monitored non-invasively from seven to sixteen weeks of age. There was a variable reduction in SHR blood pressures during propranolol treatments starting at 6 weeks of age or earlier, but when propranolol treatment was withdrawn, SHR blood pressures increased as did SHR without propranolol treatment. In SHR offspring who were exposed to propranolol through fetal and neonatal development and whose sires and dams were pretreated with propranolol, the development of high blood pressure was inhibited. Blood pressures indicated that this group did not develop hypertension for up to four weeks after propranolol was withdrawn even though heart rate returned to normal. Based upon these findings, a critical period during SHR development was defined during which development of hypertension can be inhibited by propranolol.