The mechanisms of action of antihypertensive drugs

Augmentation of immune cell activity against tumor cells by Rauwolfia radix

In this study, we investigated the effect of Rauwolfia radix on heat shock protein (HSP) 70 expression and cytotoxicity against tumor cells in activated human T cells. When activated T cells were cultured with Rauwolfia radix for 18 h, HSP70 expression after heat shock was remarkably increased, and cytotoxicity against T98G tumor cells was augmented. Moreover, Rauwolfia radix also enhanced the cytotoxicity of heat shocked activated T cells against Molt-4 and T98G tumor cells. Secretions of interferon-gamma (IFN-gamma) and tumor necrosis alpha (TNF-alpha), due to Concanavalin A (Con A) stimulation, were increased by Rauwolfia radix in activated T cells. To investigate the antitumor effect in vivo, EL-4 tumor-bearing mice were administered with Rauwolfia radix in drinking water. The survival period of the Rauwolfia radix treatment group was significantly prolonged compared with that of the control group. Reserpine, the major active ingredient of Rauwolfia radix, also enhanced the cytotoxicity of activated T cells against Molt-4 and T98G tumor cells, and prolonged the survival period of EL-4 tumor-bearing mice. Taken together, our results suggest that Rauwolfia radix can enhance the activity of immune cells against tumor cells.

Centrally induced hypotensive effects of beta-adrenergic blocking drugs

The mechanism of the antihypertensive effects of propranolol, pindolol and sotalol were investigated using chloralose-anesthetized cats and dogs. When administered i.v. into a carotid or vertebral artery, propranolol was readily taken up by several brain areas. Highest drug concentrations were detected in the hypothalamus and its projection areas and low concentrations in the cerebral cortex and peripheral tissues. Discrete drug administration at several brain sites decreased efferent sympathetic but increased efferent parasympathetic nerve activity. These neural changes were associated with reductions in both blood pressure and heart rate. Hippocampal propranolol administration induced the greatest neural and cardiovascular changes. Significant concurrent reductions in blood pressure, heart rate and cardiac contractile force occurred following propranolol (500 mug) administration into the hippocampus and pindolol (80 mug) administration into the septum. Sotalo injections at various brain sites failed to influence the cardiovascular system. The centrally induced cardiovascular and neural changes induced by both propranolol and pindolol were prevented by pretreatment with hexamethonium. These results suggest that the hypotensive effects of both propranolol and pindolol may be related to a reduction in the level of central autonomic control resulting in decreased levels of blood pressure, heart rate and cardiac contractile force.