Blood pressure control by the renin-angiotensin system and its interaction with the sympathetic nervous system in fish.

The renin-angiotensin system (RAS) is from an evolutionary viewpoint a well-preserved regulatory system with many morphological and physiological similarities in all vertebrate groups from fish to mammals. Regulation by the RAS is often complicated, involving several other control systems and blood pressure is just one of many parameters controlled by this system. Control of cardiovascular functions by the RAS in fish has received some attention and both a direct action and modulation of adrenergic nerves by angiotensin II have been reported in most species studied. The interaction between the RAS and the adrenergic system in fish is not fully understood, but the facilitation of catecholamine release by angiotensin II is probably one of the more important mechanisms.