The distribution of angiotensin II binding sites in rodent brain.

The distribution of specific angiotensin II (AII) binding capacity of several brain regions, pituitary, and adrenals was determined in 6 rodent species namely rats, mice, hamsters, kangaroo rats, gerbils and degus. Rats and mice had similar distributions with the highest levels of binding observed in the area postrema, septum and superior colliculi. Low levels were seen in the cortex, cerebellum, striatum and hippocampus. Other areas had intermediate levels. The distribution of AII binding in gerbils and degus was strikingly different from rats and mice. In these species, little or no binding could be detected in the brain. Additionally, the level of binding in degu adrenals was extremely low when compared to the binding observed in the adrenals of the other species. The distribution of AII binding sites in hamsters and kangaroo rats, although similar in some ways to rats and mice, had several major differences. Both had much higher levels of specific binding in cerebellum, striatum, and the hippocampus areas which had low levels of AII binding in rats an mice. Hamsters were the only species to exhibit significant specific binding in the cortex. The kangaroo rats had an unusual distribution of receptors with an apparent lack of specific binding in midbrain and area postrema.