Label distribution after injection of labelled tachykinins into the rat lateral cerebroventricle

The present study investigated the label distribution in several brain regions, as well as in the peripheral circulation, following injection of labelled tachykinins [( 3H]-substance P, [3H]-eledoisin or [125I]-neurokinin A) into the lateral cerebroventricle of the rat. A widespread label distribution, extending as far as to the brainstem, was detected. Hypothalamus, striatum and hippocampus were the most labelled regions by the 3 labels; however the patterns of distribution of the 3 labelled tachykinins showed marked differences. Distribution in the brain was rapid, reaching a maximum usually within 2 min after injection and declining slightly afterwards. Large amounts of label (1/6-1/15 of the total amount injected) were detected in serum even at 2 min after injection and increased thereafter, reaching a maximum at 10-15 min.