Sensitivity of neonatal rabbit ileum to histamine

Segments of ileum from newborn rabbits contracted in response to histamine but sensitivity declined from age 11 days. Intestine from adult animals barely contracted to histamine, even in a concentration of 3 times 10- minus 3 M. Such variation with age was not observed with acetylcholine. The response to histamine was effected by mepyramine-sensitive receptors which appeared to decrease in number as the animals aged.