DISTRIBUTION OF CALMODULIN, CALBINDIN-D28K AND CALRETININ AMONG RAT OLFACTORY NERVE BUNDLES

Calmodulin, calbindin-D28k and calretinin are calcium-binding proteins largely distributed in the bipolar olfactory receptor cells. In the o lfactory epithelium their distribution seemed to be random. Using immu nohistochemistry we have examined their localization in rat olfactory axons extending to the olfactory bulb. Sections were analyzed both hor izontally and vertically. Almost all fibers were immunoreactive for on e of the three intracellular calcium-binding proteins whose distributi on was not random among the bundles. Three different subclasses of fib ers could be detected: calbindin-D28k and calretinin immunoreactivitie s were restricted to external fibers whereas calmodulin immunoreactivi ty was intense, abundant and largely distributed throughout the intern al portion of the olfactory nerve. This additional degree of organizat ion detected in the olfactory axons might play a role in odor discrimi nation.