Calmodulin, calbindin-D28k, calretinin and neurocalcin in rat olfactory bulb during postnatal development.

Odorant stimulation of receptor cells results in a calcium influx that activates the transduction pathway. The olfactory neurons extend axons to the olfactory bulb where they synapse onto mitral cells. Ca(2+)-acceptors also may participate in subsequent processing of olfactory information. The present study describes the distribution of calmodulin, calretinin, calbindin-D28k and neurocalcin during rat main olfactory bulb development. From postnatal day 1 (P1) we observed in the olfactory nerve layer a thin external bundle containing calbindin and calretinin whereas calmodulin was present in a large internal bundle. In tufted cells, neurocalcin immunoreactivity was detected at P10 and increased until P20. In mitral cells calmodulin was intensively immunoreactive at P1 but decreased during development to disappear at adulthood whereas calretinin was weakly labelled at P1 but raised in intensity until P20. In granule cells calbindin-D28k and calretinin were detected from P1. Giant neurons were positive for both calretinin and calbindin-D28k from postnatal day 20.