The relationship between the expression of calretinin and the maturati
on level of peripheral sensory neurons was investigated by means of im
munohistochemistry and immunoblot analysis. Our immunohistochemical re
sults show that calretinin is expressed during two different developme
ntal phases in rat dorsal root ganglia. The early phase lasts between
embryonic days 11 and 14, when calretinin is detectable in the majorit
y (75%) of the cells. A second phase starts at embryonic day 17 and la
sts throughout the whole postnatal life, when calretinin is expressed
only in a small proportion of the neurons (less than 8%). Between thes
e two periods no calretinin is found in the ganglia. These changes in
calretinin expression during embryonic development were confirmed by W
estern blot analysis. The early expression of calretinin in dorsal roo
t ganglion cells suggests that calretinin may act as a calcium regulat
or until neurotrophins take over the precise tuning of intracellular c
alcium concentration. (C) 1998 Elsevier Science B.V.