Yukio Fujino and Tomoko Fujii
Department of Pharmacology, Teikyo University School of Medicine, 2-11-1
Kaga, Itabashi-ku, Tokyo 173, Japan
Abstract: In the previous study, we have demonstrated that nicotine
hardly induces catecholamine release from adrenal medulla of 21-day-old
rats. The present study examined the responsiveness of the adrenal chromaffin
cells to acetylcholine in vitro and neostigmine and oxotremorine in vivo
in 21-day-old and 8-week-old rats. As assessed by electron microscopy, the
number of the chromaffin granules was markedly decreased and the content
of adrenaline in adrenals was diminished significantly by oxotremorine treatment
in 8-week-old rats, whereas these changes did not occur in 21-day-old rats.
Morphological changes of the adrenal chromaffin cells, with respect to exocytosis,
were not observed in neostigmine-treated 21-day-old rats and acetylcholine-treated
adrenal slices prepared from 21-day-old rats. Catecholamine release was
hardly evoked by acetylcholine in these slices as judged by measuring the
catecholamine content in the medium. These results indicate that the sensitivity
of the chromaffin cells to these secretagogues in 21-day-old rats is very
low when compared to that in young adult rats.
Keywords: Acetylcholine, Adrenal chromaffin cell, Oxotremorine, Catecholamine
release, Infant rat