Volume 17, Number 17,
Issue of September 1, 1997
pp. 6629-6638
Copyright ©1997 Society for Neuroscience
Developing Neonatal Rat Sympathetic and Sensory Neurons Differ in
Their Regulation of 5-HT3 Receptor Expression
Received March 24, 1997; revised June 18, 1997; accepted June 23, 1997.
Madelaine Rosenberg,
Brigitte Pié, and
Ellis Cooper
Department of Physiology, McGill University, Montréal,
Québec, Canada H3G 1Y6
Serotonin 5-HT3 receptors (5-HT3Rs) are
ligand-gated ion channels expressed by many peripheral neurons and are
involved in several physiological processes. To learn more about the
developmental regulation of 5-HT3R expression, we
investigated rat sympathetic and vagal sensory neurons. We found that
sympathetic and sensory neurons differ in their regulation of
5-HT3R expression during early postnatal life and as these
neurons develop in culture. In SCG neurons 5-HT3R
transcript levels are low at postnatal day 1 (P1) and increase 7.5-fold
by P21; this increase occurs even after elimination of preganglionic
innervation. In comparison, 5-HT3R mRNA levels in P1 nodose
neurons are over 14-fold greater than in P1 SCG and change little by
P21. We show that 5-HT3R transcript levels in nodose
neurons depend on intact target innervation and drop by 60% after
axotomy. When P1 SCG neurons develop in culture, we observed a
significant increase in 5-HT3R expression: after 7 d
in culture, transcript levels increase ninefold versus a threefold increase for neurons developing for 7 d in vivo. In
contrast, 5-HT3R mRNA levels in cultured nodose neurons
drop by 70% within 24 hr; however, this drop is transient. After
2 d, transcript levels begin to increase, and after 7 d, they
are above initial values. We show that this delayed increase in
5-HT3R expression depends on neurotrophins. In both nodose
and sympathetic neurons we found that the changes in 5-HT3R
gene expression correlate directly with the appearance of 5-HT-evoked
current densities.
Key words:
5-HT3 receptor;
ligand-gated ion channel;
sympathetic;
superior cervical ganglion;
sensory;
nodose;
trigeminal;
mRNA expression;
neurotrophins;
axotomy