Journal of Neuroscience, Vol 7, 391-399, Copyright © 1987 by Society for Neuroscience
Evidence for serotonin synthesis, uptake, and release in dissociated rat sympathetic neurons in culture
DW Sah and SG Matsumoto
In the previous paper (Matsumoto et al., 1987), pharmacological evidence
for secretion of serotonin (5-HT) by cultured sympathetic principal neurons
was reported. Here, we present further evidence that 5-HT is a transmitter
of some of these neurons under certain culture conditions, and can also be
a "false" transmitter. Sympathetic principal neurons, dissociated from
superior cervical ganglia (SCG) of newborn rats, were grown in cell
culture. The presence of serotonin was demonstrated with high-performance
liquid chromatography (HPLC), immunocytochemistry, and electrophysiological
recording. Homogenates of cultures contained a substance that comigrated
with authentic 5-HT in HPLC. A voltammogram for this substance was
superimposed upon that for authentic 5-HT. When the cultures were examined
with immunocytochemical staining, using the peroxidase-antiperoxidase
technique, many neuronal processes contained 5-HT-like immunoreactive
material. Many somata also contained 5-HT-like immunoreactivity when the
neurons were grown in the presence of medium conditioned by heart cells
(CM), but few somata stained above background in the absence of CM. Medium
that contained a raised concentration of K+ (54 mM) or veratridine evoked
Ca2+-dependent release of 5-HT, consistent with a neurotransmitter role for
5-HT in the cultures. In preliminary electrophysiological experiments on
microcultures containing single sympathetic principal neurons and cardiac
myocytes, a nonadrenergic excitatory (NAE) interaction was sometimes
obtained after exposing the neurons to 100 microM 5- hydroxytryptophan.
This interaction was sensitive to the serotonin blockers reserpine,
methysergide, and gramine.(ABSTRACT TRUNCATED AT 250 WORDS)