Journal of Neuroscience, Vol 11, 600-607, Copyright © 1991 by Society for Neuroscience
Distribution of GAP-43 mRNA in the brain stem of adult rats as evidenced by in situ hybridization: localization within monoaminergic neurons
C Bendotti, A Servadio and R Samanin
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
Using in situ hybridization, we examined the distribution of the mRNA
encoding for the growth-associated protein GAP-43 in the brain stem of
adult rats. GAP-43 was expressed at the highest level in the nucleus raphe
dorsalis (NDR), nucleus centralis superior (NCS), substantia nigra compacta
(SNc), ventral tegmental area (VTA), and locus coeruleus (LC). An
intermediate level of signal was detected over the periaque- ductal gray,
superior colliculi, and thalamic region, and no significant signal was
detected in the substantia nigra pars reticulata and red nucleus. The
hybridization signals of GAP-43 mRNA and tryptophan hydroxylase mRNA
completely overlapped in the NDR and NCS, and signals for GAP-43 mRNA and
tyrosine hydroxylase mRNA overlapped in the SNc, VTA, and LC. The
disappearance of the hybridization signal for GAP-43 mRNA after
intracerebroventricular injections of the neurotoxins
5,7-dihydroxytryptamine (5,7-DHT) or 6-hydroxydopamine (6-OHDA) indicated
that high levels of GAP-43 are synthesized in the serotonergic neurons of
the raphe nuclei and in the catecholaminergic neurons of the SNc, VTA, and
LC. In light of the role of GAP-43 in axonal outgrowth, modulation of
signal transduction, and release of different neurotransmitters in the
adult CNS, this phosphoprotein might be involved in the functional
plasticity and synaptic transmission of monoaminergic neurons.