ACETYLCHOLINE AND HISTAMINE ARE TRANSMITTER CANDIDATES IN IDENTIFIABLE MECHANOSENSITIVE NEURONS OF THE SPIDER CUPIENNIUS-SALEI - AN IMMUNOCYTOCHEMICAL STUDY
R. Fabian et Ea. Seyfarth, ACETYLCHOLINE AND HISTAMINE ARE TRANSMITTER CANDIDATES IN IDENTIFIABLE MECHANOSENSITIVE NEURONS OF THE SPIDER CUPIENNIUS-SALEI - AN IMMUNOCYTOCHEMICAL STUDY, Cell and tissue research, 287(2), 1997, pp. 413-423
Histochemical and indirect immunocytochemical techniques were used to
search for neuroactive substances and transmitter candidates in identi
fied sensory neurons of two types of cuticular mechanoreceptors in the
spider Cupiennius salei Keys.: (1) in lyriform slit-sense organ VS-3
(comprising 7-8 cuticular slits each innervated by 2 bipolar neurons),
and (2) in tactile hairs (each supplied by 3 bipolar sensory cells).
All neurons are mechanosensitive. A polyclonal antibody against cholin
e acetyltransferase (ChAT) strongly labeled all cell bodies and affere
nt fibers of both mechanoreceptor types. Western blot analysis using t
he same antibody against samples of spider sensory hypodermis and agai
nst samples from the central nervous system demonstrated a clear band
at 65 kDa, corresponding to the molecular mass of ChAT in insects. Mor
eover, staining for acetylcholine esterase (AChE) revealed AChE activi
ty in one neuron of each mechanoreceptor type. Incubation with a polyc
lonal antibody against histamine clearly labeled one neuron in each se
t of sensilla, whereas activity in the remaining one or two cells was
near background. All mechanoreceptor preparations treated with a poly
clonal antiserum against serotonin tested negative, whereas sections t
hrough the central nervous system of the same spiders were clearly lab
eled for serotonin. The presence of ChAT-like immunoreactivity and ACh
E implicates acetylcholine as a transmitter candidate in the two mecha
noreceptive organs. We assume that histamine serves as a mechanosensor
y co-transmitter in the central nervous system and may also act at per
ipheral synapses that exist in these sensilla.