Mf. Klemm et al., DISTRIBUTION OF SYNAPTIC BOUTONS AROUND IDENTIFIED NEURONS LYING IN THE CARDIAC PLEXUS OF THE GUINEA-PIG, Journal of the autonomic nervous system, 66(3), 1997, pp. 201-207
Neurones in the cardiac plexus of the guinea-pig were subdivided into
three groups according to their electrophysiological properties and su
bsequently labelled with neurobiotin. Preparations were counterstained
with antibodies to synaptophysin to reveal boutons containing synapti
c vesicles. Two of the three groups of cells which, in the electrophys
iological studies were found to receive excitatory synaptic inputs wer
e associated with numerous synaptophysin positive boutons. Cells of th
e other group, which did not appear to receive any synaptic inputs wer
e associated with fewer synaptophysin positive boutons. Wholemount pre
parations were double stained with antibodies to Protein Gene Product
9.5 and synaptophysin. This revealed most neurones, along with vesicle
filled boutons. Ganglia generally contained less than 10 neurones wit
h a range between one and over 30. In wholemount preparations it was f
ound that about 90% of the cells were associated with a large number o
f synaptophysin positive boutons whilst the remaining cells were assoc
iated with very few synaptophysin positive boutons. These results are
consistent with the idea that a proportion of cardiac ganglion cells f
ail to receive a synaptic input and suggest that by staining wholemoun
t preparations of guinea-pig cardiac plexus with antibodies to synapto
physin it is possible to differentiate between groups of cells which r
eceive a synaptic input and those which fail to receive a synaptic inp
ut. Approximately 10% of intrinsic cardiac neurones appear to lack a s
ynaptic input. (C) 1997 Elsevier Science B.V.