The aim of the present study was to examine
the distribution of cells expressing connexin 26 (Cx26)
in the suboesophageal visceral, left and right parietal and
left and right pleural ganglia of the snail Helix aspersa
by immunocytochemistry. Altogether we have found
approximately 452 immunoreactive neurons which
represent the 4.7% of the total neurons counted. The
stained large neurons (measured diameter 55-140 μm)
occurred mostly on the peripheral surface of the ganglia
while the small immunostained cells (5-25 μm diameter)
were observed in groups near the neuropil. The number
of large neurons giving positive Cx26-like
immunostaining was small in comparison with that for
medium (30-50 μm diameter) and small sized cells. The
expression of Cx26 was also observed in the processes
of glia cells localized among neurons somata and in the
neuropil showing that the antiserum recognized epitopes
in both protoplasmic and fibrous glia cells of Helix
aspersa. The neuropils of all ganglia showed fibers
densely immunostained. While we have observed a good
specificity for Cx26-antiserum in neurons, a lack of
reaction for Cx43 antiserum was observed in neurons
and glia cells. The reaction for enolase antiserum in
neurons was light and non-specific and a lack of reaction
in glia cells and processes for GFAP antiserum was
observed. Although the percentage of positive neurons
for Cx26 antiserum was low is suggested that in normal
physiological conditions or under stimulation the results can be considered of interest in the interpretation
of Helix aspersa elemental two neuron networks synchronizing activity, observed under applied
extremely low frequency magnetic fields