2.4. Nere recording
The following procedure was identical for anesthetized
and decerebrate preparations. The
glossopharyngeal nerve was cleared of connective
tissue and sectioned very close to where it enters
the first gill arch but before it splits into pre- and
post-trematic branches. The opening in the skull
was filled with paraffin oil to insulate and protect
the nerve from desiccation. The vagal branch to
the first gill arch was left intact. The perineurim
was carefully peeled from the nerve and small
bundles of fibers were picked from the main
branch and placed over the electrodes. When activity
synchronous with ventilation was detected,
the nerve was spilt until single unit or paucifiber
activity could be recorded. Nerve activity was
recorded using a Grass amplifier (P5 Series) with
associated power supply (RPS 107), high
impedance head stage (model HIP5 Hi Z probe)
and a platinum/iridium bipolar electrode. Nerve
activity and ventilatory movements were stored
and analyzed using a computer data acquisition
system (Windaq).
Ventilation and nerve activity were recorded for
a 10–20 min control period. Gallamine (0.2 ml,
20 mg/ml, Davis and Geck) was given i.p. and
data were recorded until ventilation ceased and
for 10 min thereafter. Assisted ventilation was
maintained constant throughout all experiments,
in both anesthetized and decerebrate preparations,
before and after paralysis. Ventilation did
not change after paralysis, indicating that blood
gases were maintained by the assisted ventilatory
water flow.