Sensitivity of peripheral nerve fibres to sodium pentobarbital anaesthesiain rat

The sensitivity of different classes of peripheral nerve fibres to anaesthe sia with sodium pentobarbital in rat was tested. The basic approach was to examine changes in compound action potential (Chf) in a rat sural nerve ind uced by sodium pentobarbital. Rats were either sacrificed by cervical dislo cation (control) or anaesthetized with sodium pentobarbital (100 mg/kg, i.p .), and a 30 mm long sural nerve segment excised and placed on electrodes i n thermostatically controlled recording chamber. CAPs were evoked by electr ically stimulating the sural nerve segment with supra-threshold stimuli. CA P in control sural nerves consisted of the early component (A axons: 32.73 +/- 2.91 m/s) and the late component (C axone: 0.92 +/-; 0.05 m/s) with pea k voltage amplitudes 4.9 +/- 1.0 mV and 0.1 +/- 0.03 mV, respectively. Anae sthesia with sodium pentobarbital had no effect on CAP latency. However, th e amplitude of CAP of both A and C axone was reduced by approximately 40% a nd 50%, respectively. The depressant effect of pentobarbital on CAPs was st atistically significant for both groups of axons (p<0.01). Non-selective se nsitivity of A and C axons to pentobarbital suggests even distribution of r eceptors for GABA in these two populations of axons in the rat peripheral n erve.