Methods: Under anaesthesia (alphaxalone/alphadalone, induction: 6mg/kg, maintenance: 6-8mg/kg/hr, iv) five female ferrets were prepared to enable intermittent recording of the JOR evoked by electrical tooth-pulp stimulation (J Neurosci Methods, 38: 35-40; 1991). The upper and lower left canine teeth were stimulated independently using graded intensity constant current stimuli. Three recordings of the JOR were made under anaesthesia at one week intervals prior to a chronic constriction injury to the ipsilateral lingual nerve using four loose chromic gut ligatures. Six subsequent recordings were made weekly, starting one day after the nerve injury. JOR thresholds were recorded and stimulus-response curves determined for JOR amplitude and integral. Comparisons were made between pre- and post-injury responses.
Results: The lingual nerve injury did not result in any significant changes in JOR threshold, amplitude or integral (ANOVA, p>0.3).
Conclusion: Injury to the lingual nerve does not appear to change the excitability of the neurones in the inferior alveolar nerve that are involved in the jaw-opening reflex. Thus, in the trigeminal system, we have not found evidence of a role for adjacent undamaged nerve fibres in the development of nerve injury-induced pain.