Depiction of Oral Tumor-Induced Trigeminal Afferent Responses Using Single-Fiber Electrophysiology.

Considerable gap in knowledge exists about the mechanisms by which oral tumors regulate peripheral sensory fibers to produce pain and altered sensations. To address this gap, we used a murine model of oral squamous cell carcinoma (OSCC) of the tongue to investigate changes in response properties of trigeminal afferent neurons. Using this model, we developed an ex vivo method for single neuron recordings of the lingual nerve from isolated tongue tissue. Our data demonstrated that the tongue tumor produced increased spontaneous firing of lingual fibers compared to control as well as produced mechanical hypersensitivity and reduced von Frey thresholds of C- and A-slow-high-threshold mechanoreceptors (HTMR) fibers but had no effect on C-LTMR, A-slow-LTMR and A-fast lingual fibers. Mechanically-insensitive fibers were also detected in lingual afferents of the control group, that were significantly decreased in tumor-bearing preparations. Collectively, using single fiber electrophysiology of lingual sensory fibers, we show that human OSCC tumors sensitize peripheral trigeminal nerve terminals, providing a unique opportunity to study mechanisms of oral cancer pain.