Figure 6.
Representative audible and ultrasonic vocalizations from phenotyped male rats in the SNL model of neuropathic pain. Original real-time waveform and spectrogram recordings of vocalizations evoked in response to brief (10 s) noxious (1500 g/6 mm2) mechanical stimulation of the affected hindpaw 4 weeks after induction of sham (A,B) or SNL (C,D) surgery in phenotyped male rats. For details, see Section 2.5.3. Mechanical stimuli were applied to the hindpaw in each recording period, as indicated by the highlighted yellow section of the waveform (upper panel, red arrow indicates initiation of noxious stimulus application); the total duration of the recording is 1 min. Boxes (events) in the spectrogram (lower panel) represent the presence of audible (blue; 20 Hz–16 kHz) and ultrasonic (red; 25 ± 4 kHz) vocalizations during the 10 s application of mechanical stimuli. Male FE− sham rats (A) showed more vocalization events in response to noxious stimulus than male FE+ sham rats (B). Male FE− SNL rats (C) showed more vocalization events in response to noxious stimulus than male FE+ SNL rats (D). FE: fear extinction; SNL: spinal nerve ligation; USV: ultrasonic vocalizations.