Fig. 6: TRPV1 overexpression in TRPM8+ neurons results in cold allodynia.
From: TRPV1 activity and substance P release are required for corneal cold nociception
a Schematic diagram for the generation of Trpm8CreER/+; ROSA26Trpv1/+ mice. b Representative calcium transients of TRPM8+ neurons in response to the TRPM8 agonist cryosim-3 (10 µM) and TRPV1 agonist capsaicin (Cap, 1 µM) in Trpm8CreER/+; ROSA26Trpv1/+ mice and control ROSA26Trpv1/+ mice. c Quantification indicates that a significantly increased fraction of TRPM8+ neurons respond to capsaicin in Trpm8CreER/+; ROSA26Trpv1/+ mice (n = 5), compared with control ROSA26Trpv1/+ mice (n = 3). d Representative images showing TRPV1-immunoreactivity (TRPV1-IR, green) in tdTomato-labeled TRPM8+ neurons (Tdt, red) from Trpm8CreER/+; ROSA26Trpv1/tdTomato and control Trpm8CreER/+; ROSA26tdTomato/+ mice. Arrows indicate TRPV1+/TRPM8+ neurons. e Quantification showing upregulated TRPV1-IR in TRPM8+ neurons from Trpm8CreER/+; ROSA26Trpv1/tdTomato mice (n = 3), compared with control Trpm8CreER/+; ROSA26tdTomato/+ mice (n = 3). f TRPM8-agonist cryosim-3 (0.025 nmol in 1 μL) evoked significantly more reflex blinking in Trpm8CreER/+; ROSA26Trpv1/+ mice (n = 7) than in control ROSA26Trpv1/+ mice (n = 6). The vehicle (0.9% NaCl) did not induce significant reflex blinking in either Trpm8CreER/+; ROSA26Trpv1/+ (n = 7) or ROSA26Trpv1/+ mice (n = 6). g Innocuous cold (19 °C) evoked significantly more reflex blinking in Trpm8CreER/+; ROSA26Trpv1/+ mice (n = 7) than in control ROSA26Trpv1/+ mice (n = 6). h Noxious heat (45 °C) elicited similar ocular nociception-associated reflex blinking responses in both Trpm8CreER/+; ROSA26Trpv1/+ (n = 7) and control ROSA26Trpv1/+ mice (n = 6). i Evaporative cooling evoked by acetone applied onto the paw skin elicited more significant nociception-associated flicking and licking responses in Trpm8CreER/+; ROSA26Trpv1/+ mice (n = 6) than in control ROSA26Trpv1/+ mice (n = 6). j Trpm8CreER/+; ROSA26Trpv1/+ (n = 7) and control ROSA26Trpv1/+ mice (n = 6) display similar sensitivity to heat in the Hargreaves test. Data are expressed as mean ± s.e.m. Statistical analysis by two tailed Student’s t-test. n.s. not significant; *P < 0.05; ***P < 0.001. All images shown are representative of three independent experiments using tissues from at least three different mice. Scale bar: 100 μm. Source data are provided as a Source Data file.
