Figure 6.

PMA incubation of corneal TRPM8(+) nerve endings reduced their ongoing activity and cold-evoked responses. (A) Experimental arrangement of the ex vivo preparation used to record nerve terminal impulse (NTI) activity from corneal cold-sensitive nerve endings in isolated mouse eyes (modified from [5]). (B) Examples of 2.5 s of NTI activity recording from a TRPM8(+) cold-sensitive nerve ending in basal conditions, in response to cold, and after rewarming. (C–E) Ongoing NTI activity before and after application of control solution (C), 2 μM PMA (D) or 2 µM 4α-PMA (E) in cold-sensitive nerve endings. Statistical significance was assessed by paired t test; * p < 0.05; n.s., not significant. (F) Frequency change of NTI activity evoked by consecutive cold pulses from 34 to 20 °C, at time 0 and 40 min, after application of control solution, PMA or 4α-PMA. Data is expressed as the difference between the peak of cold-evoked response at 40 min minus the peak of the response obtained during the first cold pulse in each single nerve ending. Statistical significance was assessed by an ANOVA test in combination with a Dunnett’s post hoc test; * p < 0.05; control, n = 6; PMA, n = 7; 4α-PMA, n = 5; n.s. not significant.