FIGURE 4.

4‐AA increases [Ca²⁺]_i through activation of TRPV1 channels in cultured primary sensory neurons following pretreatment of the cells with PGE₂. (a) 4‐AA (50, 25, 10, and 1 μM) increases [Ca²⁺]_i in primary sensory neurons, sensitised by PGE₂ in a concentration‐dependent manner. (b) The proportion of 4‐AA‐responding cells is also increased following PGE₂ pretreatment. *P< .05, significant effect of 4‐AA. (c–f) Representative recordings of changes in the [Ca²⁺]_i by various conditions. Following PGE₂ pretreatment, 4‐AA (50 μM) induces an increase in the [Ca²⁺]_i in the presence of PGE₂ (c). While the 4‐AA‐induced increases in the [Ca²⁺]_i were not affected by the TRPA1 channel antagonist HC‐030031 (10 μM) in the presence of PGE₂ (1 μM), at the start of washing PGE₂, HC‐030031 and 4‐AA out from the recording chamber, a “buffer‐evoked” calcium transient emerged (d). Importantly, no such “buffer‐evoked” calcium transient was observed when 4‐AA was missing from the superfusate (e). The TRPV1 channel antagonist capsazepine (CAPZ; 10 μM), but not the TRPA1 channel antagonist, blocked the 4‐AA‐evoked calcium transient in the presence of PGE₂ (f). (g) Average normalised amplitudes of responses of cultured primary sensory neurons in various conditions. Data shown are means SEM from a number of neurons, as follows: 4‐AA, n = 156; PGE₂ +4‐AA, n = 156; PGE₂+4‐AA+CAPZ, n = 142; PGE₂+4‐AA+HC, n = 100; PGE₂ +CAPZ, n = 115; PGE₂+HC, n = 289: PGE₂, n = 156. * P< .05, significant differences; one‐way ANOVA with Tukey's test