Figure 2.

PACAP-induced increase in excitability is temperature-sensitive. A: Recordings from different cells showed that 20 nM PACAP increased excitability when the bath solution was 33°C (A₁), but not when the bath temperature was 22°C (A₂). The recording in A₃ demonstrated that the addition of 1 mM BaCl₂ (Ba²⁺) increased excitability at 22°C. In all three recordings, the cells exhibited a phasic firing pattern prior to the addition of PACAP (A₁, ₂) or barium (A₃). The firing pattern shifted to multiple firing in A₁ and A₃, but not in A₂. The amplitude of the 1 sec depolarizing current pulse was 0.3 nA in each experiment. B: The percentage of cells exhibiting multiple firing in 20 nM PACAP was significantly greater when the temperature was 32 – 34°C (n = 13 cells) than when the bath temperature was 21 – 25°C (n = 23 cells; Fisher’s exact test, Ρ < 0.0001; Also, at 32 – 34°C: control (n = 28) vs. PACAP (n = 13), significantly different, Ρ < 0.0001; at 21 – 25°C: control (n = 10) vs PACAP (n = 23), not significantly different, Ρ = 0.5363). C: Averaged excitability curves generated in the cells maintained at either 33 – 34°C or 21 – 25°C prior to and during exposure to 20 nM PACAP. The number of action potentials generated at each current step was significantly greater (P< 0.003, indicated by asterisks) at the warmer temperature in the presence of PACAP (n = 13) when compared to untreated control at warm temperature (n = 28), and to PACAP at room temperature (n = 23). The number of action potentials generated at each current step was not different between untreated control (n=10) and PACAP at room temperature. Reprinted with permission from the Journal of Neuroscience (Merriam et al, 2013).