The effect of tachykinin receptor agonists on paired pulse depression. All agonists were perfused for 10 min. (a) Bars represents the control paired pulse depression using an interstimulus interval of 20 ms (PS2 amplitude expressed as a % of PS1, open bars), compared to that recorded in the presence of each agonist (filled bars). Substance P methyl ester significantly increased the amplitude of PS2, p > 0.05, n = 9. (β8Ala) neurokinin A (4–10) and senktide failed to have any significant effect on the amplitude of PS2, n = 4 for both. Substance P significantly increased the amplitude of PS2, p > 0.05, n = 7. (b) Example synaptic response recorded from 3 different representative slices. Top row of traces are controls, bottom traces are those recorded during perfusion of each tachykinin agonist. Scale bar represents 1 mV and 10 ms.