Figure 5.

Effects of SP require simultaneous activation of NK₁ and NK₂ receptors. Pretreatment with either the NK₁ antagonist, GR-82334 (10⁻⁷ M; (a), or the NK₂ antagonist, MEN 10,627 (10⁻⁷ M; b), abolished the effects of SP on Ca²⁺ transients (open bars) and basal Ca²⁺ (closed bars) in relation to control. Application of NK₁ agonist SSP (10⁻⁷ M) did not significantly affect spontaneous Ca²⁺ transients or basal Ca²⁺ level (c). Application of NK₂ agonist, NKA (10⁻⁷ M) in the continued presence of SSP reduced Ca²⁺ puffs and increased basal Ca²⁺. Thus, combination of these agonists mimicked the effects of SP. (d) Effects when the order of application of NK₁ and NK₂ agonists was reversed. (e) Effects of SSP and NKA on inward currents. The I/V curves show that there was little or no effect on voltage-dependent inward currents after application of NKA (10⁻⁷ M), but the current was greatly enhanced by subsequent addition of SSP (10⁻⁷ M) in the continued presence of NKA. Thus, combination of NK₁ and NK₂ agonists mimicked the effects of SP on inward current.