Pharmacological analysis of Ca²⁺ influx in vagal neurons in response to divalent cation removal/re-introduction.

<p>Mean ± S.E.M. Ca²⁺ responses of vagal neurons as measured by Fura 2AM. Blocked line denotes the chelation of divalent cations, at all other times Ca²⁺ and Mg²⁺ are at 2.2 mM and 1.2 mM, respectively. All neurons responded to KCl (75 mM). A, the response to divalent chelation (5 mM EDTA, 0 Ca²⁺, 0 Mg²⁺) or Ca²⁺ chelation (5 mM EGTA, 0 Ca²⁺) in combination with various Mg²⁺ concentrations (0, 0.2 and 1.2 mM). B, the effect of SOC blocker SKF96365 (10 µM; grey squares) or TRPM7 blocker spermine (20 µM; black outlined boxes) on the response to EDTA (5 mM; 0 Ca²⁺, 0 Mg²⁺). C, the effect of a combination of clinidipine and nifedipine (both 10 µM; grey squares) or a combination of ruthenium red (RR, 30 µM) and nifedipine (10 µM; black outlined boxes) on the response to EDTA (5 mM; 0 Ca²⁺, 0 Mg²⁺). D, the effect of total external Na⁺ replacement with NMDG⁺ (grey squares) on the response to EDTA (5 mM; 0 Ca²⁺, 0 Mg²⁺). E and F, the response to the absence of Mg²⁺ combined with various Ca²⁺ concentrations titrated with 5 mM EGTA (resulting in 0 nM (n = 94), 10 nM (n = 56), 100 nM (n = 32), 1 µM, (n = 63), 10 µM, (n = 47), 100 µM, (n = 58), 2.2 mM (n = 21)). E, Mean ± S.E.M. Ca²⁺ responses against time demonstrating the ‘immediate’ Ca²⁺ response observed <i>during</i> treatment with low divalent cations and the ‘addback’ response observed following re-introduction of divalent cations (Ca²⁺ 2.2 mM, Mg²⁺ 1.2 mM). F, maximal response observed during ‘immediate’ response (grey squares) and during ‘addback’ response (black squares).