Involvement of ryanodine receptors in EPYLRFamide-mediated reduction of acetylcholine-induced inward currents in Helix lucorum identified neurones

Pivovarov, A.S., Chad, J.E. and Walker, R.J. (2000) Involvement of ryanodine receptors in EPYLRFamide-mediated reduction of acetylcholine-induced inward currents in Helix lucorum identified neurones. Regulatory Peptides, 88 (1-3), 83-93. (doi:10.1016/S0167-0115(99)00125-1).

Abstract

The effects of several modulators of ryanodine receptors (RYRs) on the reduction of acetylcholine induced inward current (ACh-current) evoked by EPYLRFamide (5 ?M, bath application), the potent N-terminally modified analogue of the endogenous Helix heptapeptide SEPYLRFamide, were investigated. These modulators were applied intracellularly. Inward currents were recorded from identified Helix lucorum LPa2, LPa3, RPa3, RPa2 neurones in ganglia preparations using the two-electrode voltage clamp technique. ACh was applied ionophoretically. BAPTA (0.1 mM), chelator of intracellular Ca2+ ryanodine (0.1 mM), agonist/antagonist of RYRs and dantrolene (0.1 mM), antagonist of RYRs decrease the effect of EPYLRFamide. Adenosine (1 mM), ?,?-methylene ATP (0.1 mM), the nonhydrolisable ATP analogue and cyclic adenosine diphosphate ribose (0.1 mM) (agonists of RYRs) potentiate the modulatory effect of EPYLRFamide. Ruthenium red ( mM), antagonist of RYRs and caffeine ( mM), agonist of RYRs do not change the modulatory effect of EPYLRFamide. These data suggest that intracellular Ca2+ and RYRs are involved in the modulatory effect of EPYLRFamide on ACh-currents. It was concluded that EPYLRFamide decreases ACh-current through elevation of basal intracellular level of a putative endogenous agonist of RYRs which activates RYR-dependent mobilization of Ca2+ by binding to the adenine nucleotide site of the ryanodine receptor-channel complex and does not bind the site activated by caffeine.

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Contributors

Author: J.E. Chad

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