A new conus peptide ligand for mammalian presynaptic Ca2+ channels

Down‐regulation of non‐L‐, non‐N‐type (Q‐like) Ca2+ channels by Lambert‐Eaton myasthenic syndrome (LEMS) antibodies in rat insulinoma RINm5F cells

“…Thus, the pharmacological profile of the non-L, non-N-type channel controlling neurotransmitter release in mammalian motoneurons is close, although not identical, to the P-type channel of central neurons [lo]. The P-type channel of cerebellar Purkinje neurons is irreversibly blocked by nanomolar concentrations of o-Aga-IVA and micromolar amounts of o-CTx-MVIIC [20]. In this respect, the non-N, non-L-type channel of RINmSF cells resembles more the P-type channel of motoneuron terminals than that of central neurons: it is reversibly blocked by nanomolar concentrations of o-Aga-IVA and irreversibly abolished by micromolar concentrations of o-CTx-MVIIC [15].…”

Presynaptic plasticity: The regulation of Ca2+-dependent transmitter release

“…Blockade of all four classes of channels has been found to inhibit exocytosis. In fact, the original classification may not hold for the Ca 2+ channels coupled to exocytosis and recent evidence suggests that presynaptic N-and P-type channels may in fact represent an overlapping superfamily of channels with overlapping pharmacological profiles with respect to the sensitivity for different fractions of aga/FTX-and og-conotoxins (see Mintz et al, 1991;Hillyard et al, 1992;Pocock and Nicholls, 1992). In order to be able to measure transmitter release, stimuli are often chosen which are rather different from those encountered under physiological conditions, for instance a persistent depolarization by [K +]e-elevations.…”

A single non-L-, non-N-type Ca2+ channel in rat insulin-secreting RINm5F cells

“…The single non-L-, non-N-type channel: Q-like versus P-type Of the three non-L-, non-N-type channels described in central neurons (Q, P and R; [12,21,26]) the one observed in RINm5F cells seems more closely related to the Q-type. The R-type channel described in rat cerebellar granules has kinetic properties sharply different from those illustrated here.…”

“…When acutely applied to the cell, -CTx-GVIA was delivered through a separate glass pipette kept out of the bath and moved close to the cell immediately before toxin application. Due to the slow washing out of the toxin in 100 mM Ba 2+ solutions [12,31], the dish was changed after each cell recording.…”

“…There was no way to block either one of the two channels by acutely applying selective toxins outside the recording pipette. The possibility of isolating N-type from P-or Q-like channels by chronic treatment with 10 µM -CTx-MVIIC (30 min, [12]) was biased by the partial leaky conditions of the cells after toxin treatment. For these reasons the separation of the two non-L-type channels was postponed to more suitable patch configurations (see below) and the attention focused on the properties of non-L, non-N-type channels in cell-attached patches of RINm5F cells chronically treated with -CTx-GVIA.…”