Different Time Courses of Mono- and Bi-Liganded Bursts of Channel Openings of Adult nAChR Molecules Formed by the Reactions of Transmembrane Regions.

We recorded transmembrane currents through single nicotinic acetylcholine receptors (nAChRs) in cell-attached patches at high temporal resolutions from cultured and transiently transfected HEK 293 cells. Receptor activation was elicited by acetylcholine (ACh) or epibatidine (Ebd) at concentrations ranging from 0.01 to 100 µM, binding to one (R or R) or both extracellular ligand binding sites (R).

α-Conotoxin M1 (CTx) blocks αδ binding sites of adult nicotinic receptors while ACh binding at αε sites elicits only small and short quantal synaptic currents.

In 'embryonic' nicotinic receptors, low CTx concentrations are known to block only the αδ binding site, whereas binding of ACh at the αγ-site elicits short single channel openings and short bursts. In adult muscles the αγ- is replaced by the αε-site. Quantal EPSCs (qEPSCs) were elicited in adult muscles by depolarization pulses and recorded through a perfused macropatch electrode.

Agonists binding nicotinic receptors elicit specific channel-opening patterns at αγ and αδ sites.

'Embryonic' muscle-type nicotinic acetylcholine receptor channels (nAChRs) bind ligands at interfaces of α- and γ- or δ-subunits. αγ and αδ sites differ in affinity, but their contributions to opening the channel have remained elusive. We compared high-resolution patch clamp currents evoked by epibatidine (Ebd), carbamylcholine (CCh) and acetylcholine (ACh).

Depolarization amplitude and Ca2+ -inflow control the time course of quantal releases at murine motor nerve terminals.

In order to test whether the time courses of quantal releases after a depolarization pulse are affected by the depolarization amplitude, time courses were measured for small depolarization pulses that elicited close to threshold releases and for large depolarizations that elicited releases approaching saturation level. Diaphragms of young mice were excised and superfused with Bretag's solution at 18 degrees C. Synaptic currents were elicited and recorded through a perfused macropatch pipette.

Glutamatergic autoinhibition of quantal release augments the early phase of releases after a depolarization pulse.

At the crayfish neuromuscular junction, glutamatergic autoinhibition of quantal excitatory postsynaptic current (qEPSC) release is mediated by a presynaptic DL-glutamate transporter and its associated Cl- conductance. I investigated whether it also affects the time course of release. qEPSCs were recorded with a perfused macroelectrode through which depolarization pulses and D- or L-glutamate could be applied to a terminal.

Short openings in high resolution single channel recordings of mouse nicotinic receptors.

The temporal fine structure of single channel currents was studied to obtain information on how agonists open nicotinic acetylcholine receptor channels. Currents were recorded from mouse myoballs with quartz pipettes in the on-cell mode of the patch-clamp technique. With 62 kHz filter cut-off and root mean square (r.

Both d- and l-glutamate induce transporter-mediated presynaptic autoinhibition of transmitter release.

In crayfish motor nerve terminals l-glutamate (Glu) is the excitatory transmitter and low l-Glu concentrations exert autoinhibition by inhibiting release of Glu quanta from the terminals. This autoinhibition has been shown to be mediated by binding and transport of l-Glu by Glu transporters in the presynaptic membrane. Activated transporters open an associated Cl(-) channel and inhibit release [J.

A receptor for presynaptic glutamatergic autoinhibition is a glutamate transporter.

Monoquantal excitatory postsynaptic currents were recorded by means of a perfused macropatch electrode from 9 to 15 micro m stretches of crayfish neuromuscular junctions. The excitatory transmitter l-glutamate superfused to a terminal inhibits quantal release by activating autoreceptors [Parnas et al. (1996) Eur.

Quantal endplate currents from newborn to adult mice and the switch from embryonic to adult channel type.

Quantal endplate currents (qEPCs) were recorded extracellularly by a macropatch electrode from excised diaphragms of mice. During the first 3 days after birth, the mean rise time t(r) was 0.5 ms (0.