The alpha and beta subunits of the gamma-aminobutyric acidA (GABAA) receptor were expressed individually in Xenopus oocytes by injection RNA synthesized from their cloned DNAs. GABA-sensitive chloride channels detected several days after with any one three different RNAs (alpha 1, 2, 3) or RNA. induced each alpha-subunit indistinguishable, they had multiple conductance levels (10, 19, 28, 42 picosiemens), activity was potentiated pentobarbital inhibited picrotoxin. usually poorly but showed...

1. End‐plate currents produced by nerve‐released acetylcholine and iontophoretically applied carbachol have been recorded from voltage‐clamped frog cutaneous pectoris neuromuscular junctions made visible with Nomarski differential interference contrast optics. 2. The effectiveness of agonists ‐ that is, the end‐plate conductance change a given dose‐has determined as function post‐junctional membrane potential. 3. As potential is more negative, becomes less effective whereas...

Previous studies have shown that mudpuppy taste receptor cells respond to sour stimuli (weak acids) with depolarizing potentials or action are blocked by the K+ channel blocker tetraethylammonium. Voltage-clamp recordings from isolated indicated exhibit a variety of voltage-dependent conductances and acids reduce current. Since restricted apical surface intact tongue, only 1-2% cell is exposed chemical stimuli. Thus, modification conductance would be an effective transduction mechanism in if...

1. Frog neuromuscular junctions were viewed with Nomarski optics and voltage clamped. Agonist was applied ionophoretically agonist concentrations measured using a micro‐electrode sensitive to quaternary amines. 2. The dose‐response relationship studied the agonists carbamylcholine, suberyldicholine hydroxyphenyl‐propyltrimethylammonium. 3. With all of these agonists, it appeared that ACh receptor could be active when either one or two binding sites occupied. much more likely both...

A PCR-based strategy for amplifying putative receptors involved in murine olfaction was employed to isolate a member (OR3) of the seven-transmembrane-domain receptor superfamily. During development, first cells that express OR3 appear adjacent wall telencephalic vesicle at embryonic day 10. The is uniquely expressed subset olfactory have characteristic bilateral symmetry adult epithelium. This and its specific pattern expression may serve functional role odor coding or, alternatively, play...

The terminal nerve is an anterior cranial that innervates the lamina propria of chemosensory epithelia nasal cavity. function ambiguous, but it has been suggested to serve a neuromodulatory role. We tested this hypothesis by exposing olfactory receptor neurons from mudpuppies (Necturus maculosus) peptide, gonadotropin releasing hormone (GnRH), found in cells and fibers nerve. used voltage-clamped whole-cell recordings examine effects 0. 5-50 micrometer GnRH on voltage-activated currents...

Previous studies have shown that the number of functional acetylcholine receptors (AcChoRs) on chicken ciliary ganglion neurons in culture is considerably smaller than total AcChoRs detected by labeled receptor probes. Here we use patch-clamp recording to show a cAMP-dependent process enhances AcCho response mechanism likely involve an increase AcChoRs. The occurs without requiring protein synthesis and involving detectable cell surface measured with probe. results imply nonfunctional pools...

Olfactory receptor neurons isolated from embryonic, neonatal, and adult mice were studied using the patch-clamp technique. Several distinct types of ion channels characterized in patches membrane neuronal soma dendritic knob neurons, including a 130-pS Ca++-activated K+ channel with voltage-dependent kinetics, an 80-pS voltage-insensitive 25-pS properties similar to inward rectifiers, 40-pS that was activated then inactivated by rapid depolarization. Evidence large-conductance (greater than...

In the pancreatic acinar cell, hormonal stimulation causes a rise in intracellular free Ca2+ concentration by activating inositol 1,4,5-trisphosphate-mediated release of from stores (Berridge, M. J., and Irvine, R. F. (1989) Nature 341, 197-205). The released is, for most part, extruded necessitating mechanism entry reloading (Putney, J. W., Jr. (1990) Cell Calcium 11, 611-624; Rink, T. FEBS Lett. 268, 381-385). However, neither depletion-activated nor signal that activates it is known. We...

Excitatory postsynaptic currents (EPSCs) have been studied in voltage-clamped bullfrog sympathetic ganglion B cells. The EPSC was small, rose to a peak within 1-3 ms, and then decayed exponentially over most of its time-course. For 36 cells at --50 mV (21-23 degrees C), size --6.5 +/- 3.5 nA (mean SD), the mean decay time constant tau 5.3 0.9 ms. showed small negative voltage dependence, which appeared independent temperature, range --90 --30 mV; coefficient dependence --0.0039 +/-0.0014...

Olfactory receptor neurons were isolated without enzymes from the mudpuppy, Necturus maculosus, and tested for chemosensitivity. The cells responded to odorants with changes in firing frequency alterations excitability that detected tight-seal patch electrodes using on-cell whole-cell recording conditions. Chemosensitive exhibited two primary response characteristics: excitation inhibition. Both types of observed different stimulated by mixtures amino acids as well single compound L-alanine,...

1. Synaptic responses to acetylcholine were recorded from garter snake (sp. Thamnophis) neuromuscular junctions with the voltage clamp. 2. In following respects identical in twitch and slow fibres: exponential miniature end‐plate current decay, reversal potential (approximately ‐5 mV), permeant ionic species (Na+, K+, Ca2+, but not Cl‐), two component decay presence of procaine, insensitivity tetrodotoxin, alpha‐bungarotoxin leiurus toxin. 3. The differed several important ways: rate was...

Odors affect the excitability of an olfactory neuron by altering membrane conductances at ciliated end a single, long dendrite. One mechanism to increase sensitivity neurons odorants would be for their dendrites support action potentials. We show first time that isolated from mudpuppy Necturus maculosus contain high density voltage-activated Na+ channels and produce Na-dependent potentials in response depolarizing current pulses. Furthermore, all required steps transduction process beginning...

1. Slow muscle synaptic responses were modelled kinetically in an attempt to define the mechanism by which slow fibre acetylcholine‐operated channels differ from those twitch fibres. 2. Three distinguishable states necessary. 3. All applicable three‐state kinetic schemes considered identify simplest description of data. Experimental tets eliminated several models. Two models not tested because they contained excessive number adjustable parameters. 4. The data fitted postulated (i) opened...

Olfactory sensory neurons (OSNs) fire spontaneously as well in response to odor; both forms of firing are physiologically important. We studied voltage-gated Na + channels OSNs assess their role spontaneous activity. Whole cell patch-clamp recordings from demonstrated tetrodotoxin-sensitive and tetrodotoxin-resistant components current. RT-PCR showed mRNAs for five the nine different channel α-subunits olfactory tissue; only one was tetrodotoxin resistant, so-called cardiac subtype V 1.5....

The dependence of acetylcholine receptor mean single-channel conductance on temperature was studied at garter snake twitch-muscle endplates using fluctuation analysis. In normal saline under conditions where most the endplate current carried by Na+, channel increased continuously from near 0 degrees C to approximately 23 with a Q10 1.97 +/- 0.14 (mean SD). When 50% bath Na+ replaced either Li+, Rb+, or Cs+, did not change significantly; however, any greatest in Cs-saline and decreased ion...