Slow voltage-dependent changes in channel open-state probability underlie hysteresis of NMDA responses in Mg(2+)-free solutions.

Many single-channel studies rely on the assumption that the channels are functioning under steady-state conditions. In examining the basis for nonlinear whole-cell current-voltage curves in Mg(2+)-free solutions we discovered that N-methyl-D-aspartate (NMDA) channels in excised patches reversibly shifted their open-state probability (Po) in a voltage-dependent way, exhibiting approximately 3- to 4-fold greater Po at positive potentials than at rest. Changes in Po were mainly attributable to shifts in frequency of channel opening.

Antibodies to the alpha q subfamily of guanine nucleotide-binding regulatory protein alpha subunits attenuate activation of phosphatidylinositol 4,5-bisphosphate hydrolysis by hormones.

The subfamily of guanine nucleotide-binding regulatory (G proteins) designated Gq has been shown to regulate the activity of phospholipase C by reconstitution. However, the role of these proteins in hormonal regulation of this activity has not been demonstrated. Two antisera were used in attempts to interrupt this pathway.

Galanin inhibits a dihydropyridine-sensitive Ca2+ current in the RINm5f cell line.

Mechanisms of action of the neuropeptide galanin, a putative neuromodulator in the central and peripheral nervous systems, have been evaluated extensively in insulin-secreting cells isolated from pancreas and cell lines derived from pancreatic tumors. Galanin inhibits insulin secretion from these cells through several mechanisms, including activation of ATP-dependent K+ channels and inhibition of adenylyl cyclase leading to a decrease in cAMP. Here we report that galanin also inhibits a dihydropyridine-sensitive Ca2+ current.

Multiple effects of tetraethylammonium on N-methyl-D-aspartate receptor-channels in mouse brain neurons in cell culture.

1. The mechanisms of tetraethylammonium (TEA) antagonism of N-methyl-D-aspartate (NMDA) responses were investigated in cultured mouse cortical neurons by analysing single-channel and whole-cell currents from patch clamp recordings. TEA (1-5 mM) decreased whole-cell NMDA responses.

Pharyngeal/upper esophageal sphincter pressure dynamics in humans. Effects of pharmacologic agents and thermal stimulation.

Extensive physiological studies of swallowing have been carried out in laboratory animals; however, similar studies in humans have been limited by available technology. In this study we describe the use of a solid-state circumferential sphincter transducer to define manometric characteristics of the human pharynx and upper esophageal sphincter (UES). Effects of pharmacologic agents and thermal stimulation are also described.

Mechanisms of blockade of excitatory amino acid receptor channels.

Ion channels coupled to NMDA, kainate and AMPA receptors are the target of pharmacological regulation by a variety of drugs and ions. While these channels are all nonselectively permeated by Na+ and K+ ions, the NMDA receptor-channel complex contains a number of pharmacological sites distinct from those found on the others. For example, Mg2+ ions rapidly and reversibly block open NMDA channels in a highly voltage-dependent manner.

CTP-dependent lipid kinases of yeast.

Membrane fractions from yeast Saccharomyces cerevisiae catalyzed a transfer of gamma-phosphate from [gamma-32P]CTP into membranous lipids. Phosphorylated compounds were identified as phosphatidic acid and dolichyl phosphate (DolP). The membrane fraction also catalyzed phosphorylation of the exogenous dolichol.

The role of divalent cations in the N-methyl-D-aspartate responses of mouse central neurones in culture.

1. Single-channel currents activated by N-methyl-D-aspartate (NMDA) agonists were analysed in the presence of various extracellular concentrations of divalent cations in outside-out patches from mouse neurones in primary culture. 2.

Quisqualate- and kainate-activated channels in mouse central neurones in culture.

1. Quisqualate- and kainate-induced currents were recorded in mouse central neurones in culture, using both 'whole-cell' and 'outside-out' configurations. Experiments were made at room temperature.

N-methyl-D-aspartate-activated channels of mouse central neurones in magnesium-free solutions.

1. The whole-cell and outside-out configurations of the patch-clamp method were used to investigate the properties of the channels activated by N-methyl-D-aspartate (NMDA channels) in mouse central neurones in culture. Recording was made in Mg2+-free solutions.

Ionic channels in mouse astrocytes in culture.

We observed Na, K, and Cl voltage-dependent currents in a patch-clamp study of mouse brain astrocytes. In whole-cell recordings, depolarizations activated inward currents that were identified as Na currents since they were blocked by TTX, although complete block required high concentrations (greater than 1 microM). The corresponding single-channel Na currents were observed in outside-out patches.

Magnesium gates glutamate-activated channels in mouse central neurones.

The responses of vertebrate neurones to glutamate involve at least three receptor types. One of these, the NMDA receptor (so called because of its specific activation by N-methyl-D-aspartate), induces responses presenting a peculiar voltage sensitivity. Above resting potential, the current induced by a given dose of glutamate (or NMDA) increases when the cell is depolarized.

Ionic mechanism of muscarinic cholinergic depolarization of mouse spinal cord neurons in cell culture.

1. Muscarinic cholinergic actions were investigated in a population of large multipolar spinal cord neurons in primary dissociated cell culture using conventional intracellular recording and single-microelectrode voltage-clamp techniques. 2.

Muscarine-sensitive voltage-dependent potassium current in cultured murine spinal cord neurons.

Muscarine produced membrane depolarization and decreased membrane conductance of mouse spinal cord neurons in dissociated cell culture. When the neurons were voltage clamped, muscarine evoked inward currents which increased with membrane depolarization and decreased with membrane hyperpolarization. However, the muscarine-induced inward currents did not invert at large negative potentials, suggesting that muscarine decreased a voltage-dependent potassium current (m-current) [2].

Flicker fusion characteristics of rod photoreceptors in the toad.

Critical fusion frequency (CFF) of toad rods was examined at various intensities using intracellular recordings. Data were compared to CFF measurements (as a function of intensity) obtained with the electroretinogram (ERG) and with a horizontal cell. In all instances the rod (and rod mediated) responses produced a curve which increased monotonically to a high frequency asymptote at about 6 Hz.

Substance P: ionic basis for depolarizing responses of mouse spinal cord neurons in cell culture.

Intracellular recording methods were used to investigate the ionic basis for the postsynaptic actions of substance P (SP) on mouse spinal cord neurons grown in primary dissociated cell culture. SP and an analog, eledoisin-related peptide (ERP), were applied to single neurons by pressure ejection of peptide-containing solutions from blunt (2- to 10-micrometers) glass micropipettes. SP and ERP had similar excitatory actions, increasing spontaneous activity and depolarizing neurons by decreasing membrane conductance.

GABA and bicuculline actions on mouse spinal cord and cortical neurons in cell culture.

The neutral amino acid gamma-aminobutyric acid (GABA) produced membrane hyperpolarization and increased membrane chloride ion conductance of spinal cord (SC) and cortical (CTX) neurons in cell culture. GABA dose-response curves were obtained for SC neurons by pressure applying known concentrations of GABA from micropipettes with large tips (miniperfusion pipettes). GABA response threshold was about 2 micrometers and large responses were elicited at GABA concentrations greater than 10 micrometers.

Membrane depolarization and prolongation of calcium-dependent action potentials of mouse neurons in cell culture by two convulsants: bicuculline and penicillin.

The convulsant compounds bicuculline (BICUC) and penicillin (PCN) are antagonists of GABA-mediated synaptic inhibition. In addition, we have shown that BICUC and PCN produced membrane depolarization of mouse spinal cord neurons in primary dissociated cell culture by blocking a potassium conductance, a non-synaptic direct effect. Both compounds also prolonged calcium-dependent action potentials of mouse dorsal root ganglion and spinal cord neurons in cell culture.

Bicuculline: a convulsant with synaptic and nonsynaptic actions.

The convulsant bicuculline (BICUC) had both synaptic and nonsynaptic actions on mouse spinal cord neurons in primary dissociated cell culture. BICUC antagonized postsynaptic responses to the inhibitory neurotransmitter GABA (a synaptic action) and produced direct membrane depolarization by blocking a membrane potassium conductance and directly prolonging calcium-dependent action potentials (nonsynaptic actions). In cultured spinal cord neurons, BICUC also produced paroxysmal depolarizing events (PDE), which might be equivalent to in vivo convulsant-induced bursting in spinal cord neurons or paroxysmal depolarizing shifts (PDS) in cortical neurons.

Substance P decreases a potassium conductance of spinal cord neurons in cell culture.

Substance P (SP) produced membrane depolarization and decreased membrane conductance of mouse spinal cord neurons in primary dissociated cell culture. SP-responses were abolished by intracellular tetraethylammonium suggesting that SP decreased potassium conductance. Reversal of SP-responses was not observed with membrane hyperpolarization suggesting that SP reduced a voltage-dependent potassium conductance that was activated by membrane depolarization.

Substance P and somatostatin actions on spinal cord neurons in primary dissociated cell culture.

In this paper, we have demonstrated that two peptides, SP and SRIF, which have been localized to and are released from small DRG neurons, have specific but different actions on mouse spinal cord neurons in PDC culture. SP has been shown to be excitatory by decreasing potassium conductance and to a lesser extent sodium conductance; SP also appeared to evoke release of neurotransmitter. SRIF has been shown to modify neurotransmitter release by a presynaptic action.

A single-stranded nucleic acid-binding protein from Artemia salina. II. Interaction with nucleic acids.

A helix-destabilizing protein, HD40 (Mr 40,000), isolated from the cytoplasm of Artemia salina (Marvil, D.K., Nowak, L.

A single-stranded nucleic acid-binding protein from Artemia salina. I. Purification and characterization.

A protein that binds tightly to single-stranded but not to double-strained nucleic acids has been purified to homogeneity from a high salt wash of ribosomes from cryptobiotic Artemia saline gastrulae. The protein, designated HD40 to indicate a helix-destabilizing protein with a molecular weight of 40,000, is present in the high-salt ribosomal wash at a level of about 2 molecules per 80 S ribosome. The protein is monomeric at salt concentrations from 0.