Use-dependent block of excitatory amino acid currents in cultured neurons by ketamine

Abstract

1. Mouse hippocampal neurons grown in dissociated cell culture were patch clamped using a whole cell voltage clamp (discontinuous switching clamp) technique. The currents generated by pressure applications of excitatory amino acids were studied over a wide range of holding potentials, and current-voltage curves were plotted. Excitatory amino acids that activated the N-methyl-D-aspartic acid (NMDA) receptor demonstrated some degree of desensitization with repeated applications, whereas the currents observed in response to kainic acid (KAI) did not. Desensitization could be minimized by keeping the frequency of application sufficiently low (i.e., less than 0.1 Hz). 2. The short-acting dissociative anaesthetic, ketamine (2-50 microM), selectively blocked L-aspartic acid (L-Asp), NMDA, and L-glutamic acid (L-Glu) currents while sparing those in response to KAI. Therefore, ketamine is a relatively selective blocker of the NMDA response versus that (those) activated by KAI. 3. The block by ketamine of excitatory amino acid currents is highly voltage dependent. Concentrations of ketamine that had little effect on outward current responses at depolarized potentials were quite effective at blocking inward current responses at hyperpolarized potentials. In contrast, DL-2-amino-5-phosphonovaleric acid (APV) was equally effective at blocking both inward and outward currents (voltage independent). The voltage dependence of ketamine (a positively charged molecule) could be accounted for if ketamine blocked the NMDA response by binding to a site that experienced 55% of the membrane field. 4. In the presence of ketamine, peak inward currents evoked by repeated applications of NMDA, L-Asp, or L-Glu progressively declined to a steady-state level of block (use-dependent block). This decrement occurred at frequencies much lower than those that were employed to demonstrate desensitization (in the absence of ketamine). Moving the membrane potential to depolarized values did not, in itself, relieve the ketamine block. However, if the appropriate excitatory amino acid (L-Asp, NMDA, L-Glu) was applied during the period of depolarization, a relief of the block could be demonstrated. No recovery from the blockade occurred with periods of rest (no amino acid application) as long as 5 min. Furthermore, no recovery was observed even when ketamine was washed out of the bathing solution until the appropriate agonist was applied. Thus recovery from blockade, like development of blockade, was use dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

20-Oxo-5β-Pregnan-3α-yl Sulfate Is a Use-Dependent NMDA Receptor Inhibitor

“…2 B, C1). The binding characteristics are similar to those described for some of the voltage-dependent blockers of NMDA receptor (MacDonald et al, 1987;Huettner and Bean, 1988). The extent of agonist dependency affects the degree to which the blocker is trapped in the channel, so the blockers range from those that are not trapped [e.g., 9-aminoacridine (Benveniste and Mayer, 1995)] to those that are fully trapped [e.g., MK-801 (Huettner and Bean, 1988)].…”

Structure‐activity analysis of binding kinetics for NMDA receptor competitive antagonists: the influence of conformational restriction

“…In support of this we have found that when 100p1M L-alanine, a rapidly dissociating agonist , is used to activate the glycine recognition site, the kinetics of action of CPP are similar to those measured with 3 pm glycine. The slow recovery from antagonism of NMDA receptor responses evoked by cyclic antagonists could alternatively have a component due to channel block, since drugs such as MK-801, ketamine and desipramine (MacDonald et al, 1987;Huettner & Bean, 1988;Sernagor et al, 1989), which block the ion channel of NMDA receptors, exhibit similar slow kinetics. For this class of drugs both the rate of recovery from block, and potency at equilibrium, show strong voltage dependence.…”

Ketamine, But Not Phencyclidine, Selectively Modulates Cerebellar GABAAReceptors Containing α6 and δ Subunits

“…It has been established that dissociative anesthetics are noncompetitive inhibitors of NMDA excitatory ligand-gated ion channels (Lodge and Anis, 1982;Anis et al, 1983;MacDonald et al, 1987MacDonald et al, , 1991ffrench-Mullen and Rogawski, 1989;Rogawski and Wenk, 2003). These drugs also modulate the activity of nicotinic acetylcholine, muscarinic, and opioid receptors, and voltage-gated ion channels, but at significantly higher concentrations than needed to block NMDA receptors (Finck and Ngai, 1982;Ramoa et al, 1990;Hustveit et al, 1995;Hirota and Lambert, 1996;Scheller et al, 1996;Brau et al, 1997;Furuya et al, 1999;Flood and Krasowski, 2000;Yamakura et al, 2000;Schnoebel et al, 2005).…”