Effect of anoxia and pharmacological anoxia on whole-cell NMDA receptor currents in cortical neurons from the western painted turtle.

Abstract

The mammalian brain undergoes rapid cell death during anoxia that is characterized by uncontrolled Ca(2+) entry via N-methyl-D-aspartate receptors (NMDARs). In contrast, the western painted turtle is extremely anoxia tolerant and maintains close-to-normal [Ca(2+)](i) during periods of anoxia lasting from days to months. A plausible mechanism of anoxic survival in turtle neurons is the regulation of NMDARs to prevent excitotoxic Ca(2+) injury. However, studies using metabolic inhibitors such as cyanide (NaCN) as a convenient method to induce anoxia may not represent a true anoxic stress. This study was undertaken to determine whether turtle cortical neuron whole-cell NMDAR currents respond similarly to true anoxia with N(2) and to NaCN-induced anoxia. Whole-cell NMDAR currents were measured during a control N(2)-induced anoxic transition and a control NaCN-induced transition. During anoxia with N(2) normalized, NMDAR currents decreased to 35.3%+/-10.8% of control values. Two different NMDAR current responses were observed during NaCN-induced anoxia: one resulted in a 172%+/-51% increase in NMDAR currents, and the other was a decrease to 48%+/-14% of control. When responses were correlated to the two major neuronal subtypes under study, we found that stellate neurons responded to NaCN treatment with a decrease in NMDAR current, while pyramidal neurons exhibited both increases and decreases. Our results show that whole-cell NMDAR currents respond differently to NaCN-induced anoxia than to the more physiologically relevant anoxia with N(2).

• Authors: Damian Seung-Ho Shin, Leslie Thomas Buck
• Journal: Physiological and biochemical zoology : PBZ (Physiol Biochem Zool) 2003 Jan-Feb Vol. 76 Issue 1 Pg. 41-51 ISSN: 1522-2152 [Print] United States
• PMID: 12695985 (Publication Type: Journal Article)

Chemical References

• Receptors, N-Methyl-D-Aspartate
• Dizocilpine Maleate
• Magnesium
• Nitrogen
• Sodium Cyanide

Topics

• Animals
• Cerebral Cortex (cytology)
• Dizocilpine Maleate (pharmacology)
• Electric Conductivity
• Female
• Hypoxia (physiopathology)
• In Vitro Techniques
• Magnesium (antagonists & inhibitors, pharmacology)
• Membrane Potentials (drug effects)
• Neurons (drug effects, metabolism)
• Nitrogen (pharmacology)
• Oxygen Consumption (drug effects)
• Receptors, N-Methyl-D-Aspartate (metabolism)
• Sodium Cyanide (pharmacology)
• Turtles (physiology)