3-Nitropropionic acid-induced depression of spinal reflexes involves mechanisms different from ischemia-induced depression

• Published in: Brain research bulletin Vol. 77; no. 6; pp. 382 - 387
• Main Authors: Gupta, Rajesh, Deshpande, Shripad B
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16.12.2008
• Subjects: 2-Amino-5-phosphonovalerate - pharmacology; Action Potentials - drug effects; Action Potentials - physiology; Analysis of Variance; Animals; Animals, Newborn; Convulsants - pharmacology; Dose-Response Relationship, Drug; Excitatory Amino Acid Antagonists - pharmacology; Female; Glucose; In Vitro Techniques; Ischemia - chemically induced; Ischemia - physiopathology; Male; Mitochondrial toxin; Monosynaptic reflex; Neural Inhibition - drug effects; Neural Inhibition - physiology; Neurology; Nitro Compounds - pharmacology; Phosphocreatine - analysis; Polysynaptic reflex; Propionates - pharmacology; Rats; Reflex - drug effects; Reflex - physiology; Reflex, Monosynaptic - drug effects; Reflex, Monosynaptic - physiology; Spinal Cord - drug effects; Spinal Cord - physiology; Spinal Nerve Roots - drug effects; Spinal Nerve Roots - physiology; Succinate dehydrogenase; Synaptic transmission; Synaptic Transmission - drug effects; Synaptic Transmission - physiology; Time Factors; Succinate dehydrogenase; Mitochondrial toxin; Monosynaptic reflex; Synaptic transmission; Polysynaptic reflex
• ISSN: 0361-9230; 1873-2747
• DOI: 10.1016/j.brainresbull.2008.09.010

Abstract Effect of 3-nitropropionic acid (3-NPA) and ischemia (glucose- and O2 -free solution) on synaptic transmission in hemisected spinal cord from 4 to 8 day old rats was examined in vitro . Stimulation of a dorsal root (L3-5 segments) evoked monosynaptic (MSR) and polysynaptic reflex (PSR) potentials in the segmental ventral root. Superfusion of 3-NPA (0.17–3.4 mM) depressed the reflexes in a concentration- and time-dependent manner. At 3.4 mM of 3-NPA, the reflexes were abolished by 35 min. Time required to produce 50% depression (T-50) was around 170, 80, 40 and 17 min for MSR and 110, 70, 25 and 16 min for PSR at 0.17, 0.51, 1.7 and 3.4 mM of 3-NPA, respectively. Ischemia also produced a time-dependent depression of reflexes and abolished them by 35 min and the T-50 values were around 18 min. Presence of creatine phosphate (10 mM) in the superfusing medium did not alter the time course of 3-NPA-induced depression of reflexes but prolonged the ischemia-induced depression. dl -2-amino-5-phosphonovaleric acid (NMDA receptor antagonist; 10 μM) failed to block the 3-NPA (3.4 mM)-induced depression of reflexes, but blocked the ischemia-induced depression. The results indicate that 3-NPA-induced depression of spinal reflexes does not involve NMDA receptors and is different from ischemia-induced depression.