Spreading Depression and Hypoxic Spreading Depression-Like Depolarization Dept.of Physiology,ZUSM LHW
Spreading Depression and Hypoxic Spreading Depression-Like Depolarization Dept. of Physiology, ZUSM LHW
INTRODUCTION Spreading depression(SD)is a striking and highly reproducible response of the gray matter of the central nervous system
INTRODUCTION • Spreading depression (SD) is a striking and highly reproducible response of the gray matter of the central nervous system
SD HSD INTRODUCTION Characteristics of SD At the core of SD is a rapid and nearly complete depolarization of a sizable population of brain cells With massive redistribution of ions between intracellular and extracellular compartments Evolves as a regenerative,“all-or-none'”type process Propagates in the manner of a wave through gray matter
SD & HSD INTRODUCTION • Characteristics of SD ✓ At the core of SD is a rapid and nearly complete depolarization of a sizable population of brain cells ✓ With massive redistribution of ions between intracellular and extracellular compartments ✓ Evolves as a regenerative, “all-or-none” type process ✓ Propagates in the manner of a wave through gray matter
SD HSD INTRODUCTION Normoxic SD can be triggered by high-frequency electrical pulses or direct current mechanical stimuli such as pressure on or puncture of the cortex alkaline pH low osmolarity a variety of chemicals
SD & HSD INTRODUCTION • Normoxic SD can be triggered by ✓ high-frequency electrical pulses or direct current ✓ mechanical stimuli such as pressure on or puncture of the cortex ✓ alkaline pH ✓ low osmolarity ✓ a variety of chemicals
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SD & HSD INTRODUCTION
SD HSD INTRODUCTION ·Hypoxic SD(HSD) A similar response to SD occurs in cerebral gray matter a few minutes after interruption of the blood flow or of the supply of oxygen
SD & HSD INTRODUCTION • Hypoxic SD (HSD) A similar response to SD occurs in cerebral gray matter a few minutes after interruption of the blood flow or of the supply of oxygen
SD HSD INTRODUCTION B o Time no application (min) 30 50 20 20 10 Time from hypoxia(min)
SD & HSD INTRODUCTION
SIMILARITIES BETWEEN SD AND HSD 。The waveform of the△/is essentially identical in SD and HSD,provided that oxygenation is restored shortly after the onset of HSD ·The△V propagate at similar velocities in the tissue during SD and HSD
SIMILARITIES BETWEEN SD AND HSD • The waveform of the Vo is essentially identical in SD and HSD, provided that oxygenation is restored shortly after the onset of HSD • The Vo propagate at similar velocities in the tissue during SD and HSD
SD HSD SIMILARITIES BETWEEN SD AND HSD Ion concentrations change in identical fashion Neurons lose K+and organic anions, including glutamate,to the interstitial fluid Na',Ca2t,and Cl-flow into neurons
SD & HSD SIMILARITIES BETWEEN SD AND HSD • Ion concentrations change in identical fashion ✓ Neurons lose K+ and organic anions, including glutamate, to the interstitial fluid ✓ Na+ , Ca2+ , and Cl– flow into neurons
SD HSD SIMILARITIES BETWEEN SD AND HSD Interstitial space shrinks to the same degree The reduction in membrane potential and input resistance of neurons and glial cells are indistinguishable in the two processes
SD & HSD SIMILARITIES BETWEEN SD AND HSD • Interstitial space shrinks to the same degree • The reduction in membrane potential and input resistance of neurons and glial cells are indistinguishable in the two processes