AP ARTICLE FOR LAB

AP ARTICLE FOR LAB - 6798 Keywords Action potential...

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Journal of Physiology (1997), 505.3 , pp. 617—632 617 Action potential initiation and propagation in rat neocortical pyramidal neurons Greg Stuart*, Jackie Schiller and Bert Sakmann Abteilung Zellphysiologie, Max-Planck-Institut f ur medizinische Forschung, Jahnstrasse 29, D_69120 Heidelberg, Germany 1. Initiation and propagation of action potentials evoked by extracellular synaptic stimulation was studied using simultaneous dual and triple patch pipette recordings from different locations on neocortical layer 5 pyramidal neurons in brain slices from 4-week-old rats (P26—30) at physiological temperatures. 2. Simultaneous cell-attached and whole-cell voltage recordings from the apical trunk (up to 700 ìm distal to the soma) and the soma indicated that proximal synaptic stimulation (layer 4) initiated action potentials first at the soma, whereas distal stimulation (upper layer 2Ï3) could initiate dendritic regenerative potentials prior to somatic action potentials following stimulation at higher intensity. 3. Somatic action potentials, once initiated, propagated back into the apical dendrites in a decremented manner which was frequency dependent. The half-width of back-propagating action potentials increased and their maximum rate of rise decreased with distance from the soma, with the peak of these action potentials propagating with a conduction velocity of approximately 0·5 m s¢. 4. Back-propagation of action potentials into the dendritic tree was associated with dendritic calcium electrogenesis, which was particularly prominent during bursts of somatic action potentials. 5. When dendritic regenerative potentials were evoked prior to somatic action potentials, the more distal the dendritic recording was made from the soma the longer the time between the onset of the dendritic regenerative potential relative to somatic action potential. This suggested that dendritic regenerative potentials were initiated in the distal apical dendrites, possibly in the apical tuft. 6. At any one stimulus intensity, the initiation of dendritic regenerative potentials prior to somatic action potentials could fluctuate, and was modulated by depolarizing somatic or hyperpolarizing dendritic current injection. 7. Dendritic regenerative potentials could be initiated prior to somatic action potentials by dendritic current injections used to simulate the membrane voltage change that occurs during an EPSP. Initiation of these dendritic potentials was not affected by cadmium (200 ìÒ), but was blocked by TTX (1 ìÒ). 8. Dendritic regenerative potentials in some experiments were initiated in isolation from somatic action potentials. The voltage change at the soma in response to these dendritic regenerative events was small and subthreshold, showing that dendritic regenerative events are strongly attenuated as they spread to the soma. 9.
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This note was uploaded on 01/17/2012 for the course CELL BIO & 377 taught by Professor Golfetti during the Fall '11 term at Rutgers.

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AP ARTICLE FOR LAB - 6798 Keywords Action potential...

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