Post‐stimulus hyperpolarization and slow potassium conductance increase in Aplysia giant neurone

Abstract

SUMMARY1. Intracellular records from Aplysia giant (R 2) cell somata showed long lasting 4-10 mV hyperpolarizations after passage of outward current through a second intracellular electrode.2. An increase in membrane slope conductance occurred simultaneously with the post-stimulus hyperpolarization (PSH).3. Both the PSH and conductance-increase varied strongly with stimulus amplitude and duration.4. Both the PSH and the conductance increase occurred in Ca-free medium containing tetrodotoxin, when action-potential production was completely blocked.5. The PSH persisted in the presence of ouabain or DNP, with cooling, with removal of external K+, and in media where all the Na+ was replaced with Li+, suggesting that it was not due to the activity of an electrogenic pump.6. A reversal potential for the PSH was demonstrated by application of maintained inward current following the end of an outward-directed stimulus.7. The PSH reversal potential varied with [K]o, but not with [Cl]o or [Na]o, suggesting that the PSH was mainly due to an increase in K conductance.8. The PSH and the conductance increase were reduced strongly when all the Na+ was replaced with Tris, and only slightly when Na+ was replaced with sucrose.

Slowly activating K + channels in rat olfactory receptor neurons

“…Slow currents due to electrogenic ion pumps, external K+ accumulation or to conductances activated by the progressive intracellular accumulation of Ca2+ or other ligands are more commonly observed. However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron.…”

“…However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron. Partridge & Stevens (1976) and Krylov & Makovsky (1978) have shown a role for slow K+ currents in spike frequency adaptation.…”

Slowly activating K + channels in rat olfactory receptor neurons

“…Slow currents due to electrogenic ion pumps, external K+ accumulation or to conductances activated by the progressive intracellular accumulation of Ca2+ or other ligands are more commonly observed. However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron.…”

“…However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron. Partridge & Stevens (1976) and Krylov & Makovsky (1978) have shown a role for slow K+ currents in spike frequency adaptation.…”

In vitro tests for a circadian rhythm in the electrical activity of a single neuron inAplysia californica

“…The depression of activity in i{15 following cessation of the EPSP stimulus is similar to a post stimulation hyperpolarization (PSH) reported by several authors in R2 in Aplysia (Brodwick and Junge, 1972), Tritonia (Junge, 1972) and leech (Jansen and Nicholls, 1973). In Tritonia Junge found that the PSI-I was due to an increase in potassium conductance.…”

Cyclic variation of potassium conductance in a burst‐generating neurone in Aplysia

“…The DNP evidently produced irreversible changes in the cell, as no recovery of bursting was ever obtained after treatment with DNP, even with repeated saline washes. A similar harmful effect of DNP has also been noted on the giant (R 2) cell (Brodwick & Junge, 1972). However, during the first 15 min or so in DNP, after the depolarizing action had occurred, the bursting pattern of the R 15 cell continued in a normalappearing manner.…”

Slowly activating K + channels in rat olfactory receptor neurons

“…Slow currents due to electrogenic ion pumps, external K+ accumulation or to conductances activated by the progressive intracellular accumulation of Ca2+ or other ligands are more commonly observed. However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron.…”

“…However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron. Partridge & Stevens (1976) and Krylov & Makovsky (1978) have shown a role for slow K+ currents in spike frequency adaptation.…”

In vitro tests for a circadian rhythm in the electrical activity of a single neuron inAplysia californica

“…The depression of activity in i{15 following cessation of the EPSP stimulus is similar to a post stimulation hyperpolarization (PSH) reported by several authors in R2 in Aplysia (Brodwick and Junge, 1972), Tritonia (Junge, 1972) and leech (Jansen and Nicholls, 1973). In Tritonia Junge found that the PSI-I was due to an increase in potassium conductance.…”

Cyclic variation of potassium conductance in a burst‐generating neurone in Aplysia

“…The DNP evidently produced irreversible changes in the cell, as no recovery of bursting was ever obtained after treatment with DNP, even with repeated saline washes. A similar harmful effect of DNP has also been noted on the giant (R 2) cell (Brodwick & Junge, 1972). However, during the first 15 min or so in DNP, after the depolarizing action had occurred, the bursting pattern of the R 15 cell continued in a normalappearing manner.…”

Slowly activating K + channels in rat olfactory receptor neurons

“…Slow currents due to electrogenic ion pumps, external K+ accumulation or to conductances activated by the progressive intracellular accumulation of Ca2+ or other ligands are more commonly observed. However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron.…”

“…However, there is evidence for a K+ conductance in some molluscan neurons which does not appear to be influenced by these effects and which activates with a similar voltage range and timecourse to the channels reported in this study (Brodwick & Junge 1972;Partridge & Stevens 1976). Brodwick & Junge (1972) found that this current produced a slow after-hyperpolarization following repetitive activation of the neuron. Partridge & Stevens (1976) and Krylov & Makovsky (1978) have shown a role for slow K+ currents in spike frequency adaptation.…”

In vitro tests for a circadian rhythm in the electrical activity of a single neuron inAplysia californica

“…The depression of activity in i{15 following cessation of the EPSP stimulus is similar to a post stimulation hyperpolarization (PSH) reported by several authors in R2 in Aplysia (Brodwick and Junge, 1972), Tritonia (Junge, 1972) and leech (Jansen and Nicholls, 1973). In Tritonia Junge found that the PSI-I was due to an increase in potassium conductance.…”

Cyclic variation of potassium conductance in a burst‐generating neurone in Aplysia

“…The DNP evidently produced irreversible changes in the cell, as no recovery of bursting was ever obtained after treatment with DNP, even with repeated saline washes. A similar harmful effect of DNP has also been noted on the giant (R 2) cell (Brodwick & Junge, 1972). However, during the first 15 min or so in DNP, after the depolarizing action had occurred, the bursting pattern of the R 15 cell continued in a normalappearing manner.…”