Undershoots following stimulus-induced rises of extracellular potassium concentration in cerebral cortex of cat
1975; Elsevier BV; Volume: 93; Issue: 1 Linguagem: Inglês
10.1016/0006-8993(75)90286-3
ISSN1872-6240
AutoresUwe Heinemann, Hans Dieter Lux,
Tópico(s)Electrochemical Analysis and Applications
ResumoExtracellular potassium activity (aK) was recorded with potassium-sensitive electrodes in the sensorimotor cortex of cats. Resting activity was 2.8–3.4 mEquiv./l. Electrical stimulation of the cortical surface and the nucleus ventroposterolateralis of the thalamus brough about an increase in aK followed by an undershoot and return to normal value. The lowest observed value of aK was 2.1 mEquiv./l. Size and duration (range 0.5–4 min) of the undershoots of aK increased with increasing peak amplitudes of the preceding rise in aK. Following the rise in aK, a period reduced neuronal activity was observed which was usually shorter lasting than the decrease in extracellular aK. An undershoot of aK and a concomitant reduction of neuronal discharge frequency can also occur in immediate response to antidromic stimulation of the pyramidal tract. To compare the K+ redistribution at normal and reduced levels of aK electrophoretic K+ signals were produced with constant current pulses from a proximate KCl-filled capillary. Both amplitudes and half times of decay of these K+ signals were found to decrease during the phase of poststimulatory undershoot in aK (19 and 23% respectively). It is suggested that an activated reuptake of potassium contributes to the decrease in extracellular aK in addition to inhibitory processes.
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