An electrophysiological analysis of extra-axonal sodium and potassium concentrations in the central nervous system of the cockroach (Periplaneta americana L.).
Simultaneous intracellular and sucrose-gap recordings showed, in contrast to previous findings, that the electrical parameters of giant axons were similar to intact and desheathed connectives bathed with the 'extracellular Ringer' of Yamasaki & Narahashi. This implies that the extra-axonal sodium concentration, in situ, is likely to be lower than had been previously supposed. Axonal responses showed that, despite the high blood concentration of 24-2 mM-K+ measured by flame photometry, the effective concentration in the blood was 10-15 mM-K+ which corresponds to the measurements made with potassium-selective electrodes. The activity of the blood potassium ions caused a marked reduction in the amplitude of the action potentials following surgical desheathing or disruption of the blood-brain barrier with hypertonic urea. It is suggested that a regulatory mechanism exists in the central nervous system which counteracts the effects of the high blood potassium level.
D000200:Action Potentials / Q000187:drug effects*; D000818:Animals; D001369:Axons / Q000502:physiology*; D001812:Blood-Brain Barrier / Q000187:drug effects; D003058:Cockroaches / Q000502:physiology*; D011188:Potassium / Q000097:blood / Q000494:pharmacology*; D012964:Sodium / Q000097:blood / Q000494:pharmacology*; D014508:Urea / Q000494:pharmacology
D014508:Urea; D012964:Sodium; D011188:Potassium