Enhancement during REM sleep of extracellular potassium ion activity in the reticular formation

Potassium-ion activity in the trigeminal central nervous complex during tooth pulp-evoked slow mass potentials

Following electrical stimulation of the tooth pulp, extracellular K+ activity was enhanced by up to 0.1 mM only in the trigeminal motor nucleus which gave a positive slow mass potential (SMP) of low amplitude. No nuclear region giving a positive or negative SMP of high amplitude showed any detectable change. There are possible generation mechanisms of the negative and positive SMP.

Reticular formation of the lower brainstem. A common system for cardio-respiratory and somatomotor functions. Cross-correlation analysis of discharge patterns of neighbouring neurones

Temporal relations of discharges of 73 pairs of neurones located in the medial parts of the reticular formation of the lower brainstem were studied by cross correlation analyses in chloralose-urethane anaesthetized dogs. The action potentials of 2 or 3 neighbouring neurones were recorded with one electrode simultaneously. Uncorrelated discharges of neurones and 4 different types of correlated discharges were observed in cross correlation histograms: they were: (1) rhythmic couplings with frequencies between 2 and 5 Hz related to the same rhythm in the EEG; (2) strong, non-rhythmic couplings with short latencies up to 5 ms; (3) a combination of strong and rhythmic couplings, and (4) high-frequency oscillation couplings. Most pairs of neurones showed different types of correlation during the recordings. The different forms of correlated discharge behaviour could be related to different types of functional organization of the neuronal network in the reticular formation.

Elevated extracellular potassium concentration in unstimulated spinal dorsal horns of frogs

The extracellular K+ concentration, [K+]e, was studied in unstimulated spinal cords in situ or in isolated spinal cords of frogs. The [K+]e in the dorsal horn at a depth of 150-500 microM exceeded the [K+]e found in the submeningeal fluid, in most of the upper dorsal horn and in the ventral horn by as much as 2.0 mmol . 1(-1). A substantially higher [K+]e, by 0.5-1.0 mmol . 1(-1) was also found in the intermediate region. The blockade of synaptic activity and of spontaneous activity in isolated spinal cords superfused by Ringer solution with high Mg2+ or Mn2+ concentrations decreased [K+]e in the dorsal horn and intermediate region to about 3.0 mmol . 1(-1). Similarly, the increase of spontaneous activity evoked in the isolated cords by changing the temperature of the Ringer solution, was associated with an increase of [K+]e in the dorsal spinal horn. The data suggest that the high [K+]e in the unstimulated dorsal horn results from K+ accumulation during spontaneous activity of interneurones, and its possible physiological role is discussed.