H. Burr Steinbach

Intracellular inorganic ions and muscle action.

Inorganic ions, particularly cations, have long been regarded as potent agents for altering and controlling the activities of living cells. The pharmacological literature is replete with studies on effects of altering environmental concentrations of single ions and of ion ratios. On the basis of such studies, a general feeling has grown up that the ions are important controlling factors, a feeling that is well justified, so far as what may be called surface effects are concerned. However, to deduce from such experiments the roles of intracellular cations may not be justified, and it is with intracellular cations that we are concerned. There is, indeed, very little direct information about the actions of cations within the cells. For example, potassium is well known for its effects on irritabi1it)y and as an agent causing contracture, when supplied in excess in the medium surrounding muscle fibers. However, these effects are usually noted within very short times after the application is made and certainly are not due to any considerable changes in potassium within the fibers themselves. Unless one postulates that all effects, even on the contractile mechanism, are transmitted from the surface inward, i t is necessary to conclude that such studies do not, relate to actions of intracellular cations, but solely to the effects of the extracellular cations, either directly, acting on the surface, or indirectly, in upsett>ing a balance between two phases.

An Unfortunate Event

After Dement and Kleitman (1) first described a low-voltage, fast electroencephalographic sleep cycle in humans, the same type of activity was described in cats by Dement (2) and later by Jouvet et al. (3). We have duplicated this desynchronized sleep electroencephalogram in five of our cats that have been implanted with bipolar electrodes in various deep and surface structures of the brain. These animals have been trained to go to sleep in a sound-proofed room. Behavioral and electroencephalographic arousal thresholds in response to stimulation of the reticular formation are then recorded. The cats exhibited the normal behavioral and electroencephalographic patterns associated with going to sleep, and after 60 or more minutes of complete isolation they drifted into a very high frequency (40 to 50 per second), low amplitude, desynchronized activity (Fig. iB). As described by Jouvet et al. (3), the animals were completely relaxed and deeply asleep. Especially noticeable are the occasional convulsive limb twitches. One of the cats slept with the eyes partially open during this phase. She showed marked nystagmic movements of the eyeball under relaxed nictitating membranes. Although Dement (4) states that he cannot detect changes in arousal threshold between the fastor slow-wave sleep stages, we have found increases in the reticular formation behavioral arousal thresholds of from 1 to 2.5 volts in all of our cats (Fig. 1). This finding confirms Jouvets report (3) of increased auditory and reticular arousal thresholds during this sleep period. One aspect of this desynchronized sleep stage not yet reported is shown in Fig. 1C. Recticular stimulation that