The influence of high hydrostatic pressure on cocaine and veratrine action in a vertebrate nerve

Interactions of veratrum alkaloids, procaine, and calcium with monolayers of stearic acid and their implications for pharmacological action

The interactions of veratridine, cevadine, veracevine, and veratramine with monolayers of stearic acid show marked differences. Veratridine and cevadine, at concentrations that are known from potential, ionic flux, and other measurements to affect living membranes, react strongly with the film and appear to cause an "interfacial dissolution" whereby both the alkaloid and the stearate leave the surface. Veracevine at the same concentration does not interact with the film. The veratramine reaction is weak, much like that of the local anesthetic procaine. The veratridine and cevadine effects are antagonized by 10^-3M Ca⁺⁺, low pH, and 3.7 and 7.4 x 10^-3M procaine. These differences among the veratrum alkaloids and the antagonisms parallel effects observed in living systems. Such parallelism suggests that similar physical interactions are involved in the stearate film and in natural membranes.

Effects of veratrine and tetrodotoxin on the frog lens potential in normal and calcium-free media

The membrane potentials of posterior fibers of the isolated American bullfrog lens were measured in Ringer solution containing various external Ca2+ concentrations ([Ca]0) by using a conventional glass microelectrode technique. The reduction or removal of [Ca]0 evoked a rapid depolarization of the lens potential whereas the increase of [Ca]0 had almost no effects on the membrane potential. The magnitude of depolarization in Ca2+ -free medium was augmented by adding veratrine but reduced by either the addition of tetrodotoxin (TTX) or the reduction of external Na+ concentration. A slight depolarization still remained after the blockade of Na-channels by adding TTX and developed progressively during a successive exposure of lens to Ca2+-free media. It was concluded that veratrine-sensitive rapid and large depolarization in the frog lens fibers bathed in Ca2+-free medium results from a marked elevation of Na+ permeability but that the TTX-insensitive time-dependent depolarization may depend on the loss of K+ content in lens fibers.

Spinal cord seizures elicited by high pressures of helium

Rats with complete spinal transections were compressed in helium-oxygen to 120 bars. Tremors and increased EMG activity in limbs rostral as well as caudal to the lesions were observed beginning at 30 bars. Spinal seizures occurred at 95 bars, similar to cortical seizure thresholds of intact rats. Denervated limbs remained flaccid throughout the dives. No rostro-caudal progression of symptoms was evident in normal animals, but fluctuation of symptoms with increasing pressure was frequently observed. These findings are consistent with the hypothesis that the effects of pressure on aggregates of neurons exceed those on isolated components.

Physiological Effects of High Pressures of Nitrogen and Oxygen

A brief survey is given of the effects of different pressures on living organisms. High-oxygen partial pressures inhibit oxidative metabolism and, according to Gerschman, have effects which summate at some point with the effects of radiation. In a study of the mechanism of the narcotic effect of inert gases, it was found that high pressures of nitrogen and argon, but not helium, act like other anestheties in favoring water-in-oil rather than oil-in-water emulsion of dilute NaOH solutions and olive oil. The effect is small but appears to be real. This suggests that inert gases may make the lipoidal surface layer of cells relatively more continuous and therefore less permeable.