THE ULTRAVIOLET SPECTRA AND NEUROPHYSIOLOGICAL EFFECTS OF "VERATRINE" ALKALOIDS

¹ National Institute of Arthritis & Metabolic Diseases, National Institutes of Health, Public Health Service, Federal Security Agency, Bethesda, Md., and Marine Biological Laboratory, Woods Hole, Mass.

The ultraviolet absorption spectra of veratrine, veratridine, cevadine, cevine, veratraldehyde and tiglaldehyde were determined. These demonstrated (a) that "veratrine" is composed of approximately equal amounts, on a gm. weight basis, of veratridine and of cevadine and (b) that the small acid moieties esterified with cevine are responsible for the characteristic spectra of the veratrine components.

The negative after-potential induced in the squid giant axon, in crab leg nerve, and in the frog sciatic is consistently different in veratridine and cevadine. It decays exponentially in the pure alkaloids, but the initial amplitude is larger in the latter alkaloid and the time constant of decline is considerably longer in the former. By virtue of these distinctive characteristics, the after-potential induced by veratrine demonstrates the presence of the pure alkaloids and, in the squid axon, permits an estimate of the relative amounts.

These alkaloids give rise to repetitive responses to stimuli. In the squid axon this is obviously related to enhanced oscillatory behavior to subthreshold as well as threshold shocks; in the multifibered preparations it is apparently responsible for a "rise phase" of the after-potential, which has never been seen in the single fibers of the squid.

Under conditions of repetitive stimulation the addition of after-potentials in crab nerve shows little difference in cevadine and veratridine except initially. Recovery is slower in the latter. Potassium release under similar conditions is the same in the two alkaloids; reabsorption, which occurs following activity, continues longer in the veratridine.

The possible significance of these results is discussed for the origin of the after-potential and for in vivo effects.