The Action of Strychnine and Nicotine on the Neuromuscular Mechanism of Asterias

I t has been demonstrated that strychninization in Asterias is followed by extreme dorsal flexure of the rays and consequent inability to make righting movements ~ (Figs. 1, 2, and 3). This "spasm" position of the rays is accelerated and accentuated by sensory stimulation. In order to determine the location of the muscles which cause this action, the dorsal, myodermal sheath is cut from all five rays of a specimen of Asterias. This leaves only the ventral floors of the rays attached to the central disk. When such a preparation is put into a solution of strychnine in sea water, the dorsal flexure of the rays takes place, although not so completely as in the intact animal. This result shQws that the ventral walls of the rays contain muscles which act to bend the floor dorsally. The excised pieces of dorsal myodermal sheath when strychninized show dorsal flexure. Therefore, it is evident that in the intact animal, muscles of both the top sheath and floor of the ray act together to flex the ray dorsally. The reverse picture for the entire animal may be obtained by immersing small specimens of Asterias in a solution of alkaloidal nicotine in sea water, concentration 1 : 50,000. Within a few minutes the rays bend downward at the tips and the central disk is raised (Fig. 4), while at the same time the tube feet are completely shortened and withdrawn. The ventral flexure increases in degree until the anima ! is a compact mass (Fig. 5). At this point the starfish falls over on its side, where it remains in the knotted condition shown, for 15 or 20 minutes, after which extension takes place.