The action of camphor on the central nervous system of the squid

Abstract

Newly hatched squid (Loligo pealii) if put into a solution of camphor gum in sea water, 1/10 saturation, show characteristic mantle spasms, involving play of the chromatophores, after a latent period which is about 40 seconds at 24° C. This effect, it has been shown, is due to the action of camphor on the stellar ganglia. 1 In appearance, camphor spasms are indistinguishable from those caused by nicotine. 2 The difference does not lie in the character of the response of the end organs, muscles and chromatophores, but in the locus and the nature of neuronic excitation.

The value of the temperature coefficient Q ₁₀ for the action of camphor, based on the lengths of the latent periods, is 2.4. The function connecting the velocity of the reaction with the concentration of the drug is, for camphor, expressed by v = kC ^1/2 in which , and k is a constant whose value is approximately .75.

The camphor spasms soon pass off and the animals lie inert with chromatophores relaxed. This is not due to paralysis of the end organs for the reason that they may again be thrown into activity by treatment with strychnine or nicotine. The absence of any interference between the action of nicotine and that of camphor may be demonstrated by the following experiment. Let the specimens of squid be immersed in nicotine solution for I minute. They are then put into the solution of camphor. Camphor spasms take place, after which the animals lie quiet for several minutes. At the end of the required latent period 1 nicotine spasms occur just as typically as in animals treated with nicotine alone.