A study of the chemokinetic effects of various pharmacological agents upon tetrahymena vorax

1.1. Twenty-eight chemicals were tested for their effect upon the swimming velocity of Tetrahymena vorax, including many neurotransmitter substances together with some of their agonists and antagonists.2.2. Acetylcholine produced a decrease in the forward swimming velocity, acting in a dose dependent manner with a lower threshold concentration of 0.5 × 10−1 M.3.3. The effect of acetylcholine was enhanced by physostigmine (eserine) and antagonized by d-tubocurarine, both of which were capable of producing a response on their own, giving a decrease and increase in forward swimming velocity respectively.4.4. Whole animals were able to hydrolyse exogenously applied acetylcholine at rates that were proportional to the number of individuals present. This reaction was inhibited by 97% in the presence of 10−3 M, physostigmine.