The selective effect of some chemical stimuli on reflexes from chemoreceptors

Summary

Short-term experiments on cats under urethane anesthesia were performed. The effect of streptomycin introduced parenterally was studied on reflexes from chemoreceptors of the spleen, kidney and hind limb. Chemoreceptors were stimulated by acetylcholine, nicotine and carbon dioxide which were introduced into the fluid perfusing these organs, isolated from the general circulation but connected to the organism by the nerves. It was established that streptomycin in a dose of 60,000 to 200,000 units completely eliminates or markedly depresses the reflexes from chemoreceptors when introduced intramuscularly; the maximal effect of the antibiotic is most frequently seen at the end of the first hour or during the second following the intramuscular injection, and during the first hour after intravenous injection. However, the reflexes which appeared in stimulation of the central portion of the large tibial nerver by induction current in the same experimental conditions were different from the reflexes coming from chemoreceptors. They either did not change at all, or showed only slight increase or decrease. Sometimes these reflexes were subjected to pronounced depression. However, this occurred only when large doses of the antibiotic were used at the late stages of its action and to a lesser degree than the reflexes from the chemoreceptors. The authors comes to the conclusion that streptomycin has a marked neurotropic effect, which is manifested in depression of the part of the chemoreceptor reflex arc located in the central nervous system.