Effects of guanidine on synaptic transmission in the spinal cord of the frog
The effects of guanidine on motoneurons of the isolated frog spinal cord were studied by adding the drug to the solution bathing the cord during intracellular recording. Guanidine (5·10−4 M) did not alter the membrane potential of motoneurons.
The main effect was a marked increase of the amplitudes and frequencies of small spontaneously occurring inhibitory postsynaptic potentials. The hyperpolarizing component of postsynaptic potentials evoked by stimulation of dorsal roots was also enhanced by guanidine. Higher concentrations of guanidine (5·10−3 M) resulted in a very large and irreversible increase of the small spontaneously occurring inhibitory potentials, which now appeared in a regular, rhythmic pattern.
The effects of guanidine could easily be blocked by increasing the magnesium ions (15 mM) in the bath solution.
These results indicate that guanidine facilitates the release of an inhibitory transmitter in afferent terminals of the frog spinal cord either by a direct action on these terminals or indirectly by an action on nerve endings impinging on inhibitory interneurons.
Key wordsGuanidine Transmitter Spinal Cord Amyotrophic lateral sclerosis
Unable to display preview. Download preview PDF.
- Colomo, F., Erulkar, S. D.: Miniature synaptic potentials at frog spinal neurones in the presence of tetrodotoxin. J. Physiol. (Lond.) 199, 205–221 (1968)Google Scholar
- Erulkar, S. D., Dambach, G. E., Mender, D.: The effect of magnesium at motoneurons of the isolated spinal cord of the frog. Brain Res. 66, 413–424 (1974)Google Scholar
- Gergens, E., Baumann, E.: Über das Verhalten des Guanidin, Dicyandiamidin and Cyanamid im Organismus. Arch. Ges. Physiol. 12, 205–214 (1876)Google Scholar
- Kamenskaya, M. A., Elmquist, D., Thesleff, S.: Guanidine and neuromuscular transmission. 1. Effect on transmitter release occurring spontaneously and in response to single nerve stimuli. Arch. Neurol. 32, 505–509 (1975a)Google Scholar
- Kamenskaya, M. A., Elmquist, D., Thesleff, S.: Guanidine and neuromuscular transmission. 2. Effect on transmitter release in response to repetitive nerve stimulation. Arch. Neurol. 32, 510–518 (1975b)Google Scholar
- Katz, B., Miledi, R.: A study of spontaneous miniature potentials in spinal motoneurones. J. Physiol. (Lond.) 168, 389–422 (1963)Google Scholar
- Koizumi, K.: Tetanus and hyperresponsiveness of the mammalian spinal cord produced by strychnine, guanidine, and cold. Am. J. Physiol. 183, 35–43 (1955)Google Scholar
- Lambert, E. H., Elmquist, D.: Quantal components of endplate potentials in the myasthenic syndrome. Ann. N.Y. Acad. Sci. 183, 183–199 (1971)Google Scholar
- Norris, F. H., Calanchini, P. R., Fallat, R. J., Panchari, S., Jewett, B.: The administration of guanidine in amyotrophic lateral sclerosis. Neurology 24, 721–728 (1974)Google Scholar
- Oh, S. J., Kim, K. W.: Guanidine hydrochloride in the Eaton-Lambert syndrome. Electrophysiologic improvement. Neurology 23, 1084–1090 (1973)Google Scholar
- Otsuka, M., Endo, M.: The effect of guanidine on neuromuscular transmission. J. Pharmacol. Exp. Ther. 128, 273–282 (1960)Google Scholar
- Ricker, K., Döll, W.: Treatment of botulism with guanidine. Z. Neurol. 198, 332–341 (1970)Google Scholar
- Scaer, R. C., Tooker, J., Cherington, M.: Effect of guanidine on the neuromuscular block of botulism. Neurology 19, 1107–1110 (1969)Google Scholar
- Simpson, J. I.: Functional synaptology of the spinal cord. In: Frog neurobiology (R. Llinás, W. Precht, eds.), pp. 743–746. Berlin-Heidelberg-New York: Springer 1976Google Scholar
- Sonnhof, U., Richter, D. W., Taugner, R.: Electrotonic coupling between frog spinal motoneurons. An electrophysiological and morphological study. Brain Res. (in press, 1977)Google Scholar
- Sonnhof, U., Grafe, P., Krumnikl, J., Linder, M., Schindler, L.: Inhibitory postsynaptic actions of taurine, GABA and other amino acids on motoneurons of the isolated frog spinal cord. Brain Res. 100, 327–341 (1975)Google Scholar
- Teräväinen, H., Larsen, A.: Effect of guanidine on quantal release of acetylcholine in the mammalian myoneural junction. Exp. Neurol. 48, 601–609 (1975)Google Scholar
- Wiederholt, W. C.: Guanidine hydrochloride therapy in neuromuscular disorders. West. J. Med. 123, 132–133 (1975)Google Scholar