Prototypical Features of the Inhibitory Synapses in the Frog Spinal Cord as Revealed Pharmacologically

  • Y. Kudo
  • E. Akiyoshi
Conference paper


Inhibitory synapses of the spinal cord modulate excitatory synaptic transmission and control the tones of agonistic and antagonistic muscles to ensure smooth movements of limbs and fingers. Thus terrestrial vertebrates which are destined to move with their limbs under high gravity are expected to have well organized inhibitory synapses as well as excitatory ones. During studies on the functions of inhibitory synapses in the spinal cord of frog, which is the most primitive terrestrial vertebrate, we encountered many prototypical features. For instance bicuculline and strychnine, well-known antagonists for GABA and glycine in mammalian central nervous system, respectively, showed little antagonism of the GABA- and glycine-induced membrane potential changes in amphibians [6]. Interestingly, we found that these drugs block the effect of taurine which exerts biphasic effects on primary afferent terminals [6]. We have also found that diazepam did not influence GABA binding on synaptic membranes prepared from frog spinal cord [7]. Taurine seems to be a major inhibitory neurotransmitter in the spinal cord of this species. These results give the impression that the inhibitory systems in frog spinal cord are prototypical as compared with those in mammalian central nervous system.


Dorsal Root Ganglion Dorsal Root Dorsal Horn Inhibitory Synapse Mammalian Central Nervous System 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. 1.
    Braestrup C, Honore T, Nielsen M, Petersen EN, Jensen LH (1983) Benzodiazepine receptor ligands with negative efficacy chloride channel coupling. Ad Biochem Psychpharmacol 38: 29–36Google Scholar
  2. 2.
    Joseph BS, Whitelock DG (1968) The morphology of spinal afferent-efferent relationships in vertebrates. Brain Behav Evol 1: 2–18CrossRefGoogle Scholar
  3. 3.
    Krnjevic K (1979) Inhibitory action of GABA and GABA-mimetics on vertebrate neurons. In: Roberts E, Chase TN, Tower DB (eds) GABA in nervous system function. Raven Press New York pp 269–281Google Scholar
  4. 4.
    Kudo Y, Oka J-I, Yamada K (1981) Anisatin, a potent GABA antagonist, isolated from Illicium anisatum. Neurosci Lett 25: 83–88PubMedCrossRefGoogle Scholar
  5. 5.
    Kudo Y, Tanaka A, Yamada K (1983) Dendrobine, an antagonist of j3-alanine, taurine and of presynaptic inhibition in the frog spinal cord. Br J Pharmacol 78: 709–715PubMedGoogle Scholar
  6. 6.
    Kudo Y, Akiyoshi E, Akagi H (1988) Identification of two taurine receptor subtypes on the primary afferent terminal of frog spinal cord. Br J Pharmacol 94: 1051–1056PubMedGoogle Scholar
  7. 7.
    Oka J-I, Fukuda H, Kudo Y (1981) The immaturity of interactions between GABA- and benzodiazepine-binding sites in the frog spinal cord. Gen Pharmacol 12: 385–389PubMedCrossRefGoogle Scholar
  8. 8.
    Pole P, Mohler H, Haeffely W (1974) The effect of diazepam on spinal cord activities: Possible sites and mechanisms of action. Naunyn-Schmiedeberg’s Arch Pharmacol 284: 319–337CrossRefGoogle Scholar
  9. 9.
    Sturman JA, Gaull GE (1976) Taurine in the brain and liver of the development human and Rhesus monkey. In: Huxtable R, Barbeau A (eds) Taurine. Raven Press, New York pp 73–84Google Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 1991

Authors and Affiliations

  • Y. Kudo
    • 1
  • E. Akiyoshi
  1. 1.Department of NeuroscienceMitsubishi Kasei Institute of Life SciencesMachidashi, Tokyo, 194Japan

Personalised recommendations