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Dendrobine, an antagonist of β‐alanine, taurine and of presynaptic inhibition in the frog spinal cord
Author(s) -
Kudo Yoshihisa,
Tanaka Atsuko,
Yamada Kiyoyuki
Publication year - 1983
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1983.tb09424.x
Subject(s) - antidromic , chemistry , strychnine , hyperpolarization (physics) , neuroscience , stimulation , biochemistry , biology , stereochemistry , nuclear magnetic resonance spectroscopy
1 The effects of dendrobine and nobiline, alkaloids isolated from Dendrobium nobile , on the electrical activity and on amino acid‐induced depolarizations of primary afferent terminals were tested on the frog isolated spinal cord and were compared with those of picrotoxinin and strychnine. 2 Dendrobine (3 × 10 −5 m ) caused a slight hyperpolarization in both dorsal and ventral roots and this hyperpolarization was accompanied by the augmentation of the dorsal root potential (DR‐DRP) and the ventral root potential and reflex (DR‐VRP and DR‐VRR). The amplitude of the dorsal root reflex (DR‐DRR) however, was reduced significantly. Nobiline (3 × 10 −5 m ) had no significant effect on either the root potentials or the reflexes. 3 Dendrobine (3 × 10 −5 m ) reduced the dorsal root potential induced by repetitive antidromic stimulation of ventral root (VR‐DRP) as well as diminishing the maximum rate of rise of the dorsal root potential induced by the stimulation of adjacent dorsal roots (DR‐DRP), during which time the amplitude of the DR‐DRP was seen to be augmented. 4 Dendrobine (3 × 10 −5 m ) reduced the β‐alanine‐ and taurine‐induced depolarizations of primary afferent terminals, while having little effect upon GABA‐ and glycine‐induced depolarizations. 5 Dendrobine (10 −5 m ) reversibly blocked the presynaptic inhibition caused by antidromic conditioning stimulation of the ventral root. 6 These effects of dendrobine were qualitatively similar to those of strychnine but were somewhat different from those of picrotoxinin, a molecule having the same picrotoxane skeleton. 7 The present results are discussed with reference to the likely neurotransmitters involved in presynaptic inhibition in the frog spinal cord, and with respect to the structure‐activity relationship of picrotoxane compounds as amino acid antagonists.