Premium
THE ROLE OF PRE‐ AND POST‐JUNCTIONAL CHOLINOCEPTORS IN THE ACTION OF NEOSTIGMINE AT THE NEUROMUSCULAR JUNCTION
Author(s) -
Webb Sandra N.,
Bowman W. C.
Publication year - 1974
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1974.tb00533.x
Subject(s) - hexamethonium , fasciculation , neostigmine , chemistry , acetylcholine , neuromuscular junction , antidromic , chloralose , medicine , endocrinology , free nerve ending , anesthesia , cats , neuroscience , electrophysiology , biology
SUMMARY 1. The actions have been compared of the acetylcholine antagonists, hexamethonium, tuborcurarine, pancuronium and gallamine on the effects of neostigmine at the neuromuscular junction of the soleus muscle in cats under chloralose anaesthesia. 2. Neostigmine produced augmentation of twitch tension, muscle fasciculations, repetitive firing in the muscle and antidromic repetitive firing in the ventral roots: all these effects were blocked by the acetylcholine antagonists. The effective doses of hexamethonium were similar to its ganglion blocking doses, being much smaller than those necessary to block the normal soleus twitch, and it is concluded that the effects of neostigmine arise mainly from the action of preserved transmitter (acetylcholine) on the motor nerve endings. 3. In the smallest effective doses, hexamethonium preferentially blocked muscle fasciculations and the associated electrical activity in nerve. Tubocurarine, which has considerable ganglion blocking activity (reflecting its affinity for neuronal cholinoceptors) resembled hexamethonium. In contrast, pancuronium and gallamine, which are considered to have a higher affinity for post‐junctional muscle cholinoceptors, depressed muscle fasciculations only in doses that also depressed twitch augmentation and repetitive firing in muscle. 4. In slightly larger doses, pancuronium and gallamine also blocked antidromic repetitive firing in nerve indicating that these drugs also combine with prejunctional neuronal cholinoceptors, and suggesting that these cholinoceptors are intermediate in character between ganglionic and muscle cholinoceptors.