DMSO effects on synaptic facilitation and calcium dependence in bullfrog sympathetic ganglion.
Synaptic transmission in the bullfrog sympathetic ganglion was studied by means of extra- and intracellular recordings. DMSO (3-10%) caused a single orthodromic stimulus to generate a brief burst of repetitive postganglionic discharges. DMSO also partially reversed a preexisting transmission failure in low Ca2+ medium. Ganglia were exposed to gradual reductions in extracellular Ca2+, in the absence and in the presence of DMSO. The recorded amplitude of the postganglionic compound action potential (CAP) was plotted as a function of Ca2+ concentration. In the absence of DMSO transmission failed progressively as Ca2+ was reduced from 1.8 to 0.47 mM but DMSO (3% and 10%) shifted the curve of transmission failure to the left (lower Ca2+ concentration). DMSO inhibits ganglion cholinesterase activity, but this is not the mechanism of its facilitatory effect on Ca2+ entry, since physostigmine did not shift the curve of transmission failure in low Ca2+ to the left. The data suggest that DMSO maintained transmitter release in low Ca2+ by a direct, nonspecific enhancement of Ca2+ influx into the presynaptic nerve terminal.
Matsumoto
M
M
Riker
W K
WK
Takashima
K
K
Goss
J R
JR
Mela-Riker
L
L
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002800:Cholinesterase Inhibitors / Q000494:pharmacology; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D005728:Ganglia, Sympathetic / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D011892:Rana catesbeiana; D013569:Synapses / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects
D002800:Cholinesterase Inhibitors; D002118:Calcium; D004121:Dimethyl Sulfoxide