Effects of replacing extracellular chloride with formate on the inhibitory neuromuscular junction of the crayfish opener muscle.
The effect of partially replacing extracellular chloride by formate on the inhibitory junction of the crayfish opener muscle is investigated. Inhibitory postsynaptic potential (IPSP) amplitude, recorded in muscle fibers and presynaptic axons, increases significantly in the formate saline whereas input resistance and resting membrane potential of muscle fibers are not affected. The increase in IPSP amplitude is mainly due to an increase in IPSP driving force while the GABA mediated conductance change underlying IPSP is not altered. The waveform of presynaptic action potential is slightly altered by formate substitution where an after-depolarizing potential is decreased. This change does not seem to affect the probability of transmitter release because the magnitude of synaptic facilitation is unchanged. In conclusion, formate substitution significantly increases IPSP amplitudes by increasing its driving force without affecting presynaptic release mechanisms.
Nguyen
D
D
Department of Biology, Boston University, MA 02215, USA.
Lin
J W
JW
D000818:Animals; D003400:Astacoidea; D002712:Chlorides / Q000494:pharmacology*; D005561:Formates / Q000494:pharmacology*; D008564:Membrane Potentials / Q000187:drug effects; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000294:innervation; D009433:Neural Inhibition / Q000187:drug effects*; D009469:Neuromuscular Junction / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects
D002712:Chlorides; D005561:Formates