Abstract
1. Single glass micropipettes were filled with solutions containing various anions and inserted into the soma of the goldfish Mauthner cell (M-cell) and used both for electrophoretic injection of anions and for intracellular recording. In several instances, however, injection of anions and potential recording were made through different barrel of double barreled microelectrodes or through two independent intracellular microelectrodes.
2. The anion injection influenced the spike size as well as the IPSP which were set up by antidromic stimulation of the M-cell.
3. On the basis of the effect upon the IPSP, it was found that the activated inhibitory postsynaptic membrane were permeable to six anion species, Br-, Cl-, NO3-, SCN-, ClO3- and HCOO-, and non-permeable to nine anion species, HS-, BrO3-, HSO3-, HCO3-, CH3COO-, SO4--, H2PO4-, HPO4--and citrate ions. The time constant of the IPSP recovery after injection were assessed for six penetrating anions.
4. A reduction in the spike size was almost always observed after anion injection into the M-cell. The reduction was especially marked after the injection of non-penetrating anions.
5. Antidromic impulse invaded the soma and gave rise to a large spike on top of the usual spike for a short while after the injection of HS- ions. Invasion of impulse activity into the soma membrane has never been reported so far in the M-cell.
6. Results of anion injection in the M-cell were compared with the results obtained in the cat motoneurons.
