Royal Society Publishing

Inhibitory Miniature Synaptic Potentials in Rat Motoneurons

T. Takahashi


In the newborn rat spinal cord, spontaneous potentials were recorded, with KCl electrodes, from motoneurons in the presence of tetrodotoxin (10$^{-6}$ g ml$^{-1}$) to abolish nerve impulses. These potentials occurred at low frequencies (< 2 Hz), and their mean amplitude was a fraction of 1 m V An increase of osmolarity with sucrose or an increase of extracellular K$^{+}$, increased the frequency of miniature synaptic potentials. The amplitude of the spontaneous potentials was increased by intracellular injection of Cl$^{-}$. Strychnine (2-25 $\mu $M) completely abolished the spontaneous potentials. It is suggested that these potentials are produced by the spontaneous release of packages of inhibitory transmitter at synapses on motoneurons.