Lux H D, Schubert P
Science. 1969 Oct 31;166(3905):625-6. doi: 10.1126/science.166.3905.625.
Long-lasting depolarizing shifts of the electromotive force of post-synaptic inhibition occurred after tracellular injection of ammonium ions, basic amino acids, hydrogen ions, and some bivalent heavy-metal ions. These substances act on specific postsynaptic membrane sites.