Acute effects of lithium on synaptic transmission in rat hippocampus studied in vitro

Acute effects of lithium on synaptic transmissions in the CA1 neurones of rat hippocampus were examined. Perfusion of 2-10 mM lithium chloride (LiCl) produced a dose-dependent increase in the amplitude of field EPSPs, whereas change in the population spikes was variable. The increasing ratio of second field EPSP, which was examined by paired-pulse stimulation, was reduced about 10% by 5 mM LiCl. Intracellularly recorded EPSPs and IPSPs were facilitated by 10 mM LiCl, and the soma membrane was depolarized about 3.2 mV. Intracellular calcium concentration was measured in single hippocampal neurones using fura-2. Although calcium concentration at rest was approximately 30 nM and was increased to an average of 220 nM by 10(-5) M glutamate, 10 mM LiCl had no influence on it. The effects of Li on calcium-dependent processes were not manifested in this study. Variable changes of population spikes may be dependent on the balance between the excitatory and inhibitory postsynaptic potentials during lithium application.