Zinc induces hyperexcitability in the hippocampus

Area of Science:

• Neuroscience
• Neurophysiology
• Biochemistry

Background:

• Zinc is an abundant trace element in the brain, particularly in the hippocampus.
• Its precise role in modulating neuronal excitability and synaptic transmission is complex and not fully understood.

Purpose of the Study:

• To investigate the specific effects of zinc on neuronal excitability in rodent hippocampal slices.
• To determine the impact of zinc on synaptic transmission and identify potential mechanisms of action.

Main Methods:

• Electrophysiological recordings were performed on rodent hippocampal slices.
• A paired-pulse stimulation protocol was used to assess synaptic responses.
• Neuronal excitability was measured by analyzing population spikes and excitatory postsynaptic potentials (EPSPs).
• Varying concentrations of zinc were applied to the perfusate, and effects were observed over time.

Main Results:

• Zinc significantly increased the amplitude of the second population spike in a paired-pulse protocol, while the first spike and EPSPs remained unchanged.
• This effect was dependent on the inter-stimulus interval (8-40 ms) and zinc concentration.
• Prolonged exposure to physiological zinc concentrations induced epileptiform discharges followed by depression.
• The observed effects of zinc on neuronal excitability were mimicked by bicuculline, a GABA-A receptor antagonist.

Conclusions:

• Zinc selectively enhances neuronal excitability in the hippocampus, particularly affecting later synaptic responses.
• The findings indicate that the hippocampal inhibitory system is highly sensitive to zinc.
• Zinc's modulation of neuronal excitability may involve interference with inhibitory neurotransmission, potentially contributing to hyperexcitability and epileptiform activity.