The possibility that zinc (Zn2+) induces giant depolarizing potentials (GDPs) by blocking pre- and postsynaptic γ-aminobutyric acidB (GABAB) receptors in area CAl of rat hippocampal slices was investigated. Monosynaptic GABAA receptor-mediated fast and GABAB receptor-mediated late inhibitory postsynaptic potentials (IPSPs) were evoked in the presence of the excitatory amino acid (EAA) receptor antagonists 6,7-dinitroquinoxaline-2,3-dione (DNQX) and d,l-2-amino-5-phosphonovalerate (APV). Addition of Zn2+ (0.3 mM) resulted in the appearance of long-lasting GDPs which obscured monosynaptic late IPSPs. The GABAA receptor antagonist bicuculline methiodide (BMI; 30 μM) blocked fast monosynaptic IPSPs and GDPs, revealing a monosynaptic late IPSP that was prolonged in the presence of Zn2+ and blocked by the GABAB receptor antagonist CGP 35 348 (100 μM). The selective GABAB receptor agonist baclofen (10 μM) depressed monosynaptic IPSPs and population excitatory postsynaptic potentials (pEPSPs) by acting at presynaptic GABAB receptors. Depression of synaptic potentials by baclofen was unaffected by Zn2+. These results suggest that induction of GDPs in area CAl does not result from an action of Zn2+ at GABAB receptors. We suggest instead that Zn2+ induces GDPs by inducing synchronized discharge of GABAergic interneurons.
|Original language||English (US)|
|Number of pages||4|
|State||Published - Feb 3 1992|
- CGP 35 348
- Giant depolarizing potential
ASJC Scopus subject areas