With
oxygen deprivation, the mammalian brain undergoes hyper-activity and neuronal death while this does not occur in the
anoxia-tolerant goldfish (Carassius auratus). Anoxic survival of the goldfish may rely on neuromodulatory mechanisms to suppress neuronal hyper-excitability. As γ-
aminobutyric acid (
GABA) is the major inhibitory
neurotransmitter in the brain, we decided to investigate its potential role in suppressing the electrical activity of goldfish telencephalic neurons. Utilizing whole-cell patch-clamp recording, we recorded the electrical activities of both excitatory (pyramidal) and inhibitory (stellate) neurons. With
anoxia, membrane potential (Vm) depolarized in both cell types from -72.2 mV to -57.7 mV and from -64.5 mV to -46.8 mV in pyramidal and stellate neurons, respectively. While pyramidal cells remained mostly quiescent, action potential frequency (APf) of the stellate neurons increased 68-fold. Furthermore, the GABAA receptor reversal potential (E-
GABA) was determined using the
gramicidin perforated-patch-clamp method and found to be depolarizing in pyramidal (-53.8 mV) and stellate neurons (-42.1 mV). Although
GABA was depolarizing, pyramidal neurons remained quiescent as EGABA was below the action potential threshold (-36 mV pyramidal and -38 mV stellate neurons). Inhibition of GABAA receptors with
gabazine reversed the
anoxia-mediated response. While GABAB receptor inhibition alone did not affect the anoxic response, co-antagonism of GABAA and GABAB receptors (
gabazine and CGP-55848) led to the generation of seizure-like activities in both neuron types. We conclude that with
anoxia, Vm depolarizes towards EGABA which increases APf in stellate neurons and decreases APf in pyramidal neurons, and that
GABA plays an important role in the
anoxia tolerance of goldfish brain.