What changes occur in frog oocytes when GABA is introduced?

• A. Hyperpolarization from sodium ions
• B. Depolarization and action potential generation
• C. Hyperpolarization from chloride ions
• D. No significant potential change

Answer: (C)

When GABA is introduced to frog oocytes, the primary change is hyperpolarization due to the influx of chloride ions. GABA (gamma-aminobutyric acid) acts as an inhibitory neurotransmitter in many systems, and when it binds to its receptors, it causes the opening of chloride channels. In the context of frog oocytes, this leads to an increase in intracellular chloride concentration since chloride is typically higher outside the cell than inside. As chloride ions enter the cell, the membrane potential becomes more negative, resulting in hyperpolarization.

This mechanism is significant because it demonstrates how GABA can exert its inhibitory effects, showcasing the role of chloride in regulating the excitability of the neuron or oocyte. Hyperpolarization moves the membrane potential away from the threshold needed to trigger action potentials, effectively reducing neuronal excitability or the activity of other excitable cells.