Final answer:
Increased GABA levels in the brain would likely lead to decreased amygdala activity and suppression of the sympathetic nervous system due to its inhibitory effects on neuronal excitability.
Step-by-step explanation:
In the brain, GABA (gamma-aminobutyric acid) serves as the main inhibitory neurotransmitter, essential in reducing neuronal excitability throughout the nervous system. Concerning a student's question regarding increased GABA levels, well-understood mechanisms suggest that higher concentrations of GABA would lead to amplified inhibitory signals. GABA agonists, such as barbiturates, benzodiazepines, ethanol, and other psychoactive drugs, increase the activity of GABA receptors, reinforcing GABA's inhibitory effect.
Key functions of GABA involve the regulation of anxiety, fear recognition, and counterbalancing excitatory neurotransmitters that are typically involved in the 'fight-or-flight' response. When GABA levels rise, the activation of the sympathetic nervous system is likely to be attenuated due to GABA's ability to dampen the neuronal activity that stimulates this system. An increased GABAergic effect generally calms neuronal activity, which consequently would be expected to reduce overall activity in the amygdala, a region associated with emotional responses such as fear and anxiety.
Therefore, in summary, increased GABA levels in the brain would be expected to decrease amygdala activity and suppress the sympathetic nervous system—an opposite effect to what the student may have initially suggested.