GABAergic modulation of primary gustatory afferent synaptic efficacy.

Area of Science:

• Neuroscience
• Sensory Physiology
• Neurotransmission

Background:

• Synaptic transmission modulation is known in somatosensory and olfactory systems.
• The role of GABA in gustatory information processing at the primary afferent synapse is not well understood.

Purpose of the Study:

• To investigate the impact of GABA on gustatory information transmission in goldfish.
• To determine the specific GABA receptors involved in this modulation.

Main Methods:

• Utilized immunocytochemistry for GABA-transporter (GAT-1) to map GABAergic synapses in goldfish vagal lobes.
• Employed an in vitro slice preparation of the vagal lobe to record synaptic field potentials (fEPSPs) in response to gustatory nerve stimulation.
• Applied GABA(A) and GABA(B) receptor agonists (muscimol, baclofen) and antagonists (bicuculline, CGP-55845) to assess their effects on fEPSPs.

Main Results:

• Dense GAT-1 immunoreactivity was observed in the termination layers of primary afferent fibers in the vagal lobe.
• Electrical stimulation evoked fEPSPs mediated by ionotropic glutamate receptors.
• Bath application of GABA(A) and GABA(B) agonists nearly abolished the primary fEPSP.
• GABA receptor antagonists reversed the suppressive effects of the agonists.

Conclusions:

• GABAergic terminals modulate primary gustatory afferent input in goldfish vagal lobes.
• Both GABA(A) and GABA(B) receptors mediate this modulation.
• GABA(B) receptor action likely occurs presynaptically, inhibiting neurotransmitter release.