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Inhibitory transmission in the basolateral amygdala.
D G Rainnie1, E K Asprodini, P Shinnick-Gallagher
1Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77550.
Journal of Neurophysiology
|September 1, 1991
Summary
This study characterizes inhibitory postsynaptic potentials (IPSPs) in basolateral amygdala (BLA) neurons, revealing distinct fast and slow IPSPs mediated by GABAergic and potentially GABAB receptors, influencing neuronal excitability.
Area of Science:
- Neuroscience
- Synaptic Physiology
- Neuropharmacology
Background:
- The basolateral nucleus of the amygdala (BLA) plays a crucial role in emotional processing.
- Understanding inhibitory neurotransmission in the BLA is essential for deciphering its function.
- Synaptic inhibitory postsynaptic potentials (IPSPs) are key modulators of neuronal excitability.
Purpose of the Study:
- To characterize the properties of fast (f-IPSP) and slow (s-IPSP) inhibitory postsynaptic potentials in BLA neurons.
- To determine the receptor mechanisms underlying evoked IPSPs in the BLA.
- To investigate the influence of different stimulation pathways (stria terminalis and lateral amygdala) on IPSP expression.
Main Methods:
- Intracellular recording techniques were employed in BLA neurons.
- Electrical stimulation of the stria terminalis (ST) and lateral amygdala (LA) pathways was used to evoke synaptic responses.
- Pharmacological agents including NMDA and non-NMDA glutamate receptor antagonists (APV, CNQX), and GABA receptor antagonists (BMI, 2-hydroxy-saclofen) were utilized.
Main Results:
- Two distinct IPSP waveforms, biphasic (EPSP-fIPSP) and multiphasic (EPSP-fIPSP-sIPSP), were identified, with waveform expression dependent on stimulation site.
- ST stimulation evoked both biphasic and multiphasic responses, while LA stimulation predominantly evoked multiphasic responses.
- f-IPSPs and s-IPSPs evoked by ST stimulation were sensitive to glutamatergic antagonists, suggesting feed-forward inhibition. LA-evoked f-IPSPs were resistant to CNQX but blocked by BMI, indicating direct GABAergic inhibition.
- f-IPSPs exhibited characteristics of GABAA receptor-mediated potentials, while s-IPSPs suggested GABAB receptor activation.
- The f-IPSP significantly influences BLA neuron excitability and burst firing.
Conclusions:
- BLA neurons receive distinct inhibitory inputs via both GABAA and GABAB receptors.
- The f-IPSP, mediated by GABAA receptors, plays a dominant role in regulating BLA neuronal excitability.
- Feed-forward inhibition, involving glutamatergic transmission, contributes to shaping inhibitory responses in the BLA.