Abstract
Converging lines of behavioral and pharmacological evidence suggest that GABAergic synapses in the basolateral amygdala (BLA) may play an integral role in mediating the anxiolytic effects of ethanol (EtOH). Since anxiety is thought to play an important role in the development of, and relapse to, alcoholism, elucidating the mechanisms through which EtOH modulates GABAergic synaptic transmission in the BLA may be fundamental in understanding the etiology of this disease. A recent study in mice has shown that principal cells within the BLA receive inhibitory input from two distinct types of GABAergic interneurons: a loosely distributed population of local interneurons and a dense network of paracapsular (pcs) GABAergic cells clustered along the external capsule border. Here, we sought to confirm the presence of these two populations of GABAergic synapses in the rat BLA and evaluate their ethanol sensitivity. Our results suggest that rat BLA pyramidal cells receive distinct inhibitory input from local and pcs interneurons and that EtOH potentiates both populations of synapses, albeit via distinct mechanisms. EtOH enhancement of local inhibitory postsynaptic currents (IPSCs) was associated with a significant decrease in paired-pulse ratio (PPR) and was significantly potentiated by the GABAB receptor antagonist SCH 50911 [(+)-(S)-5,5-dimethylmorpholinyl-2-acetic acid], consistent with a facilitation of GABA release from presynaptic terminals. Conversely, EtOH enhancement of pcs IPSCs did not alter PPR and was not enhanced by SCH 50911 but was inhibited by blockade of noradrenergic receptors. Collectively, these data reveal that EtOH can potentiate GABAergic inhibitory synaptic transmission in the rat BLA through at least two distinct pathways.
Footnotes
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This work was supported by National Institutes of Health Grants AA 13960, AA 11997, and AA10422.
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Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
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doi:10.1124/jpet.107.128728.
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ABBREVIATIONS: EtOH, ethanol; BLA, basolateral nucleus of the amygdala; GAD-GFP, glutamate decarboxylase tagged with green fluorescent protein; pcs, paracapsular; IPSC, inhibitory postsynaptic current; QX-314, N-(2,6-dimethyl-phenylcarbamoylmethyl)-triethylammonium chloride; ISI, interstimulus interval; PPR, paired-pulse ratio; PV, parvalbumin; PPD, paired pulse depression; SCH 50911, (+)-(S)-5,5-dimethylmorpholinyl-2-acetic acid; NE, norepinephrine; CeA, central nucleus of the amygdala.
- The American Society for Pharmacology and Experimental Therapeutics
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