Long-term depression in the basolateral amygdala of the mouse involves theactivation of interneurons

Long-term depression (LTD) in the basolateral amygdala, following low frequ ency stimulation (1 Hz/900 pulses) of the lateral amygdala, was studied in an in vitro slice preparation of 2-3 weeks and 2-4 months old mice. Whole-c ell patch-clamp recordings of neurons, visualized by means of infrared vide omicroscopy. and extracellular field potential recordings were performed. L oading single neurons with the calcium chelator BAPTA (30 mM) did not reduc e the excitatory postsynaptic currents following low frequency stimulation. However, buffering presynaptic calcium with BAPTA-AM, and application of t he specific Ca2+/calmodutin-stimulated protein kinase II antagonist KN-62 ( 1-[N,O-bis(5-isoquinoline sulfonyl)-N-methyl-L-tyrosyl]-4-phenylpiperizine) , blocked low frequency stimulation-induced LTD, The induction of LTD was r educed by the competitive N-methyl-D-aspartate receptor antagonist D-(-)-2- amino-5-phosphonopentanoic acid (50 muM), and blocked by the metabotropic g lutamate receptor antagonist (-)-amino-4-carboxymethyl-phenylacetic acid (1 mM), and by 5-hydroxytryptamine (5-HT; 30 muM) via the activation of 5-HT1 A receptors. Also blocking GABA(A) receptor-mediate synaptic transmission w ith bicuculline (10 muM) or picrotoxin (20 muM) reduced the induction of LT D. Visually and electrophysiologically identified interneurons in slices fr om 2 weeks old mice, expressed in contrast to adult mice (2-4 months), pron ounced LTD. Principal neurons showed only weak LTD after low frequency stim ulation. A synopsis of these findings suggests a pivotal role of GABAergic interneur ons and serotonergic afferents in the induction of LTD in the basolateral n ucleus of the amygdala. (C) 2001 IBRO. Published by Elsevier Science Ltd. A ll rights reserved.