Figure 1
Monosynaptic excitatory and polysynaptic inhibitory synaptic transmission in CeLC neurons. (A) Coronal brain slices containing the right amygdala were obtained from normal rats and arthritic rats 4-6 h after injections of kaolin and carrageenan (K/C) into the left knee joint. Magnified area shows position of the patch-clamp electrode ("Recording") in the CeLC; stimulation electrode in the BLA to activate direct glutamatergic projections and indirect disynaptic connections that involve GABAergic neurons in the intercalated cell masses (ITC). Diagrams are from [66]. (B) Biphasic synaptic responses were evoked at different holding potentials (-70, -30, and 0 mV). (C) Individual traces (average of 8-10) of synaptic responses evoked at -70 mV (downward deflections, EPSCs; inhibited by NBQX, 10 μM) and at 0 mV (upward deflections, IPSCs; blocked by bicuculline, 10 μM). Scale bars, 50 pA, 30 ms. (D) Monosynaptic EPSCs, but not polysynaptic IPSCs, follow high-frequency stimulation (20 Hz; 6 individual traces each). Scale bars, 50 pA, 30 ms. (E) Individual EPSCs and IPSCs evoked with twice-threshold stimulation (30 sweeps each). Latencies of IPSCs were longer and more variable. Calibration: 50 pA, 3 ms. (F) Distribution of EPSC and IPSC latencies measured from stimulus artifact to onset of synaptic current in one neuron (n = 100 events). (G) Bar histograms show average latencies (means ± SE) of EPSCs and IPSCs in 10 neurons. ** P < 0.01, paired t-test. (H) Bar histograms show the number of neurons that did not respond to the second or third high-frequency stimulus (HFS, 20 Hz). The failure rate is normalized for each neuron and averaged across the sample of neurons (n = 15; 0, no failure; 1, no IPSC). ** P < 0.01, compared to 1st stimulus (no failure), Dunnett's multiple comparison test.