Figure 4.

Electrophysiological analysis of type I cannabinoid (CB₁) receptors. (a) Representative recordings in individual neurons before (baseline) and after the application of 0.3 μM WIN55,212-2 (WIN). (b) Reduction of evoked excitatory postsynaptic current (eEPSC) amplitude by application of various concentrations of WIN (0.1, 0.3, 1.0, 3.0, and 10 μM; n=4–6). Data were fitted using sigmoidal function (eight cells from seven mice for control-artificial cerebrospinal fluid (aCSF); 10 cells from seven mice for control-methyl-β-cyclodextrin (MCD); 10 cells from six mice for 5% krill-aCSF, and eight cells from six mice for 5% krill-MCD). Note that the dose–response curve for WIN was shifted to the left in mice fed 5% krill diet (‘5% krill-aCSF', half-maximal effective concentration (EC₅₀)=0.15±0.08 μM) compared with mice fed control 1 diet (‘control 1-aCSF', EC₅₀=1.52±0.19 μM), and that MCD treatment resulted in a leftward shift of the curve in mice fed control 1 diet (‘control 1-MCD', EC₅₀=0.23±0.05 μM) but not in mice fed 5% krill diet (‘5% krill-MCD', EC₅₀=0.21±0.09 μM). (c) Lower graph, time course of depolarization-induced suppression of excitation (DSE) in the basolateral nucleus of the amygdala (BLA) of mice fed the control 1 and 5% krill diets (12 cells from five mice fed the control 1 diet; 11 cells from five mice fed the 5% krill diet); above, traces show representative recordings in individual neurons. (d) Lower graph, rimonabant (RIM, 5 μM) abolishes the effect of the 5% krill diet on DSE (seven cells from four mice fed the control 1 diet; six cells from three mice fed the 5% krill diet); above, traces show representative recordings in individual neurons. Scale: 5 ms and 50 pA. *P<0.05, one-way analysis of variance (ANOVA) and post hoc Bonferroni comparison. ¹⁾P<0.05 between control-aCSF and control-MCD, P<0.001 between control-aCSF and 5% krill-aCSF; ²⁾P<0.05 between control-aCSF and control-MCD, P<0.01 between control-aCSF and 5% krill-aCSF with one-way ANOVA and post hoc Bonferroni comparison. All experiments in Figure 4 were carried out in the mice to which no behavioral experiments were conducted.