Influence of diltiazem on the behavior of zolpidem-treated mice in the elevated-plus maze test

The present study was undertaken to investigate the effect of diltiazem, a L-type calcium channel blocker (CCB), on the behavior of zolpidem-treated mice in the elevated plus-maze (EPM). Atypical benzodiazepine zolpidem significantly increased the percentage of open arm entries without influencing the total entries and total distance and average speed at the dose of 5 mg/kg (p.o.). Co-administration of zolpidem (2 mg/kg, p.o.) and diltiazem (5, 10 and 20 mg/kg, p.o.) significantly increased both the time spent and arm entries in the open arms without influencing the total entries and spontaneous activity notwithstanding that zolpidem at dose up to 2 mg/kg (p.o.) and diltiazem at dose up to 20 mg/kg (p.o.) did not show any effects on mice behavior in EPM. Zolpidem also attenuated the anxiogenic effect of 1-(3-Chlorophenyl)piperazine (mCPP, 0.7 mg/kg, i.p.) and 5-hydroxytryptophan (5-HTP, 30 mg/kg, i.p.). Even though the zolpidem at 1 mg/kg and diltiazem at 5 mg/kg were ineffective on mCPP-induced anxiety, respectively, the co-administration of zolpidem (1 mg/kg, i.p.) and diltiazem (5 mg/kg, p.o.) showed inhibitory effect on mCPP-induced anxiety in mice. These results suggested that diltiazem, a L-type CCB may augment the anxiolytic-like effect of zolpidem and also indicated that calcium channel modulation maybe involved in the anxiolytic-like properties of zolpidem.