The effect of chronic oral administration of verapamil on learning and retrieval in rats using passive avoidance learning task

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Abstract

Verapamil is a drug that blocks L-type calcium channels and selectively inhibits calcium ion entry into the central and peripheral nervous system cells. Verapamil is used acutely and chronically in treatment of some cardiovascular and central nervous system disorders. It has also been shown that acute administration of verapamil has no significant effect on learning and memory in rats, but the effect of chronic administration of verapamil on learning and memory has not been fully investigated. Therefore, the purpose of this study was to evaluate the effect of chronic oral administration of verapmil on learning and memory in rats. Male Wistar rats, weighing 150-200 g were used. Rats were treated orally with verapamil for 60 days using oral tube. They were divided into four groups consisting of control and 10, 20, 50 mg/kg of verapamil. After 60 days of treatment with verapamil, animals were trained in a passive avoidance shuttle box, and 24 hours later their memory retrieval were tested. The data indicated that verapamil in all groups had no significant effect on acquisition, but verapamil at a low dose (10 mg/kg) and at a high dose (50 mg/kg) and not at moderate doses (20 mg/kg) significantly reduced memory retrieval (P<0.05 and P<0.01 respectively). These results suggest that chronic administration of verapamil has no significant effect on passive avoidance learning, but at high (50 mg/kg) and low (10 mg/kg) doses and not at moderate dose (20 mg/kg) impairs long term memory in passive avoidance task. It is concluded that verapamil at moderate dose seems to be safe for treatment of cardiovascular and CNS disorders, which needs to be further investigated.