INTRODUCTION The current study aimed at investigating the existence of the cross state-dependent learning between morphine and scopolamine (SCO) in mice by passive avoidance method, pointing to the role of CA1 area. METHODS The effects of pre-training SCO (0.75, 1.5, and 3 μg, Intra-CA1), or morphine (1, 3, and 6 mg/kg, intraperitoneal (i.p.) was evaluated on the retrieval of passive avoidanc...

Introduction: The current study aimed at investigating the existence of the cross state-dependent learning between morphine and scopolamine (SCO) in mice by passive avoidance method, pointing to the role of CA1 area.  Methods: The effects of pre-training SCO (0.75, 1.5, and 3 μg, Intra-CA1), or morphine (1, 3, and 6 mg/kg, intraperitoneal (i.p.) was evaluated on the retrieval of passiv...

Memory and the processes of learning in mammals are well known to be affected by opioid agonists such as morphine, which has been proven to interfere and cause amnesia. The presence of endogenous morphine has been demonstrated in various tissues from mammals to invertebrates. In this study, we have investigated the effects caused by in-vivo immunodepletion of endogenous morphine on working memo...

The modified state dependent retention (MSDR) theory of retrograde amnesia (RA) proposes that the forgetting associated with RA is due to retrieval failure brought about by state dependent memory loss, which is forgetting that occurs when memory recall is attempted in a pharmacological state that differs from the encoding state. In a novel test of the MSDR theory, the current study attempted to...

The present study investigated the effect of morphine sensitization on the impairment of spatial memory retrieval induced by acute morphine in adult male rats. Spatial memory was assessed by 2-day Morris water maze task which included training and test day. On the training day, rats were trained by a single training session of 8 trials. On the test day, a probe trial consisting of 60s free swim...

Introduction: Learning and memory processes result from interaction of neurotransmitter systems in various brain regions such as amygdala and hippocampus. Considering that morphine induces memory impairment, in the current study, we examined the possible role of cholinergic muscarinic receptor s of the central amygdala (CeA) on the morphine-induced amnesia in adult male Wistar rats. Methods: A ...

Four experiments studied anterograde deficits in Pavlovian fear conditioning following prolonged exposure to the mu-opioid receptor agonist morphine. Injections of morphine produced temporally graded anterograde amnesia characterized by deficits in contextual and conditioned-stimulus (CS) conditioning 1 or 7 days and selective impairment in CS conditioning 21 days after last injection. This ant...

Background and Objective: It has been shown that the opioidergic system exerts widespread effects on cognitive functions. Interactions between opioid and serotonin receptors have been reported in some brain structures such as the dorsal hippocampus, thus a functional interaction between opioids and serotonin seems possible concerning memory control. The purpose of this study was to assess the e...