Memory Impairment and Reduced Exploratory Behavior in Mice after Administration of Systemic Morphine

Abstract

In the present study, the effects of morphine were examined on tests of spatial memory, object exploration, locomotion, and anxiety in male ICR mice. Administration of morphine (15 or 30 mg/kg, intraperitoneally (i.p.)) induced a significant decrease in Y-maze alternations compared to saline vehicle-treated mice. The reduced Y-maze alternations induced by morphine were completely blocked by naloxone (15 mg/kg) or β-funaltrexamine (5 mg/kg) but not by norbinaltorphimine (5 mg/kg) or naltrindole (5 mg/kg), suggesting that the morphine-induced spatial memory impairment was mediated predominantly by μ-opioid receptors (MOPs). Significant spatial memory retrieval impairments were observed in the Morris water maze (MWM) in mice treated with morphine (15 mg/kg) or scopolamine (1 mg/kg), but not with naloxone or morphine plus naloxone. Reduced exploratory time was observed in mice after administration of morphine (15 mg/kg), in a novel-object exploration test, without any changes in locomotor activity. No anxiolytic-like behavior was observed in morphine-treated mice in the elevated plus maze. A significant reduction in buried marbles was observed in morphine-treated mice measured in the marble-burying test, which was blocked by naloxone. These observations suggest that morphine induces impairments in spatial short-term memory and retrieval, and reduces exploratory behavior, but that these effects are not because of overall changes in locomotion or anxiety.

Methoxetamine affects brain processing involved in emotional response in rats

“…In the marble burying test, contrary to anxiolytic (Archer et al, ), antidepressant (Nicolas et al, ) and antipsychotic drugs (Bruins Slot et al, ), MXE increased burying behaviour at low and intermediate doses, with the maximal effect observed at 0.5 mg·kg −1 , while not inducing significant effects at higher doses. The effect of MXE we observed in this test is the opposite of that reported after acute exposure to nicotine (Anderson and Brunzell, ), morphine (Umathe et al, ; Kitanaka et al, ) and cannabinoids (Casarotto et al, ; Deiana et al, ) in mice. Quite unexpectedly, it is also dissimilar from that of NMDA receptor antagonists, which typically reduce marble‐burying behaviour (Egashira et al, ; Iijima et al, ).…”

Deposition of BACE-1 Protein in the Brains of APP/PS1 Double Transgenic Mice

“…Spatial working memory was assessed by recording spontaneous alternation behavior during an 8 min session in a Y maze [ 22 ]. The sequence of arm entries and total number of entries were recorded.…”

Viral-mediated Zif268 expression in the prefrontal cortex protects against gonadectomy-induced working memory, long-term memory, and social interaction deficits in male rats

“…This disparity in locomotor behavior may be due to differences in the size of the testing apparatus. Alternatively, there is some evidence that higher number of arm entries is associated with poor performance in the y-maze (Kitanaka et al, 2015; Ghafouri et al, 2016). This suggests that the increase in arm entries exhibited by the Control/GNX group may be related to their working memory impairments, but this needs to be confirmed experimentally.…”