Endogenous κ Opioid Activation Mediates Stress-Induced Deficits in Learning and Memory

Abstract

We hypothesized that mice subjected to prolonged stress would demonstrate decreased performance in a learning and memory task attributable to the endogenous activation of the opioid receptor (KOR). C57BL/6J mice were tested using the novel object recognition (NOR) assay at various time points after exposure to repeated forced swim stress (FSS). Unstressed mice demonstrated recognition of the novel object at the end of a procedure using three 10-min object interaction phases, with a recognition index (RI) for the novel object of 71.7 Ϯ 3.4%. However, 1 h after exposure to FSS, vehicle-pretreated mice displayed a significant deficit in performance (RI ϭ 58.

Dynorphins Regulate Fear Memory: from Mice to Men

“…Paradoxically, dynorphin exerts its effect on attention through blocking the formation of memories unrelated to the stress situation. In good accordance with the proposed proamnesic role of dynorphins it was shown that dynorphins contribute to stress-induced learning and memory deficits (Carey et al, 2009). …”

“…Dynorphin release helps to fight the stress situation (Knoll and Carlezon, 2010) because it induces analgesia (McLaughlin et al, 2003), regulates the hormonal and behavioral stress responses (McLaughlin et al, 2003;BilkeiGorzo et al, 2008;Schwarzer, 2009) and increases the motivation to avoid stress inducing dysphoria (Bruchas et al, 2007). Dynorphin also impairs memory formation (Carey et al, 2009), therefore it may protect against the generation of intensive stress-related memories. Although it was suggested that it improves focusing of attention to stress-relevant cues (Iordanova et al, 2006), our results now show animals showed a reduced c-fos expression during the extinction phase in the basolateral amygdala, infralimbic cortex and hippocampus.…”

κ-Opioid Receptors in the Central Amygdala Regulate Ethanol Actions at Presynaptic GABAergic Sites

“…Mice lacking KORs drank half as much ethanol as either wild-type (WT) or heterozygous mice (Kovacs et al, 2005), and mice lacking dynorphin also show reduced voluntary ethanol consumption (Blednov et al, 2006). While the mechanistic role of the dynorphin/KOR system in ethanol dependence is not clear, involvement in ethanol abuse and dependence is in line with the well-established role of the dynorphin/ KOR system in stress-induced depression-like behaviors and relapse to drug-seeking behaviors in both rats and mice (Beardsley et al, 2005;Carey et al, 2007Carey et al, , 2009Land et al, 2008).…”

Effects of Conditional Central Expression of HIV-1 Tat Protein to Potentiate Cocaine-Mediated Psychostimulation and Reward Among Male Mice

“…Distance traveled (cm) was recorded using the Noldus EthoVision Pro tracking software as described previously by Carey et al (2009). After 60 min of habituation to the testing arena, mice were administered saline (0.9%, s.c.) or cocaine (10 mg/kg, s.c.) and activity was measured for 30 min.…”