Stress-Induced p38 Mitogen-Activated Protein Kinase Activation Mediates κ-Opioid-Dependent Dysphoria

Abstract

The molecular mechanisms mediating stress-induced dysphoria in humans and conditioned place aversion in rodents are unknown. Here, we show that repeated swim stress caused activation of both -opioid receptor (KOR) and p38 mitogen-activated protein kinase (MAPK) coexpressed in GABAergic neurons in the nucleus accumbens, cortex, and hippocampus. Sites of activation were visualized using phosphoselective antibodies against activated receptors (KOR-P) and against phospho-p38 MAPK. Surprisingly, the increase in P-p38-IR caused by swim-stress exposure was completely KOR dependent; P-p38-IR did not increase in KOR(Ϫ/Ϫ) knock-out mice subjected to the same swim-paradigm or in wild-type mice pretreated with the KOR antagonist norbinaltorphimine. To understand the relationship between p38 activation and the behavioral effects after KOR activation, we administered the p38 inhibitor SB203580 [4-(4- fluorophenyl)-2-(4-methylsulfonylphenyl)-5-(4-pyridyl)-1H-imidazole (i.c.v.)] and found that it selectively blocked the conditioned place aversion caused by the agonist trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide (U50488) andthe KOR-dependent swim stress-induced immobility while not affecting -opioid analgesia or nonselectively affecting associative learning. We found that the mechanism linking KOR and p38 activation in vivo was consistent with our previous in vitro data suggesting that ␤-arrestin recruitment is required; mice lacking G-protein-coupled receptor kinase 3 also failed to increase p-p38-IR after KOR activation in vivo, failed to show swim stress-induced immobility, or develop conditioned place aversion to U50488. Our results indicate that activation of p38 MAPK signaling by the endogenous dynorphin--opioid system likely constitutes a key component of the molecular mechanisms mediating the aversive properties of stress.

Activation of the kappa opioid receptor in the dorsal raphe nucleus mediates the aversive effects of stress and reinstates drug seeking

“…Injection of a lentiviral-KOR construct into the DRN was sufficient to restore aversion to a KOR agonist, whereas injection of a construct encoding a mutant receptor (KOR369A) that is unable to activate p38 MAPK (24) did not restore aversive responses. This finding corroborates our report showing that p38 MAPK activation is critical for KOR-dependent CPA (25) and highlights the importance of intracellular MAPK signaling cascades in mediating mood-associated behaviors. The mechanisms by which p38 MAPK activation evokes aversive responses is unknown, however some possibilities are suggested by data Other groups have demonstrated that p38 MAPK contributes to synaptic plasticity by affecting long-term depression (37), possibly through a phosphorylation of proteins including SynGAP and AMPA receptors (38).…”

“…3B). These results confirm that the G␣i functionality of KOR was intact (25), in concordance with reports showing that KOR-mediated ERK activation does not require GRK3 or ␤-arrestin expression (24,26).…”

“…The selective rescue of the antinociceptive response by KOR(S369A) further supports the conclusion that KOR activation in the DRN regulates pain responses. The ability of the KOR(S369A) receptor to restore the analgesic, but not aversive response is consistent with a GRK3/phospho-p38-dependent role of KOR in mediating the aversive response to U50,488 (25). These data also suggest that KOR activation of p38 MAPK in the DRN is sufficient to produce CPA.…”

“…3A, Lower) (21). GRK3 phosphorylation of KOR is necessary for ␤-arrestin-dependent activation of p38 mitogen-activated protein kinase (MAPK) (24), and p38 MAPK activation is required for KOR-dependent aversion (25). A second control lentiviral vector containing only eGFP was generated to assess nonspecific effects of viral-mediated gene transfer on behavior (Fig.…”

6′-Guanidinonaltrindole (6′-GNTI) Is a G Protein-biased κ-Opioid Receptor Agonist That Inhibits Arrestin Recruitment

“…Interestingly, their dysphoric effects require activation of the p38 MAPK pathway mediated by arrestin recruitment to the activated KOR (4, 10, 11). KOR-induced p38 MAPK activation has been demonstrated in heterologous expression systems, striatal neurons and astrocytes, spinal cord astrocytes, and in vivo (12)(13)(14) and requires KOR phosphorylation by the G protein-coupled receptor kinase 3 (GRK3) and subsequent arrestin3 recruitment (12). Based on such findings, Chavkin (11) has proposed that KOR-selective G protein-biased partial agonists that do not efficiently recruit arrestin would not cause dysphoria but would retain sufficient analgesic activity for the treatment of pain-related disorders.…”