Abstract
Mapping inducible transcription factors has shown that the Edinger-Westphal nucleus is preferentially sensitive to alcohol intoxication. Herein, we characterize the pharmacological and signal transduction mechanisms related to alcohol-induced c-Fos expression in Edinger-Westphal neurons. Using immunohistochemistry, we show that pretreatment with γ-aminobutyric acid (GABA)-ergic antagonists (4 mg/kg bicuculline and 45 mg/kg pentylenetetrazole) attenuates induction of c-Fos expression by alcohol (2.4 g/kg, intraperitoneal). In addition, 10 mg/kg 2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)4,5-dihydro-1H-imidazole (RX 821002), an α2A/D-adrenoceptor antagonist, and 20 mg/kg haloperidol, a dopamine antagonist, also block alcohol-induced c-Fos expression in Edinger-Westphal neurons. No effects were seen in alcohol-induced c-Fos after the pretreatment of 20 mg/kg propranolol (β-adrenoceptor antagonist), 10 mg/kg 2-(2-(4-(2-methoxyphenyl)piperazin-1-yl) ethy)-4,4-dimethyl-1,3-(2H,4H)-isoquinolindione dihydrochloride (ARC 239) (α2B/C-adrenoceptor antagonist), or 30 mg/kg naltrexone (opioid antagonist). Although positive modulators for the GABAA receptor (20 mg/kg 3α-hydroxy-5α-pregnan-20-one and 10–30 mg/kg chlordiazepoxide) and opioid receptor (10 mg/kg morphine) produced significant elevations, agonists for α2-adrenoceptors (clonidine) and dopamine receptors (apomorphine) had no effect on Edinger-Westphal c-Fos expression. These findings suggest that alcohol-induced c-Fos expression in Edinger-Westphal results from direct interactions with GABAA receptors, which are modified by α2A/D-adrenoceptors and dopamine receptors. Also using immunohistochemistry to identify potential intracellular mechanisms associated with alcohol-induced c-Fos expression in Edinger-Westphal, we show time-dependent increases in serine 727 phospho-signal transducer and activator of transcription 3 (Stat3) but no changes in phospho-cAMP response element-binding protein and phospho-Elk1. Time-dependent increases in phospho-extracellular signal-regulated kinase (ERK) 1/2 were found to occur simultaneously with increases in serine 727 phospho-Stat3. Finally, blockade of ERK 1/2 phosphorylation with the mitogen-activated protein kinase (MEK) 1/2 inhibitor SL327 blocked alcohol-induced c-Fos expression, suggesting that alcohol induces c-Fos in Edinger-Westphal neurons through activation of the MEK1/2-ERK1/2-Stat3 pathway.
Footnotes
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This work was supported by National Institute on Alcohol Abuse and Alcoholism Grants AA-13223 and AA-10760 and an N. L. Tartar Trust Fellowship.
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DOI: 10.1124/jpet.102.036046
- Abbreviations:
- ITF
- inducible transcription factor
- EW
- Edinger-Westphal nucleus
- GABA
- γ-aminobutyric acid
- SRE
- serum response element
- Ca/CRE
- calcium/cAMP response element
- SIE
- c-Sis inducible element
- Stat
- signal transducer and activator of transcription
- PBS
- phosphate-buffered saline
- PTZ
- pentylenetetrazole
- 3α5α-P
- 3α-hydroxy-5α-pregnan-20-one
- CDP
- chlordiazepoxide
- TH
- tyrosine hydroxylase
- DMSO
- dimethyl sulfoxide
- ERK
- extracellular signal-regulated kinase
- MEK
- mitogen-activated protein kinase
- VTA
- ventral tegmental area
- CREB
- cAMP response element-binding protein
- LC
- locus coeruleus
- RX 821002
- 2-(2,3-dihydro-2-methoxy-1,4-benzodioxin-2-yl)-4,5-dihydro-1H-imidazole
- ARC 239
- 2-(2-(4-(2-methoxyphenyl)piperazin-1-yl)ethyl)-4,4-dimethyl-1,3-(2H,4H)-isoquinolindione dihydrochloride
- Received March 8, 2002.
- Accepted April 16, 2002.
- The American Society for Pharmacology and Experimental Therapeutics
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