• Proceedings of the Korean Society of Applied Pharmacology
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• 1996.04a
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• pp.180-180
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• 1996

Previous studies have shown that kainic acid (KA) causes an elevation of hippocampal proenkephalin mRNA level. However, the role of proto-oncogene products, such as c-Fos, c-Jun and Fra proteins in the regulation of KA-induced proenkephalin mRNA increase in the hippocampus has not been well characterized. Thus, in the present study, the effect of cycloheximide (CHX) on KA-induced proenkephalin mRNA and immediate early gene products induction was examined. After pretreating with either vehicle or CHX (20 mg/kg, s.c.) for 30 min, KA (10 mg/kg) was administered s.c. The animals were sacrificed 1,2, or 8 hrs after KA administration. Total RNA and were isolated for Northern blot assay, and proteins were isolated for Western and electrophoretic gel-shift assays. First, we found that CHX inhibited KA-induced proenkephalin mRNA increase without altering intracellular proenkephalin protein level. Secondly, Western blot assays showed that KA increased c-Fos, c-Jun and Fra proteins at 1,2, and 8 hrs and CHX inhibited these immediate early gene products. Finally, electrophoretic gel shift assays revealed that KA increased both AP-1 and ENKCRE-2 DNA binding activities. Furthermore, CHX attenuated KA-induced AP-1 and ENKCRE-2 DNA binding activities. Both AP-1 and ENKCRE-2 DNA binding activities were abolished by cold AP-1 or ENKCRE-2 oligonucleotides, and further reduced by antibodies against c-Fos or c-Jun. Antibody against CREB reduced ENKCRE-2, but not AP-1, DNA binding activity. Our results suggest that on-going protein synthesis is required for elevation of hippocampal proenkephalin mRNA level induced by KA. All c-Fos, c-Jun, and Fra proteins appears to be involved in the regulation of hippocampal proenkephalin mRNA level induced by KA (This study was supported by a grant from KOSEF).

• The Korean Journal of Pharmacology
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• v.29 no.2
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• pp.237-244
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• 1993

The effect of nicotine on the secretion of $[Met^{5}]-enkephalin$ (ME) in addition to proenkephalin A (proENK) mRNA levels and effects of indomethacin, nordihydroguaiaretic acid (NDGA), and captopril on nicotine-induced responses were studied in bovine adrenal medullary chromaffrin (BAMC) cells. Long-term exposure of BAMC cells to nicotine at a concentration of $10{\mu}M$ significantly increased proENK mRNA level and the secretion of ME into the medium. Treatment of BAMC cells with NDGA (a lipoxygenase inhibitor, $10{\mu}M$), indomethacin (a cycloooxygenase inhibitor) or captopril (an angiotensin converting enzyme inhibitor) alone did not affect ME secretion and proENK mRNA levels. The pretreatment of BAMC cells with NDGA inhibited the increased ME secretion and proENK mRNA level induced by nicotine. However, indomethacin and captopril did not affect nicotine-induced responses. Our results indicate that neuronal regulations of ME secretion and proENK mRNA level induced by nicotine in BAMC cells are in part mediated by a lipoxygenase-but not cyclooxygenase-and endogenous renin-angiotensin pathway.

• The Korean Journal of Pharmacology
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• v.31 no.1 s.57
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• pp.17-26
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• 1995

The present studies were carried out to determine if antinociceptive action of morphine and ${\beta}-endorphin$ administered intraventricularly was changed in. pentobarbital anesthetized spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Antinociception was assessed by the tail-flick test. The $ED_{50}$ values of antinociception for morphine administered intraventricularly were 1.9 and 1.2 nmol for WKY and SHR rats, respectively. The $ED_{50}$ values of antinociception for ${\beta}-endorphin$ administered intraventricularly were 0.40 and 0.12 nmol for WKY and SHR rats, respectively. The $[Met^5]-enkephalin$ (ME) and proenkephalin mRNA levels in midbrain, pons and medulla, or lumbar section of the spinal cord in WKY and SHR rats were measured by the radioimmunoassay and Northern blot assay, respectively. There were no differences of ME and proenkephalin mRNA levels in these tissues between WKY and SHR rats. The results suggest that ${\beta}-endorphin$ but not morphine administered intraventricularly produces a greater antinociception in SHR rats. This increased antinociceptive effect of ${\beta}-endorphin$ in SHR rats may be not, at least, due to the alterations of ME And proenkephalin mRNA levels in the midbrain, pons and medulla, or spinal cord.

• Toxicological Research
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• v.9 no.2
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• pp.195-206
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• 1993

The expression of proenkephalin (proENK) mRNA and Met-enkephalin (ME) secretion in C6 rat glioma cells and bovine adrenal medullary chromaffin (BAMC) cells were elucidated in the present study. The levels of proENK mRNA and ME secreted into the media in BAMC cells were measured in the presence of cycloheximide and 12-tetrade-canoylphorbol-13-acetate (TPA). Cycloheximide (20 nM) abolished the induction of proENK mRNA expression, protein synthesis and ME secretion by TPA (1nM), indicating that de novo protein synthesis was necessary for proENK gene expression and ME secretion.

• Toxicological Research
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• v.9 no.2
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• pp.187-194
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• 1993

[Met5]-Enkephalin (ME) secretion and the expression of proenkephalin A (proENK) mRNA were studied following long-term exposure of bovine adrenal medullary chromaffin (BAMC) cells to pertussis toxin. Prolonged (24 hr) stimulation of BAMC cells with pertussis toxin increased the secretion of ME as well as proENK gene expression. BAMC cells were also incubated with pertussis toxin in the presence or absence of other secretagogues such as nicotine, angiotensin II and phorbol myristate acetate.