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Biomedical subjects

F Chamas

Publications and source records attributed to F Chamas.

3 recordsLinked to original sources
PubMed1999

Tryptophan hydroxylase mRNA levels are elevated by repeated immobilization stress in rat raphe nuclei but not in pineal gland.

Repeated stress triggers a wide range of adaptive changes in the central nervous system including the elevation of serotonin (5-HT) metabolism and an increased susceptibility to affective disorders. To begin to examine whether these changes are mediated by alterations in gene expression for tryptophan hydroxylase (TPH), the rate-limiting enzyme in 5-HT biosynthesis, we quantitated its mRNA levels by competitive reverse transcription-polymerase chain reaction (RT-PCR). Repeated immobilization stress (2 h, 7 days) elicited a six- or ten-fold rise in TPH mRNA in median raphe nucleus (MRN) and dorsal raphe nucleus (DRN), respectively, without significantly altering TPH mRNA levels in the pineal gland. In contrast, there was little change in mRNA levels for GTP cyclohydrolase I (GTPCH), the rate limiting enzyme in synthesis of the tetrahydrobiopterin (BH4), the obligate cofactor for TPH. This is the first study to reveal stress-elicited activation of TPH gene expression.

Animals↗
PubMed1999

Nicotine infusion modulates immobilization stress-triggered induction of gene expression of rat catecholamine biosynthetic enzymes.

The relationship between nicotine and stress is complex and paradoxical. Although people claim they smoke because it relaxes them, nicotine can trigger some of the effects observed with stress, including the release and synthesis of the catecholamines and their biosynthetic enzymes. This study examined one aspect of this confusing relationship between nicotine and stress. Multiple injections of nicotine bitartrate (5 mg/kg) elevated mRNA levels for the catecholamine biosynthetic enzymes, tyrosine hydroxylase (TH), dopamine beta-hydroxylase (DBH), and phenylethanolamine N-methyltransferase, and of preproneuropeptide Y in rat adrenal medulla more than did 1 mg/kg of nicotine bitartrate. In the locus ceruleus, substantia nigra, and ventral tegmental area both doses equally induced TH mRNA levels. Nicotine infusion (15 mg/kg/day) did not affect adrenal mRNA levels for any of the genes of interest and did not increase plasma corticosterone levels. However, in rats pre-exposed to nicotinic infusions, the response to a single immobilization (IMO) stress was markedly attenuated with respect to changes in adrenomedullary TH, DBH, and phenylethanolamine N-methyltransferase mRNA levels and in c-Fos protein levels. In the central nervous system, the chronic infusion of nicotine prevented the induction of TH mRNA by repeated IMO stress in the ventral tegmental area (but not in substantia nigra) and of DBH mRNA by single IMO in the locus ceruleus. These findings may explain some of the complex interactions between stress and exposure to nicotine.

Adrenal Medulla↗