Neurotransmitter Plasticity at the Molecular Level

137

In vitro blocking the spontaneous activity of primary cultures of chicken embryo myotubes with tetrodotoxin increases~2-fold their content in surface acetylcholine receptor. To investigate this effect at the level of gene expression, chicken genomic DNA sequences coding for the acetylcholine receptor a subunit were isolated and characterized. They were shown to belong to a single-copy, polymorphic gene with at least two alleles in the chicken strain utilized. Probes derived from these genomic clones were used to quantitate levels of a-subunit mRNA. In culture, a 2-day exposure to tetrodotoxin increased these mRNA levels up to 13-fold, a value similar to that observed after denervation of chick leg muscle (-17-fold). Actin mRNA levels varied little in any of these experiments. These results support the notion that membrane electrical activity affects acetylcholine receptor expression by regulating the accumulation ofthe corresponding mRNAs.The acetylcholine receptor (AcChoR) is an oligomeric protein composed of five transmembrane subunits with an a213y8 structure (reviewed in ref.

Section: Discussionmentioning

confidence: 99%

Activity regulates the levels of acetylcholine receptor alpha-subunit mRNA in cultured chicken myotubes.

Klarsfeld¹,

Changeux²

1985

137

“…Tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating); EC 1.14. 16.2], the rate-limiting enzyme in catecholamine synthesis, has been intensively investigated, and its expression has been found to be controlled by a variety of external factors, both in the developing and adult organism (3,4). For instance, prolonged stimulation of TyrOHase activity has been observed following increased neuronal activity (5,6).…”

mentioning

confidence: 99%

Modulation of tyrosine hydroxylase gene expression in the central nervous system visualized by in situ hybridization.

Bérod¹,

Biguet²,

Dumas³

et al. 1987

A rat tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating); EC 1.14.16.2] cDNA probe was used for in situ hybridization studies on histological sections through the locus coeruleus, substantia nigra, and the ventral tegmental area of the rat brain. Experimental conditions were established that yielded no background and no signal when pBR322 was used as a control probe. Using the tyrosine hydroxylase probe, we ascertained the specificity of the labeling over catecholaminergic cells by denervation experiments and comparison of the hybridization pattern with that of immunoreactivity.The use of35S-labeled probe enabled the hybridization signal to be resolved at the cellular level. A single injection of reserpine into the rat led to an increase of the intensity of the autoradiographic signal over the locus coeruleus area, confirming an RNA gel blot analysis. The potential of in situ hybridization to analyze patterns of modulation of gene activity as a result of nervous activity is discussed.Catecholaminergic cells of the central nervous system are found in small nuclei, mostly in the brain stem and mesencephalon (1, 2). In spite of their paucity (probably <5 x 104 cells) these neurons send projections to nearly every region of the brain and play a crucial role in its function. Tyrosine hydroxylase [TyrOHase; tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating); EC 1.14.16.2], the rate-limiting enzyme in catecholamine synthesis, has been intensively investigated, and its expression has been found to be controlled by a variety of external factors, both in the developing and adult organism (3, 4). For instance, prolonged stimulation of TyrOHase activity has been observed following increased neuronal activity (5, 6). These long-term changes result from a rise in TyrOHase mRNA levels, most probably due to an increase in TyrOHase gene transcription (7,8).In the last decade, the use of TyrOHase antibodies has been instrumental in revealing the organization ofvarious adrenergic, noradrenergic, and dopaminergic cell clusters and pathways in the brain. In the near future, it can confidently be predicted that the histochemical approach will greatly benefit from the availability of cloned cDNA probes. We report here the direct visualization of gene activity and its modulation on rat brain sections at the level ofthe locus coeruleus, the ventral tegmental area, and the substantia nigra. The complementarity of this approach with immunohistochemistry to analyze brain function and plasticity is discussed.MATERIALS AND METHODS Preparation of Probes. The construction and characterization of the recombinant pTH51 clone in plasmid pBR322 have been described (9, 10). The 1758-base-pair insert containing the complete coding and 3'-untranslated sequences was purified by electroelution after agarose gel electrophoresis and labeled by nick-translation (11) with 35S-substituted adenosine and cytidine 5'-[a-thio]-tr...

“…T here is a functional interaction between the immune and nervous systems (1)(2)(3), and substance P (SP) is a major regulatory peptide in this interaction. SP elicits a wide variety of responses in human monocytes͞macrophages.…”

mentioning

confidence: 99%

Full-length and truncated neurokinin-1 receptor expression and function during monocyte/macrophage differentiation

Lai

Kilpatrick

et al. 2006

102