Individual variation in the expression profiles of nicotinic receptors in the olfactory bulb and trigeminal ganglion and identification of α2, α6, α9, and β3 transcripts

doi:10.1016/S0006-2952(99)00326-3

Biochemical Pharmacology

Volume 59, Issue 3, 1 February 2000, Pages 233-240

https://doi.org/10.1016/S0006-2952(99)00326-3 Get rights and content

Abstract

Nicotine evokes dose-dependent and often variable chemosensory responses in animals and humans. Earlier observations that nicotine binds to some nicotinic acetylcholine receptor (nAChR) subtypes in the olfactory bulb (OB) and trigeminal ganglion (TG) led us to investigate the complete nAChR expression profile in each tissue and to determine whether inter-individual differences exist in male and female rats. Total RNA was extracted from individual samples of dissected OB and TG and analyzed by a sensitive reverse transcription–polymerase chain reaction (RT–PCR) assay to determine the messenger RNA profiles of ten transcripts encoded by the α2, α3, α4, α5, α6, α7, α9, β2, β3, and β4 nAChR genes. We found that (a) in the OB, all animals expressed α2, α3, α4, α5, α7, β2, and β4 subunit mRNAs, whereas α6, β3, and α9 transcripts were expressed in only 17, 28, and 33% of the animals, respectively, and (b) in the TG, all animals expressed α2, α3, α6, α7, β2, and β4 subunit mRNAs, whereas α9, β3, α4, and α5 transcripts were expressed in 4, 38, 88, and 92% of the animals, respectively. These results also identified new subunits that are expressed in each tissue (α2, α6, α9, and β3) and demonstrated that individual rats may have different tissue-specific expression profiles for α4, α5, α6, α9, and β3 transcripts. Such variations are likely to be reflected in the composition of functional receptor subtypes in the rat OB and TG that have different activation and desensitization characteristics to acetylcholine and nicotine.

Section snippets

Animals and tissue collection

Naive adult Sprague–Dawley rats (200–400 g, Virus Antibody Free/Plus, Charles River Laboratories) were used in this study. The animals were housed individually in polycarbonate cages in a vivarium with controlled lighting (12 hr light/12 hr dark) and had ad lib. access to food and water. The temperature and relative humidity were maintained at 20–24° and 40–60%, respectively. Rats were anesthetized deeply with 70% CO₂ and then decapitated. After the brain was removed from the skull, the OB and

Multiple neuronal nicotinic receptor subunit mRNAs are expressed in the OB and TG

Analysis of nAChR gene expression in the OB and TG showed individual variation and tissue-specific differences. In the OB, all animals expressed α2, α3, α4, α5, α7, β2, and β4 mRNAs in comparison with 17, 28, and 33% of the animals expressing α6, β3, and α9 mRNAs, respectively. More specifically, one male and two female rats expressed detectable levels of α6 mRNA. The same male rat also expressed a low level of α9 mRNA [see Fig. 1 (top panel) and Table 2].

Several variations in nAChR expression

Discussion

The new information we report here shows that nAChR gene expression varies among individual rats as well as from the OB to the TG. To our knowledge, no study of this nature has been done in sensory tissue of the rat or human despite the general importance of normative tissue differences as well as the need to better understand why some individuals have a greater degree of chemosensitivity to endogenous ACh or nicotine from tobacco products. Although the range for individual chemosensory

Acknowledgements

We thank Sheri Bowman and Walden Hearn for excellent technical assistance and Elyse Jung for DNA sequencing assistance. This project was supported by the UNC-RJR Collaborative Olfactory Research Program.

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^§: Present address of Dr. James C. Walker: FSU-Sensory Research Institute, 1800 E. Paul Dr., Tallahassee, FL 32306-2741.

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Molecular and Cellular PharmacologyIndividual variation in the expression profiles of nicotinic receptors in the olfactory bulb and trigeminal ganglion and identification of α2, α6, α9, and β3 transcripts

Abstract

Section snippets

Animals and tissue collection

Multiple neuronal nicotinic receptor subunit mRNAs are expressed in the OB and TG

Discussion

Acknowledgements

J Biol Chem

Electroencephalogr Clin Neurophysiol

Neurosci Lett

J Chem Neuroanat

Neuroscience

Brain Res

Brain Res Bull

Neurobiol Aging

Brain Res Bull

Neurobiol Aging

Behav Brain Res

Pers Individ Differ

Toxicon

Brain Res

Cell

J Biol Chem

Mol Brain Res

J Biol Chem

Pentameric structure and subunit stoichiometry of a neuronal nicotinic acetylcholine receptor

Nature

Neuronal nicotinic acetylcholine receptors

Olfactory and trigeminal responses to nicotine

Drug Dev Res

Enantiomeric purity of nicotine in tobacco smoke condensate

Med Sci Res

Olfactory discrimination of nicotine-enantiomers by smokers and non-smokers

Chem Senses

Diversity of nicotinic acetylcholine receptors in rat brain. V. α-Bungarotoxin-sensitive nicotinic receptors in olfactory bulb neurons and presynaptic modulation of glutamate release

J Pharmacol Exp Ther

Neuronal nicotinic receptor expression in sensory neurons of the rat trigeminal ganglionDemonstration of α3β4, a novel subtype in the mammalian nervous system

J Neurosci

Molecular and Cellular Pharmacology
Individual variation in the expression profiles of nicotinic receptors in the olfactory bulb and trigeminal ganglion and identification of α2, α6, α9, and β3 transcripts