Heterogeneity of pharmacological properties andmRNA expression of neuronal nicotinic acetylcholine receptors in individual intrinsic cardiac neurons

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)

First Committee Member

Charles W. Luetje, Committee Chair


Neurons have the potential to form thousands of distinct neuronal nicotinic receptors from the 8 alpha and 3 beta subunits that are currently known. As a start toward determining which of this vast number of potential receptors are actually present in a single neuron, I examined the nicotinic pharmacological properties and receptor subunit mRNA expression patterns in neurons cultured from rat epicardial ganglia using fura-2 fluorescence imaging and single cell RT-PCR. Analysis of the whole cell pharmacology of these neurons showed a diversity of responses to the agonists acetylcholine and cytisine and to the antagonists $\alpha$-conotoxin-MII and neuronal bungarotoxin suggesting that a heterogeneous population of nicotinic receptor classes, or subtypes, are expressed by individual neurons. Single cell RT-PCR to examine nicotinic receptor subunit mRNA expression by individual neurons revealed that while mRNAs encoding all eight neuronal nAChR subunits for which I probed ($\alpha$2-5, $\alpha$7, $\beta$2-4) were present in multi-cellular cultures, individual neurons express distinct subsets of these nAChR subunit mRNAs. Individual neurons harvested from cultures of rat cardiac parasympathetic ganglia express a diverse and distinct array of subunit mRNAs ranging from simple, $\alpha$3 and $\beta$4, to complex, $\alpha$2, $\alpha$3, $\alpha$4, $\alpha$7, and $\beta$2. The $\alpha$3 subunit and either the $\beta$2 or $\beta$4 or both are expressed by each neuron. Other subunits were expressed in a variable distribution among individual neurons. These results suggest that individual epicardial neurons express distinct arrays of nAChR subunits and that these subunits may assemble into functional receptors with distinct and variable subunit composition. This variable receptor subunit expression provides an explanation for the diversity of pharmacological and biophysical responses in individual neurons.


Biology, Molecular; Biology, Neuroscience; Health Sciences, Pharmacology

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