This immunoassay kit allows for the specific measurement of rat nicotinic acetylcholine receptor,N-AchRs concentrations in cell culture supernates, serum, and plasma.

Nicotinic acetylcholine receptors, or nAChRs, are ionotropic receptors that form ligand gated ion channels in cells plasma membranes. Like the other type of acetylcholine receptors, muscarinic acetylcholine receptors (mAChRs), their opening is triggered by the neurotransmitter acetylcholine (ACh), but they are also opened by nicotine.Also in contrast to muscarinic ACh receptors, nicotinic receptors do not operate with a second messenger, but open themselves forming an ion channel. Their action is inhibited by curare.

Nicotinic acetylcholine receptors are present in many tissues in the body. The neuronal receptors are found in the central nervous system and the peripheral nervous system. The neuromuscular receptors are found in the neuromuscular junctions of somatic muscles; stimulation of these receptors causes muscular contraction.Nicotinic receptors, with a molecular mass of about 280 kDa, are made up of five receptor subunits, arranged symmetrically around the central pore. They share similarities with GABAA receptors, glycine receptors, and the type 3 serotonin receptors, which are all therefore classed into the ionotropic family, or the signature Cys-loop proteins.

Twelve types of nicotinic receptor subunits, α2 through 10 and β2 through 4 (Itier and Bertrand, 2001), combine to form pentamers. The subunits are somewhat similar to one another, especially in the hydrophobic regions. The muscle form of the nAChR consist of two α subunits, a β, a δ and either a γ or an ε. The neuronal forms are much more heterogeneous, with a wide range of possible subunit combinations.

The subunits of the nicotinic receptors belong to a multigene family (16 members in human) and the assembly of combinations of subunits results in a large number of different receptors. These receptors, with highly variable kinetic, electrophysiological and pharmacological properties, respond differently to nicotine, at very different effective concentrations. This functional diversity allows them to take part in two major types of neurotransmission. Classical synaptic transmission involves the release of high concentrations of neurotransmitter, acting on immediately neighbouring receptors. In contrast, paracrine transmission involves neurotransmitters released by synaptic buttons or varicosities, which then diffuse through the extra-cellular medium until they reach their receptors, which may be distant. Nicotinic receptors can also be found in different synaptic locations, for example the muscle nicotinic receptor always functions post-synaptically. The neuronal forms of the receptor can be found both post-synaptically and pre-synaptically.

This assay employs the quantitative sandwich enzyme immunoassay technique. A monoclonal antibody specific for nAChR has been pre-coated onto a microplate. Standards and samples are pipetted into the wells and any nAChR present is bound by the immobilized antibody. An enzyme-linked polyclonal antibody specific for nAChR is added to the wells. Following a wash to remove any unbound antibody-enzyme reagent, a substrate solution is added to the wells and color develops in proportion to the amount of nAChR bound in the initial step. The color development is stopped and the intensity of the color is measured.