nAChR subunit

Brain expression pattern

Phenotype

References

a2

Ipn, olfactory bulb

Resistant to mecamylamine-induced nicotine withdrawal somatic signs

[22, 28, 71]

a3

Medial habenula, Ipn, VTA, thalamus, pineal

Peripheral symptoms (lethal). Decreased nicotine-induced seizures in heterozygous mice

[23, 29]

a4

Quasi-ubiquitous

Impaired nicotine reward, tolerance sensitization, and self-administration

[27, 99]

a5

Hippocampus CA1, medial habenula, Ipn, VTA, cortex

Resistant to mecamylamine-induced nicotine withdrawal somatic signs, and nicotine-induced seizures and locomotion. a5 knock down in habenula increases nicotine self-administration

[16, 19, 63]

a6

VTA

Impaired nicotine self-administration

 [99]

a7

Quasi-ubiquitous

Increased nicotine induces seizures in gain-of-function mice. Normal nicotine self administration

[25, 99]

b2

Quasi-ubiquitous

Impaired nicotine self-administration, rescued by VTA re-expression

[17, 18]

b3

Medial habenula, VTA, Locus coeruleus

Modulates dopamine release

[14]

b4

Olfactory bulb, medial habenula, pineal

Resistant to mecamylamine-induced nicotine withdrawal somatic signs, and nicotine-induced seizures and locomotion. Habenular overexpression induces nicotine avoidance

[16, 20, 29, 67]