There are four main types of membrane receptor:

1. ligand-gated ion channels,
2. tyrosine kinase receptors,
3. guanylate cyclase receptors and
4. G protein-coupled receptors

Ligand-gated ion channel receptors

• generally mediate fast responses
• e.g. nicotinic acetylcholine, GABA-A & GABA-C, glutamate receptors

Tyrosine kinase receptors

• intrinsic tyrosine kinase: insulin, insulin-like growth factor (IGF), epidermal growth factor (EGF)
• receptor-associated tyrosine kinase: growth hormone, prolactin, interferon, interleukin

Guanylate cyclase receptors

• contain intrinsic enzyme activity
• e.g. atrial natriuretic factor, brain natriuretic peptide, nitric oxide

G protein-coupled receptors

• generally mediate slow transmission and affect metabolic processes
• activated by a wide variety of extracellular signals e.g. Peptide hormones, biogenic amines, lipophilic hormones, light
• 7-helix membrane-spanning domains
• consist of 3 main subunits: alpha, beta and gamma