PHARMACOLOGY - DRUG RECEPTORS 2

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Ligand Gated Receptors - Fastest Acting Receptors.
Examples of Ligand Gated Receptors - GABA - A, Glutamate receptors ( NMDA, AMPA, Kainate), Serotonin (5HT3), Nicotinic receptors.

Nicotinic Receptors - Pentameric Structure.
 Has 2 alpha subunits which acts as a binding site for ACh (Acetylcholine), rest are beta, gamma, delta or epsilon units. The binding of the ACh causes opening of the Sodium channels causing a chain of events. Thus Nicotinic receptors are Ligand gated coupled with sodium channel receptors.

Enzyme linked receptors -  Enzyme inside the cell is linked with the receptor present on the outside.
Examples - Tyrosine Kinase Receptor, Janus Kinase receptor, cGMP receptor, Serine/Threonine Receptor.

Tyrosine Kinase receptor is seen with - VEGF receptors (Vascular Endothelial Growth Factor)
                                                             IGF - 1 Receptor (Insulin like Growth Factor - 1)
                                                             Insulin receptors
Janus Kinase is seen with - Growth hormone receptors
                                             Prolactin and cytokine Receptors

Nuclear receptors -   These are the slowest receptors and are present in the nucleus or in cytoplasm.
Those that present in nucleus are - T3/T4 receptors, Vitamin A receptors, Estrogen Receptors, Progesterone Receptors.
Those that are present in cytoplasm are - Androgen receptors, Vitamin D receptors, Glucocorticoid receptors, Mineralocorticoid receptors.

G - protein coupled receptors -  helical protein that passes 7 times through the cell membrane, Serpentine in nature. Receptors binds to 3 sub-proteins called as Alpha, Beta, Gamma. Alpha binds to GDP and converts GDP to GTP in presence of Phosphate ion (PO4-).
Alpha is the most important part of the whole receptor complex as it has GTPase activity.

Subtypes of Subunits - Gs and Gq
Gs acts as a stimulatory factor to cAMP, where they cause relaxation of smooth muscles and Contraction of cardiac muscles.
Gq acts to stimulate Phospholipase - C. via the IP3, and DAG pathway
IP3 - Inositol Trisphosphate
DAG - Diacylglycerol

Alpha subunit has the following sub-types - 
Gi, Go, G12/13
Gi and Go co-exist, that causes opening of potassium channels leading to relaxations. This has a stimulatory effect on the body but inhibitory effect on heart.
G12/13 acts via the Rho kinase receptor activity,

Some images of receptors, Hover on top of them to know about them.



 


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