Question

Cannabinoid receptors present principally in the
A) Heart
B) Brain
C) Liver
D) Kidney

Answer 1

According to biological definition a receptor is any structure or site that may be present on the surface of a cell or inside where different ligands can bind. Many times that leads to activation of a signal pathway.

Complete answer:
Cannabinoid receptors are a specific class of receptor that belongs to the G-protein linked receptor superfamily and like the family consists of seven transmembrane domains. The ligands that are known to activate these receptors are- plant cannabinoids, synthetic cannabinoids and endocannabinoids. Cannabinoid receptors are found to be unique for the phylum Chordata. Presently there are two subtypes of cannabinoid receptors, CB1 and CB2. Expression of these receptors occurs at different locations of the body. The CB1 receptor is found to be expressed in the brain, along with kidney, lungs and liver whereas the CB2 receptor is found to be expressed in the hematopoietic and immune system. Later it has been found out that CB2 receptors are also found in the brain. Once the ligand binds to the receptor they are capable of activating many signal transduction pathways. It is capable of exerting its effect on a variety of signalling molecules and pathways such as – protein kinase A and C, calcium channels, ERK, c-jun, JNK etc.

Hence the correct answer is option (B) i.e, Brain.

Note: Cannabinoid receptors are important as they affect various signalling pathways which in turn affects many physiological processes such as appetite, memory, mood and sensation of pain.