CB1
Cannabinoid receptor type 1 (CB1) receptors are thought to be one of the most widely expressed G protein-coupled receptors in the brain. This is due to endocannabinoid-mediated depolarization-induced suppression of inhibition, a very common form of short-term plasticity in which the depolarization of a single neuron induces a reduction in GABA-mediated neurotransmission. Endocannabinoids released from the depolarized post-synaptic neuron bind to CB1 receptors in the pre-synaptic neuron and cause a reduction in GABA release.
They are also found in other parts of the body. For instance, in the liver, activation of the CB1 receptor is known to increase de novo lipogenesis. Activation of presynaptic CB1 receptors is also known to inhibit sympathetic innervation of blood vessels and contributes to the suppression of the neurogenic vasopressor response in septic shock.
A study done on CB1 knockout mice (genetically altered mice that cannot produce CB1) showed an increase in mortality rate. They also displayed suppressed locomotor activity as well as hypoalgesia (decreased pain sensitivity). The CB1 knockout mice did respond to Delta9-Tetrahydrocannabinol THC. This shows that either CB2 or unknown cannabinoid receptors also have pharmacologic significance.
Read more about this topic: Cannabinoid Receptor