Whats the difference between those receptors

[QUARE]

What is the difference between those receptors. Ionotropic receptor, Metabotropic receptor and G protein-coupled receptor.

Basically I know that Ionotropic receptors are are ligant gated ion channel which mean a ligant bind to the receptor to open the channel including those; Na+, K+,Ca²+ and Cl-. Causing an effect which I dont really understand the mechanism. I think Cl- channels are linked to depressant drugs.

What about other receptors ?

 

[sekio]

Based on their structural and functional characteristics, neurotransmitter receptors can be classified into two broad categories: metabotropic and ionotropic receptors. Ionotropic receptors form an ion channel pore. In contrast, metabotropic receptors are indirectly linked with ion channels on the plasma membrane of the cell through signal transduction mechanisms, often G proteins. Hence, G protein-coupled receptors are inherently metabotropic. Other examples of metabotropic receptors include tyrosine kinases or guanylyl cyclase receptors.

Both receptor types are activated by specific neurotransmitters. When an ionotropic receptor is activated, it opens a channel that allows ions such as Na+, K+, or Cl- to flow. In contrast, when a metabotropic receptor is activated, a series of intracellular events are triggered that can also result in ion channels opening but must involve a range of second messenger chemicals.

http://en.wikipedia.org/wiki/Metabotropic_receptor