PHARMACOLOGY

 IMPACT OF MOLECULAR PHARMACOLOGY IN UNDERSTANDING MECHANISMS AND DEVELOPMENT OF NEW DRUGS ::

Radioreceptor ligand binding studies paved way to isolate and purify the receptors it begain with affinity chromatography using specific antagonists Receptor ligand is covalently bound to the matrix of chromatography column This adsorbs the receptors and these adsorbed receptors may be eluted from the column by flushing through a solution containing specific antagonist e.g. gallamine for nicotinic receptors 

            Receptors once isolated and purified are characterized for their amino acid sequences when amino acid sequences are known one can find out corresponding base sequences of mRNA Oligonucleotides probes are then synthesized and used to extract the full length DNA sequence by conventional cDNA Complementary DNA  cloning methods The first receptor clones were obtained in this way and now there are many alternate stategies used for example expression or cloning of receptors makes the use of cDNA vector /host system that allows the production of protein encoded by the cDNA If the proteins are expressed directly in a bacterial cell antibodies against the receptor protein may be used to detect bacterial clones carrying the correct cDNA It is also possible to introduce foreign DNA into mammalian cell lines by transfection and to monitor receptor expression by the appearance of specific ligand binding This technique is used to study binding and pharmacological characteristics of receptors Lastly using cloning techniques PCR (polymerase chain reaction ) and RACE (rapid amplification of cDNA ends) it has been possible to identify various receptor subtypes and unknown receptors (Orphan receptors )