DRUGS ACTING ON ANS
The drugs acting on the autonomic nervous system is known as Autonomic drugs. They are mainly classified as
1. Adrnergic drugs 2. Cholinergic drugs
ADRENERGIC NEURO TRANSMITTERS
Adrenergic nerves release the neurotransmitters like Nor Epinephrine(Nor Adrenaline), Epinephrine(Adrenaline) and Dopamine.
Structure and Physico chemical Properties:
1.Nor Epinephrine(Nor Adrenaline)
It is a neurotransmitter of post ganglionic sympathetic neurons. As a result of sympathetic nerve stimulation, it is released from sympathetic nerve endings in to the synoptic cleft, where it interacts with specific pre synoptic and post synoptic Alpha and beta adrenergic receptors. It has chiral carbon and exist as enantiomeric pair of isomers.The drugs acting on the autonomic nervous system is known as Autonomic drugs. They are mainly classified as
1. Adrnergic drugs 2. Cholinergic drugs
ADRENERGIC NEURO TRANSMITTERS
Adrenergic nerves release the neurotransmitters like Nor Epinephrine(Nor Adrenaline), Epinephrine(Adrenaline) and Dopamine.
Structure and Physico chemical Properties:
1.Nor Epinephrine(Nor Adrenaline)
2.Epinephrine(Adrenaline)
It is not released from nerve endings, but synthesized and stored in the adrenal medulla, from which it is released in to the circulation. Epinephrine is also biosynthesized in certain neurons of the CNS. It belongs to the chemical class of substances known as catecholamines. They are easily oxidized in the presence of air or other oxidizing agents. So they are stabilized by anti oxidants such as ascorbic acid or sodium bi sulphite. It has chiral carbon and exist as enantiomers. Catecholamines are polar substance that contain both acidic(Phenolic -OH) and basic(Aliphatic amine) has pKa values 8.7 and 9.9.
3.Dopamine
It is a neurotransmitter in the basal ganglia of CNS. Dopamine b- hydroxylase enzyme converts dopamine in to nor epinephrine. The enzyme is not presnt in dopaminergic neuron. Hence it remains in original form to carry out the function of neuro transmitter.
Bio synthesis of neuro transmittersThe biosynthesis of catecholamines, Dopamine, Nor epinephrine and Epinephrine involves a sequence of enzymatic reactions.
Catecholamine biosynthesis takesplace in adrenergic and dopaminergic neurons in CNS, in sympathetic neurons of the ANS and in the adrenal medulla.
The aminoacid L-Tyrosine serves as the precursor for the catecholamines. It is acted by tyrosine hydroxylase to form L-dihydroxy phenyl alanine(L-dopa). The second step is the decarboxylation of L-Dopa to dopamine by L-aromatic aminoacid decarboxylate. Then this dopamine is hydroxylated by b- Mono oxygenase in presence of Cu2+ to give Nor epinephrine.
The bio synthesis is represented as follows.
Catecholamine biosynthesis takesplace in adrenergic and dopaminergic neurons in CNS, in sympathetic neurons of the ANS and in the adrenal medulla.
The aminoacid L-Tyrosine serves as the precursor for the catecholamines. It is acted by tyrosine hydroxylase to form L-dihydroxy phenyl alanine(L-dopa). The second step is the decarboxylation of L-Dopa to dopamine by L-aromatic aminoacid decarboxylate. Then this dopamine is hydroxylated by b- Mono oxygenase in presence of Cu2+ to give Nor epinephrine.
The bio synthesis is represented as follows.
Metabolism
The actions of adrenaline and nor adrenaline are terminated by the following three process.
Reuptake in the nerve terminal
Dilution by diffusion from the junctional cleft and uptake at non neuronal sites.
Metabolic transformation.
Two enzymes namely mono amino oxidase (MAO) and Catechol-O-Methyl Transferase (COMT) are important for the biotransformation of catecholamines. These enzymes are distributed through out the body.
