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Catecholamines are produced mainly by the chromaffin cells of the adrenal medulla and the postganglionic fibers of the sympathetic nervous system. Dopamine, which acts as a neurotransmitter in the central nervous system, is largely produced in neuronal cell bodies in two areas of the brainstem: the ventral tegmental area and the substantia nigra, the latter of which contains neuromelanin ...
A dopamine molecule consists of a catechol structure (a benzene ring with two hydroxyl side groups) with one amine group attached via an ethyl chain. [14] As such, dopamine is the simplest possible catecholamine, a family that also includes the neurotransmitters norepinephrine and epinephrine. [15]
Rather than releasing a neurotransmitter, the cells of the adrenal medulla secrete hormones. [ 1 ] The adrenal medulla is the principal site of the conversion of the amino acid tyrosine into the catecholamines ; epinephrine , norepinephrine , and dopamine .
l-DOPA can be directly metabolized by catechol-O-methyl transferase to 3-O-methyldopa, and then further to vanillactic acid. This metabolic pathway is nonexistent in the healthy body, but becomes important after peripheral l-DOPA administration in patients with Parkinson's disease or in the rare cases of patients with AADC enzyme deficiency. [11]
Norepinephrine is a catecholamine and a phenethylamine. [4] Its structure differs from that of epinephrine only in that epinephrine has a methyl group attached to its nitrogen, whereas the methyl group is replaced by a hydrogen atom in norepinephrine. [4]
Some authors include in this category 'putative' adrenergic cell groups, collections of neurons that stain for PNMT, the enzyme that converts norepinephrine to epinephrine (adrenaline). [2] Catecholaminergic cell groups and Parkinson's disease have an interactive relationship. Catecholaminergic neurons containing neuromelanin are more ...
The cell receiving the signal, or target cell, may be another neuron, but could also be a gland or muscle cell. [1] Neurotransmitters are released from synaptic vesicles into the synaptic cleft where they are able to interact with neurotransmitter receptors on the target cell. Some neurotransmitters are also stored in large dense core vesicles. [2]
An adrenergic nerve fibre is a neuron for which the neurotransmitter is either adrenaline (epinephrine), noradrenaline or dopamine. [1] These neurotransmitters are released at a location known as the synapse, which is a junction point between the axon of one nerve cell and the dendrite of another. The neurotransmitters are first released from ...