NEUROTRANSMITTERS
Acetylcholine
Binds to nicotinic acetylcholine receptors which are transmitter gated ion channels ( permeable to Na, K and Ca ions).
Binds to muscarinic, M1, M2 and M3, acetylcholine receptors which are G protein linked receptors.
Neurotransmitter of
Neuromuscular junction and preganglionic sympathetic and parasympathetic neurons.
Postganglionic parasympathetic neurons.
Somatic and visceral motor nuclei in the brainstem, basal nucleus of Meynert (degenerates in Alzheimer’s) and striatum ( degenerates in Huntington’s Disease).
Postganglionic sympathetic neurons innervating the eccrine sweat glands and blood vessels in skeletal muscles ( causes dilation).
Norepinephrine
Receptors are G protein linked receptors.
Neurotransmitter of postganglionic sympathetic neurons and locus ceruleus in midbrain and pons.
Metabolized by MAO and COMT to VMA ( vanillyl mandelic acid), NMN (normetanephrine) and MOPEG (phenylglycols).
Role in anxiety (↑), depression(↓), panic attacks and mania.
Epinephrine
Acts via G protein linked receptors.
Secreted by chromaffin cells of adrenal medulla.
Dopamine
Binds to D1 and D2 receptors which are G protein linked receptors.
Neurotransmitter in arcuate nucleus of the hypothalamus, ventral tegmental area and substantia nigra.
Decreased in Parkinson’s disease(↓) and increased in Schizophrenia(↑).
Serotonin ( 5 Hydroxytryptamine/ 5HT)
5HT1A,B,C,D,E,F receptors (↓camp) are G protein linked receptors found in CNS in the raphe nucleus of brainstem and hippocampus.
5 HT2A,B,C receptors (↑IP3 and DAG) are G protein linked receptors found in CNS.
5 HT3 receptor is a transmitter gated ion channel permeable to Na and K ions.
5 HT4.6.7 (↑camp) are also G protein linked receptors found in CNS
GABA (Gamma amino butyric acid)
GABA A receptor is a transmitter gated ion channel permeable to Cl ions.
GABA B is a G protein linked major inhibitory neurotransmitter in the CNS.
Glycine
Glycine receptor is a transmitter gated ion channel permeable to Cl ions.
It is major inhibitory neurotransmitter in the spinal cord.
Glutamate
Binds to N methyl D aspartate (NMDA) receptor, kainate or quisqualate receptors which are transmitter gated ion channels permeable to Na, K and Ca ions.
It is the major excitatory neurotransmitter of the CNS.
Opioids (endorphins and enkephalins ) and neuropeptides both use G protein linked receptors.