Qin
Lab :
Noxious stimuli such as protons (H+), temperature (temp) etc.
applied to endorgans activate nociceptors. Injury leads to the
release of prostaglandins such as prostaglandin E2 (PGE2), serotonin
(5-HT), nerve growth factor (NGF) etc. from damaged cells, Bradykinin
(BK) from blood vessels and substance P (sP) from nociceptors.
These agents either activate nociceptors directly or senstitize
them to subsequent stimuli by parallel activation of intracellular
kinases by G-protein coupled receptors and tyrosine kinase receptors.
Primary nociceptive afferents (C-fibers, Ad-fibers) of dorsal
root ganglion (DRG) neurons synapse on second order neurons (S)
in the spinal dorsal horn (magnified in inset). Here, glutamate
(Glu) and sP released from primary afferent terminals (A) activate
glutamate receptors (NMDA R, AMPA R, mGluRs) and neurokinin-1
(NK-1) receptors, respectively, located post-synaptically on
spinal neurons. These synapses are negatively modulated by spinal
inhibitory interneurons (I), which employ enkephalins (Enk) or
gamma-amino-butyric acid (GABA) as neurotransmitters. Spinal
neurons convey nociceptive information to the brain and brainstem.
Activation of descending noradrenergic and/or serotonergic systems,
which originate in the brain and brainstem, leads to the activation
of spinal inhibitory interneurons (I) thereby resulting in antinociception.
(From http://encref.springer.de/mp/0002.htm)
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