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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