TY - JOUR
T1 - Mechanisms of protease-activated receptor 2-evoked hyperexcitability of nociceptive neurons innervating the mouse colon
AU - Kayssi, Ahmed
AU - Amadesi, Silvia
AU - Bautista, Francisco
AU - Bunnett, Nigel
AU - Vanner, Stephen
PY - 2007
Y1 - 2007
N2 - Agonists of protease-activated receptor 2 (PAR2) evoke hyperexcitability of dorsal root ganglia
(DRG) neurons by unknown mechanisms. We examined the cellular mechanisms underlying
PAR2-evoked hyperexcitability of mouse colonic DRG neurons to determine their potential
role in pain syndromes such as visceral hyperalgesia. Colonic DRG neurons were identified
by injecting Fast Blue and DiI retrograde tracers into the mouse colon. Using immunofluorescence,
we found that DiI-labelled neurons contained PAR2 immunoreactivity, confirming
the presence of receptors on colonic neurons. Whole-cell current-clamp recordings of acutely
dissociated neurons demonstrated that PAR2 activation with a brief application (3 min) of PAR2
agonists, SLIGRL-NH2 and trypsin, evoked sustained depolarizations (up to 60 min) which
were associated with increased input resistance and a marked reduction in rheobase (50 at
30 min). In voltage clamp, SLIGRL-NH2 markedly suppressed delayed rectifier IK currents (55
at 10 min), but had no effect on the transient IA current or TTX-resistant Na+ currents. In
whole-cell current-clamp recordings, the sustained excitability evoked by PAR2 activation was
blocked by the PKC inhibitor, calphostin, and the ERK1/2 inhibitor PD98059. Studies of ERK1/2
phosphorylation using confocal microscopy demonstrated that SLIGRL-NH2 increased levels of
immunoreactive pERK1/2 in DRG neurons, particularly in proximity to the plasma membrane.
Thus, activation of PAR2 receptors on colonic nociceptive neurons causes sustained hyperexcitability
that is related, at least in part, to suppression of delayed rectifier IK currents. Both
PKC and ERK1/2 mediate the PAR2-induced hyperexcitability. These studies describe a novel
mechanism of sensitization of colonic nociceptive neurons that may be implicated in conditions
of visceral hyperalgesia such as irritable bowel syndrome.
AB - Agonists of protease-activated receptor 2 (PAR2) evoke hyperexcitability of dorsal root ganglia
(DRG) neurons by unknown mechanisms. We examined the cellular mechanisms underlying
PAR2-evoked hyperexcitability of mouse colonic DRG neurons to determine their potential
role in pain syndromes such as visceral hyperalgesia. Colonic DRG neurons were identified
by injecting Fast Blue and DiI retrograde tracers into the mouse colon. Using immunofluorescence,
we found that DiI-labelled neurons contained PAR2 immunoreactivity, confirming
the presence of receptors on colonic neurons. Whole-cell current-clamp recordings of acutely
dissociated neurons demonstrated that PAR2 activation with a brief application (3 min) of PAR2
agonists, SLIGRL-NH2 and trypsin, evoked sustained depolarizations (up to 60 min) which
were associated with increased input resistance and a marked reduction in rheobase (50 at
30 min). In voltage clamp, SLIGRL-NH2 markedly suppressed delayed rectifier IK currents (55
at 10 min), but had no effect on the transient IA current or TTX-resistant Na+ currents. In
whole-cell current-clamp recordings, the sustained excitability evoked by PAR2 activation was
blocked by the PKC inhibitor, calphostin, and the ERK1/2 inhibitor PD98059. Studies of ERK1/2
phosphorylation using confocal microscopy demonstrated that SLIGRL-NH2 increased levels of
immunoreactive pERK1/2 in DRG neurons, particularly in proximity to the plasma membrane.
Thus, activation of PAR2 receptors on colonic nociceptive neurons causes sustained hyperexcitability
that is related, at least in part, to suppression of delayed rectifier IK currents. Both
PKC and ERK1/2 mediate the PAR2-induced hyperexcitability. These studies describe a novel
mechanism of sensitization of colonic nociceptive neurons that may be implicated in conditions
of visceral hyperalgesia such as irritable bowel syndrome.
U2 - 10.1113/jphysiol.2006.126599
DO - 10.1113/jphysiol.2006.126599
M3 - Article
VL - 580
SP - 977
EP - 991
JO - The Journal of Physiology
JF - The Journal of Physiology
SN - 0022-3751
IS - 3
ER -