Abstracts - Association for Chemoreception Sciences

excite menthol- and/or CA-sensitive trigeminal primary sensory
neurons, using ratiometric calcium imaging of cultured trigeminal
ganglion (TG) and dorsal root ganglion (DRG) cells, and if they
modulate thermally-evoked responses of cold-sensitive secondorder
neurons in subnucleus caudalis (Vc) using in vivo singleunit
recordings in rats. Effects of cooling agents on TRPM8 or
TRPA1 were also investigated in cultured mammalian cells using
modified baculoviruses. Compound GIV1 robustly activated
TRPM8 (EC50 of ~400 nM) with some activation of TRPA1 at
much higher concentrations. GIV1 (100 µM) directly activated
7% of TG and 11% of DRG cells. Approximately 80% of cells
activated by GIV 1 were also activated by menthol compared to
only 23% for CA and 29% for capsaicin. Lingual application of
GIV 1 did not directly excite Vc neurons but significantly
enhanced their responses to cooling 20-min post-application and
briefly attenuated responses to noxious heat. GIV 2 appeared
selective for TRPM8 and excited 62% of menthol-sensitive Vc
neurons. Finally, in human sensory trials using toothpaste, GIV1
(0.16 mM) evoked a cooling sensation perceived as less intense but
of longer duration (90 min) than that evoked by GIV 2 (0.17 mM,
45 min). Moreover, GIV1 elicited a pungent sensation that was
perceived as stronger than that elicited by GIV 2. These novel
cooling compounds provide additional molecular tools to
investigate the neural processes of cold sensation.
Acknowledgements: NIH and Givaudan Flavors Corp.
#P97 POSTER SESSION II:
OLFACTORY PHYSIOLOGY & CELL BIOLOGY;
TASTE MOLECULAR GENETICS;
CHEMESTHESIS & TRIGEMINAL
Tingle sensation by a sanshool derivative and its effects on
primary sensory neurons
Amanda H. Klein 1 , Carolyn M. Sawyer 1 , Margaret A. Ivanov 1 ,
Susan Cheung 1 , Mirela Iodi Carstens 1 , Christopher T. Simons 2 ,
Jay Slack 2 , E. Carstens 1
1
University of California, Davis Davis, CA, USA,
2
Givaudan Flavors Corp., Cincinnati, OH, USA
Szechuan peppers are a preferred spice in some cuisines because of
their tingling-numbing and cooling sensations. The tingle agent
OH-a-sanshool activates a subset of sensory DRG neurons by
inhibiting 2-pore potassium channels. We presently investigated
the ability of a sanshool analog, isobutylalkenyl amide (IBA), to
elicit tingle sensation in humans and to excite primary sensory
neurons from rats. Using calcium imaging, IBA excited ~40% of
cultured rat dorsal root ganglion (DRG) neurons of different
sizes. Of IBA-sensitive cells, 30% also responded to menthol
and/or cinnamaldehyde (CA) and 66% to capsaicin (CAP), with
many responding to multiple TRP agonists. There was significant
self-desensitization to repeated application of IBA. CAP did not
cross-desensitize responses to IBA in CAP-insensitive DRG cells.
A modified time intensity procedure was used in human studies to
assess if lingual IBA (0.5%) evokes temporally distinct tingling,
pungent or cold sensations. IBA elicited a sensation initially
described as tingling and pungent, but after approximately 15 min,
as evoking a cooling sensation. Similarly, using a half-tongue, 2-
AFC methodology, pre-treatment with CAP (10 ppm) or mustard
oil (MO; 0.125%) did not cross-desensitize the tingle sensation
evoked by subsequent IBA application. The cellular responses
elicited by IBA are remarkably similar to the sensations observed
in human psychophysical trials. The ability of IBA to excite
menthol- and CAP-sensitive DRG cells is consistent with sensory
qualities (tingle, pungency, cool) elicited by IBA. The lack of
cross-desensitization by CAP or MO suggests that separate
populations of IBA-sensitive cells are likely involved in conveying
sensations of pungency and tingle. Acknowledgements: NIH
DE-013685, AR-057194
#P98 POSTER SESSION II:
OLFACTORY PHYSIOLOGY & CELL BIOLOGY;
TASTE MOLECULAR GENETICS;
CHEMESTHESIS & TRIGEMINAL
Ni 2+ -Ions directly activate transient receptor potential V1
Matthias Luebbert 1,2 , Debbie Radtke 1,2 , Hanns Hatt 1 ,
Christian H. Wetzel 1
1
Department of Cellular Physiology, Ruhr University Bochum
Bochum, Germany, 2 Ruhr University Research School Bochum,
Germany
TRPV1 is a member of the transient receptor potential (TRP)
family of cation channels. It is expressed in sensory neurons of
trigeminal and dorsal root ganglia, as well as in a wide range of
non-neuronal tissues including cells of the immune system.
As a polymodal receptor, TRPV1 can be activated by various
potentially harmful stimuli including divalent cations in
concentrations >10 mM. Searching for further activators and
modulators of TRPV1, we were interested in the effect of
Ni 2+ ions (NiSO4) known to induce allergic contact dermatitis.
Using whole-cell voltage-clamp recordings, we observed that
low millimolar doses of NiSO4 induced non-specific cationcurrents
in cultured capsaicin-sensitive trigeminal neurons of
mice. Furthermore NiSO4 led to an activation of recombinant rat
and human TRPV1 heterologously expressed in HEK293 and
CHO-cells. Usage of a voltage step protocol revealed a strong
outward rectification of these currents. Application of NiSO4 to
the cytoplasmic face of the membrane failed to induce any
currents. However, when delivered to the extracellular face of the
membrane NiSO4 induced an increase in the channels open
probability paralleled by a decrease in the channels conductance.
Both resulted in an increased net activity of TRPV1. In this
context we identified three amino acids localized in the channels
pore region, which are involved in the channels interaction with
Ni 2+ . When combined with other TRPV1 agonists, NiSO4
produces a bimodal effect on TRPV1 activity which depends on
the strength and concentration of the second stimulus. Outwardcurrents
induced by low doses of capsaicin, higher temperatures
(30°C – 40°C) and nearly neutral pH values (~pH = 7.0 – 6.5)
were augmented by low doses of NiSO4. In contrast, responses
to stronger stimuli were reduced by NiSO4.
P O S T E R S
Abstracts are printed as submitted by the author(s)
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