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for various taste stimuli at 7 different timepoints from 0800 h to
2200 h using a stair-case methodology. Plasma leptin and insulin
were measured by an enzyme-linked immunosorbent assay. Blood
glucose levels were determined by the glucose dehydrogenase
method. In OW/Ob subjects with higher leptin levels (~20 ng/ml),
diurnal variation of mean recognition thresholds for sweet stimuli
(sugars and saccharin) became not evident. However, individual
differences in diurnal variation of leptin and recognition thresholds
for sweet and umami stimuli were negatively correlated with ratios
of postprandial blood glucose increase vs. insulin increase. Basal
leptin levels of OW/Ob subjects may already be higher than leptin’s
effective range on sweet taste modulation. Diurnal variation of
leptin levels and sweet and umami recognition thresholds may be
associated with overall efficacy of insulin on blood glucose among
OW/Ob individuals.
#P199
POSTER SESSION V:
TRIGEMINAL SYSTEM; BEHAVIOR
AND PSYCHOPHYSICS; ODORANT
RECEPTORS & OLFACTION PERIPHERY
Oxytocin decreases sensitivity to sweet taste
Michael S. Sinclair
1
, Marianne Abouyared
2,3
, Steven J. St. John
4
,
Nirupa Chaudhari
1,3
1
University of Miami, Program in Neurosciences Miami, FL, USA,
2
University of Miami, Medical Student-3 Miami, FL, USA,
3
University of Miami, Department of Physiology & Biophysics
Miami, FL, USA,
4
Rollins College, Department of Psychology
Winter Park, FL, USA
We have previously reported that oxytocin (OXT) elicits calcium
responses from taste cells and that oxytocin receptor is expressed in
glial-like taste cells (Sinclair et al, 2010). We asked if OXT alters
behavioral responses to sweet taste
in vivo
. We measured lick rates
of C57BL6/J mice (n = 21) in a Davis lickometer to a range of
sucrose concentrations (in M: 0, 0.03, 0.1, 0.2, 0.3, 0.6 1.0). The
naïve mice were exposed to sucrose once in the lickometer to
familiarize them with the novel taste. They were then tested twice,
injected 30 min. prior with either saline or OXT (0.1 mg/kg,
i.p.). Mice injected with saline for the first test were injected with
OXT for the second (n = 6) or vice versa (n = 15). OXT noticeably
reduced licking for low-to-intermediate concentrations of sucrose:
0.3 M (p<0.001; ANOVA) and 0.2 M (not-significant trend). OXT
slightly but significantly right-shifted the concentration-response
(EC50
saline
= 0.38 M, EC50
OXT
= 0.43 M, p<0.001), indicating a
decrease in sensitivity. Further, the Hill slope of the concentration
reponse curve is higher for OXT (1.8 vs. 2.2, p<0.05), also
indicative of a raised taste threshold. Male (n = 8) and female
(n = 7) did not differ in their response to sucrose, whether they
were injected with OXT or not. The dose of OXT injected (0.1
mg/kg i.p.) results in a plasma [OXT] of ~10 nM 30 min. after
injection. A 100-fold higher dose of OXT did not alter licking
responses to aversive stimuli (300 mM NaCl, 20 mM citric acid,
0.3 mM quinine). We previously reported that 10nM OXT evokes
calcium responses in taste cells (Sinclair et al, 2010). These results
suggest that OXT may modulate sweet taste sensitivity in behaving
mice by acting on glial-like cells in taste buds. Acknowledgements:
Supported by NIH / NIDCD grants R21DC010073 and
R01DC006021 to N.Chaudhari.
#P200
POSTER SESSION V:
TRIGEMINAL SYSTEM; BEHAVIOR
AND PSYCHOPHYSICS; ODORANT
RECEPTORS & OLFACTION PERIPHERY
Methodological Aspects of the Cold-Pressor Test and the
Analgesic Effect of Interoral Saccharin
Theresa L. White
1,2
, John Prescott
3
1
Le Moyne College Syracuse, NY, USA,
2
SUNY Upstate Medical
University Syracuse, NY, USA,
3
TasteMatters Research &
Consulting Sydney, Australia
An inter-oral bolus of sucrose has been shown to increase pain
tolerance in children, although this sweetness analgesia effect is
somewhat spurious in adults. A key question concerning sweetness
analgesia is whether its reward is mediated through the association
of sweetness with calories or the intrinsic value associated with the
palatability of sweet tastes. One way to address this question is to
investigate the phenomenon with an artificial sweetener, such as
saccharin. Although saccharin has been shown to increase pain
tolerance in rodents (Foo & Mason, 2009), it has not been well
investigated in human adults. Thirty participants were exposed to
four cold-pressor tests over two days and were asked in each test to
hold their hand in 4º C water for as long as they could tolerate the
pain while holding a tastant in their mouths. The tastants were
either water (presented each day) or a tastant [either .7M sucrose or
.005M saccharin] and were presented in a counterbalanced order.
After each test, participants rated pain intensity and tastant
qualities. When effects of testing order were taken into account,
sucrose did not show analgesic properties, but saccharin did,
t
(26)
= 2.01,
p
=0.05, and increased the amount of time that participants
held their hands in the cold water significantly more than sucrose,
t
(26) = 4.14,
p
<0.01. Despite the counterbalancing, presentation
order within a session strongly affected both sucrose,
t
(26) = -4.13,
p
<0.01, and saccharin,
t
(26) = 4.45,
p
<0.01, with the second
tastant in a session consistently resulting in greater pain
tolerance. This finding suggests that some of the spurious nature of
the sweetness analgesic effect may be due to subtle methodological
issues, such as the order of the stimuli. Acknowledgements:
This work was made possible through a grant from the Le Moyne
College Research and Development Committee
#P201
POSTER SESSION V:
TRIGEMINAL SYSTEM; BEHAVIOR
AND PSYCHOPHYSICS; ODORANT
RECEPTORS & OLFACTION PERIPHERY
The reduction of bitterness by sodium gluconate and the effects
of bitter receptor genotype in adults
Kristi M. Roberts, Laura D. Lukasewycz, Liang-Dar (Daniel)
Hwang, Sara M. Castor, Susana Finkbeiner, Loma B. Inamdar,
Robert F. Margolskee, Gary K. Beauchamp, Danielle R. Reed,
Julie A. Mennella
Monell Chemical Senses Center Philadelphia, PA, USA
The unpalatable flavor of a medicine can thwart the benefits of
even the most powerful of drugs and those individuals, both young
and old, who are genetically more sensitive to the bitterness may
experience the most difficulty in medication compliance. As part
of an ongoing study on the interaction between bitter blocking and
genetics in children and adults, we present here preliminary data on
ratings of the bitterness of urea, caffeine, quinine, propylthiouracil,
and denatonium benzoate (DB) with and without the addition of a
bitter blocker, sodium gluconate, in adults (N=64). Ratings were
made using the gLMS and subjects were genotyped for 58
94 | AChemS Abstracts 2012
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