Deficiency of central dopamine in multiple obesity models
B.M. G
EIGER
, L.E. F
RANK
, A.D. C
ALDERA
-S
IU
,L.S
TILES
,
E.N. P
OTHOS
. Department of Pharmacology and
Experimental Therapeutics, Tufts University School of
Medicine, 136 Harrison Avenue, Boston, MA 02111, USA
The contribution of mesolimbic dopamine to the development
of dietary obesity is not yet well understood. Because this system
responds to feeding, dietary and/or genetic obesity could be linked
to central dopamine deficiencies. In this study, we use inbred
obesity-prone and obesity-resistant Sprague-Dawley adult female
rats (Charles River Laboratories) to show that obesity-
prone animals have lower basal extracellular dopamine levels
in the nucleus accumbens shell in vivo (0.02970.002 vs.
0.04070.001 pg/sample, po0.05). Using carbon fiber amperome-
try to monitor real-time-evoked dopamine release in all terminals
of the mesolimbic system, we find 50% lower dopamine signal
throughout in the obesity-prone rats. Leptin-deficient mice also
have low dopamine signal in nucleus accumbens slices, while lean
melanin concentrating hormone-deficient mice show the opposite.
Because these effects are potentially linked only to body weight
phenotype differences, we also studied inbred obesity-prone and
obesity-resistant rat neonates using immunocytochemistry and
quantitative PCR. As predicted from differences in stimulated
dopamine release in the adults, the number of VMAT2-
immunopositive sites (24871 vs. 64871; po0.01) and VMAT2
and TH mRNA levels (0.6270.03 vs. 1.6270.15; po0.01,
0.5270.15 vs. 1.0770.17; po0.05) were 50% lower in dopamine
neurons from obesity-prone pups. Since TH and VMAT2
essentially regulate dopamine quantal size, we conclude that
mesolimbic TH levels and VMAT2 transporter site number may
predict obesity predisposition in neonates. Furthermore, different
forms of obesity are linked to low levels of mesolimbic dopamine,
which the obese animal may attempt to overcome through excess
feeding. Supported by DK065872.
10.1016/j.appet.2007.03.075
Intraoral intake and c-Fos induction in rats with conditioned
flavor taste preferences
G.J. G
OLDEN
, T.A. H
OUPT
.
Department of Biological Sciences, Program in
Neuroscience, Florida State University, Tallahassee, FL,
USA
Conditioned flavor taste preferences (CFTP) are a robust form
of associative learning in which rats will choose a flavor (e.g. kool-
aid) previously mixed with a prefered taste (e.g. 8% fructose) over
a flavor previously mixed with a less prefered taste (e.g. 0.2%
saccharin). To explore the neural substrates of CFTP, we
examined c-Fos induction in response to intraoral infusions of
kool-aid/saccharin solutions in rats after acquisition of CFTP. In
order to minimize post-ingestive effects, kool-aid was paired with
two concentrations of saccharin, 0.2% ( highly preferred) and
0.05% sacccharin (isopreferred to water). To condition a CFTP,
adult male rats were given 24-h access to 2 bottles with kool-aid
mixed in either 0.2% saccharin (CS+/US+) or 0.05% saccharin
(CS-/US-); grape and cherry flavors were counterbalanced as
CS+ and CSÀ. After 8 days, CFTP was confirmed in a 24-h, 2-
bottle test of CS+/US- vs. CS-/US-. Rats were implanted with
intraoral catheters, and infused with 10 ml over 10 min of one of 4
solutions: CS+/US-, CS-/US-, US+, or US- (n=5–6/group).
Intake was measured by weighing rats before and after infusion.
One hour after infusion, rats were perfused and the brains
processed for c-Fos immunohistochemistry. Intraoral intakes of
the 2 kool-aid mixtures, CS+/US- (5.271.0 g) and CS-/US-
(5.171.1 g), and the 2 saccharin solutions, US+ (5.571.7 g) and
US- (3.271.1 g), were not different. Preliminary analysis of c-Fos
patterns revealed widespread activation of the rostral olfactory
and gustatory pathways, but greater activation within the
amygdala after CS+/US- infusion. Support: NIDCD 03198 and
00044.
10.1016/j.appet.2007.03.076
Effects of food supplements on feeding behavior and body weight
in rats
A. G
ONZALEZ
,A.L
O
´
PEZ
-
ESPINOZA
, A.G. M
ARTI
´
NEZ
,
V. A
GUILERA
,A.G
ALINDO
,C.
DE LA
T
ORRE
-I
BARRA
. Centro
de Estudios e Investigaciones en Comportamiento University
of Guadalajara, Me
´
xico, Me
´
xico
Twelve rats were divided in two groups, each one composed
with three females and three males. Water and food were available
during 4 h for both groups. The experimental phase, during the
first 2 h, the Group 1 was exposed to chow food, followed by 2 h
to food supplements in a solution diluted on 85 ml of water.
Group 2 was exposed to the same conditions but in an invested
sequence; rats in the first 2 h were exposed to food supplements
followed by chow food. We used food supplements with vanilla,
strawberry and chocolate flavor. Results showed that total food
intake was regulated by a process of food selection. Body weight
did not vary throughout the experiment.
10.1016/j.appet.2007.03.077
ARTICLE IN PRESS
Abstracts / Appetite 49 (2007) 272–341 293