Opioid modulation of taste hedonics
within the ventral striatum
by
Kelley AE, Bakshi VP, Haber SN,
Steininger TL, Will MJ, Zhang M.
Department of Psychiatry,
University of Wisconsin-Madison,
6001 Research Park Blvd.,
Madison, WI 53719, USA.
aekelley@facstaff.wisc.edu
Physiol Behav 2002 Jul;76(3):365-77

ABSTRACT

There is a long-standing interest in the role of endogenous opioid peptides in feeding behavior and, in particular, in the modulation of food reward and palatability. Since drugs such as heroin, morphine, alcohol, and cannabinoids, interact with this system, there may be important common neural substrates between food and drug reward with regard to the brain's opioid systems. In this paper, we review the proposed functional role of opioid neurotransmission and mu opiate receptors within the nucleus accumbens and surrounding ventral striatum. Opioid compounds, particularly those selective for the mu receptor, induce a potent increase in food intake, sucrose, salt, saccharin, and ethanol intake. We have explored this phenomenon with regard to macronutrient selection, regional specificity, role of output structures, Fos mapping, analysis of motivational state, and enkephalin gene expression. We hypothesize that opioid-mediated mechanisms within ventral striatal medium spiny neurons mediate the affective or hedonic response to food ('liking' or food 'pleasure'). A further refinement of this hypothesis is that activation of ventral striatal opioids specifically encodes positive affect induced by tasty and/or calorically dense foods (such as sugar and fat), and promotes behaviors associated with this enhanced palatability. It is proposed that this brain mechanism was beneficial in evolutionary development for ensuring the consumption of relatively scarce, high-energy food sources. However, in modern times, with unlimited supplies of high-calorie food, it has contributed to the present epidemic of obesity.

Desipramine
The nucleus accumbens
The dopamine transporter
Dopamine knock-out mice
Cannabis: humans are not rats
Adenosine and the nucleus accumbens
Depression, dopamine and dextroamphetamine
Mesolimbic medium spiny neurons and pleasure
Regulation of synapses in the nucleus accumbens
The magic millimeter? Locating the hedonic hotspot
Caffeine, dopamine/glutamate release in shell of NAc
GABA, opiates, happiness and the nucleus accumbens
Cooperative opioid and serotonergic mechanisms generate superior antidepressant effects

Refs
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