Brain circuits for food reward and food intake are different

Blocking a signalling hormone could stop over-eating.

A new study pinpoints the reward pathway in the brain that is targeted by a hunger hormone from the stomach; they show that the reward pathways engaged by this hormone for food reward are different to those involved in food intake. The study will be presented today [24 July 2013] as part of the 37th International Union of Physiological Sciences (IUPS) congress, in Birmingham.

Ghrelin – a hunger hormone produced by the empty stomach and secreted into the blood before mealtimes – is known to target the brain’s dopamine system, which is involved in reward. It is an important mechanism to ensure we seek out food for survival.

In this new study, the team administered ghrelin in the vicinity of the dopamine cells then used drugs to block dopamine signaling in rats to identify which exact pathway is important for ghrelin’s effects on food-motivated behaviour.

Professor Suzanne Dickson, University of Gothenburg Sweden, explains what they discovered:

“Our study identifies which dopamine pathway is targeted by ghrelin and that by suppressing this pathway, we can block ghrelin’s effects on food reward behaviour.  It further shows that this pathway may be important for food reward behaviour but not for food intake.”

Prof Dickson explains how this research can be applied to future therapies for over-eating disorders:

“Our research has implications for future therapeutic development for over-eating disorders that lead to obesity, for which the reward system (including the dopamine system) is strongly implicated; drugs that suppress dopamine signaling suppress the effects of ghrelin on food reward behaviour.”

Prof Dickson explains how they performed the research:

“The experimental approach investigates food motivation - how hard is a rat prepared to work (by pressing a lever) in order to obtain a sweet treat reward. Behaviour in this test is strongly linked to craving or reward-seeking.  Some rats will press a lever hundreds of times for a tiny sugar pellet. We show that this behaviour can be increased by ghrelin delivery to the dopamine cells in the midbrain, an effect blocked by drugs that interrupt dopamine signaling.”

Prof Dickson explains further research that needs to be carried out:

“We need to understand better the target systems in the brain for ghrelin, most of which are directly or indirectly linked to feeding control.  Given that this hormone strongly promotes food intake and food reward behavior, it will be important to discover new and specific ways to suppress its effects on these brain systems, with a view to finding new ways to tackle problematic over-eating, including food addictive behaviour.”

ENDS

 

Notes for Editors

1. Dr Dickson’s lecture at the IUPS Congress in Birmingham (ICC):

Ghrelin: an orexigenic gut - brain reward signal
Wednesday 24 July, 09.30 - 10.00, Hall 6 (The ICC)

As a part of the symposium: Peptide modulation of hedonic food intake

Wednesday 24 July, 0930 - 1130

2. Dr Dickson’s recently published paper:

Skibicka KP, Shirazi RH, Rabasa-Papio C, Alvarez-Crespo M, Neuber C, Vogel H, Dickson SL. (2013) Divergent circuitry underlying food reward and intake effects of ghrelin: Dopaminergic VTA-accumbens projection mediates ghrelin's effect on food reward but not food intake. Neuropharmacology, 73C:274-283. doi: 10.1016/j.neuropharm.2013.06.004. [Epub ahead of print]

3.Congress of the International Union of Physiological Sciences (IUPS), 22-26 July, Birmingham

The congress will bring together over 3000 physiologists from all corners of the globe to attend over 100 symposia and 30 keynote lectures. The congress has been running since 1889 and was started in an effort to promote physiology, encourage the interchange of ideas, and afford physiologists the opportunity to know one another personally. www.iups2013.org

 

Contacts

Speaker: Professor Suzanne Dickson, The Sahlgrenska Academy at the University of Gothenburg,

+46 31 786 3568; +46 703 693568, suzanne.dickson@gu.se

The Physiological Society (hosts of IUPS): Lucy Holmes, Media and Communications Officer

+44 (0)20 7269 5727; +44 (0)7917 610 731, pressoffice@physoc.org