Brain chemical with key role in substance abuse identified
August 26, 2005
New research performed in rats suggests that orexin, a brain chemical
involved in feeding behavior, arousal, and sleep, also plays a
role in reward function and drug-seeking behavior.
This study suggests that orexin may be a factor in modulating reward-seeking characteristic of substance abuse. The findings help to better identify neural pathways involved in drug abuse, craving and relapse, which may ultimately help scientists find more effective therapies.
This study is published online August 14, 2005 in the journal Nature.
The brain cells that secrete this substance, orexin, are in an area of the brain called the lateral hypothalamus, says Dr. Nora D. Volkow, director of the National Institute on Drug Abuse (NIDA), National Institutes of Health, which supported the study. This brain region has been implicated in reward function for many years, but no one was sure which brain chemicals, or neurotransmitters, were involved. For the first time, we now know exactly which substances are involved, which is a significant step forward in developing treatments.
The hypothalamus is a small area of the brain above and behind the roof of the mouth. It is involved with the involuntary nervous system and control of processes such as fluid maintenance, sugar balance, fat metabolism, regulation of body temperature, and control of hormonal secretion. The lateral hypothalamus is referred to as the brains hunger center.
We found that the more animals seek out cues associated with food or drug reward, the more activated these neurons become, says Dr. Harris. In rats that had their drug-seeking behavior extinguished, the preference for drug-associated cues was reinstated by chemically activating these cells and orexin production. These data suggest that this brain system may be involved in the development of drug craving that can perpetuate both addiction and relapse.
This neural system may be activated by environmental cues that cause addicts to relapse back to drug-taking behavior even after successfully going through rehabilitation and achieving abstinence, says Dr. Volkow.
The National Institute on Drug Abuse is a component of the National Institutes of Health, U.S. Department of Health and Human Services. NIDA supports most of the worlds research on the health aspects of drug abuse and addiction. The Institute carries out a large variety of programs to ensure the rapid dissemination of research information and its implementation in policy and practice. Fact sheets on the health effects of drugs of abuse and information on NIDA research and other activities can be found on the NIDA home page at http://www.drugabuse.gov/.
The National Institutes of Health (NIH) — The Nation's
Medical Research Agency — is comprised of 27 Institutes
and Centers and is a component of the U. S. Department of Health
and Human Services. It is the primary Federal agency for conducting
and supporting basic, clinical, and translational medical research,
and investigates the causes, treatments, and cures for both common
and rare diseases. For more information about NIH and its programs,
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