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The Journal of Neuroscience, December 1, 2004, 24(48):10868-10877; doi:10.1523/JNEUROSCI.3223-04.2004
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Behavioral/Systems/Cognitive
Medial Hypothalamic 5-Hydroxytryptamine (5-HT)1A Receptors Regulate Neuroendocrine Responses to Stress and Exploratory Locomotor Activity: Application of Recombinant Adenovirus Containing 5-HT1A Sequences
Qian Li,1,2
Andrew Holmes,3
Li Ma,2
Louis D. Van de Kar,4
Francisca Garcia,4 and
Dennis L. Murphy2
1Department of Psychiatry and Behavioral Sciences, University of Texas Medical Branch, Galveston, Texas 77555-0431, 2Laboratory of Clinical Science, National Institute of Mental Health-National Institutes of Health (NIH), and 3Section on Behavioral Science and Genetics, National Institute on Alcohol Abuse and Alcoholism-NIH, Bethesda, Maryland 20892, and 4Department of Pharmacology, Loyola University Chicago, Maywood, Illinois 60153
Our previous studies found that serotonin transporter (SERT) knock-out mice showed increased sensitivity to minor stress and increased anxiety-like behavior but reduced locomotor activity. These mice also showed decreased density of 5-hydroxytryptamine (5-HT1A) receptors in the hypothalamus, amygdala, and dorsal raphe. To evaluate the contribution of hypothalamic 5-HT1A receptors to these phenotypes of SERT knock-out mice, two studies were conducted. Recombinant adenoviruses containing 5-HT1A sense and antisense sequences (Ad-1AP-sense and Ad-1AP-antisense) were used to manipulate 5-HT1A receptors in the hypothalamus. The expression of the 5-HT1A genes is controlled by the 5-HT1A promoter, so that they are only expressed in 5-HT1A receptor-containing cells. (1) Injection of Ad-1AP-sense into the hypothalamus of SERT knock-out mice restored 5-HT1A receptors in the medial hypothalamus; this effect was accompanied by elimination of the exaggerated adrenocorticotropin responses to a saline injection (minor stress) and reduced locomotor activity but not by a change in increased exploratory anxiety-like behavior. (2) To further confirm the observation in SERT-/- mice, Ad-1AP-antisense was injected into the hypothalamus of normal mice. The density and the function of 5-HT1A receptors in the medial hypothalamus were significantly reduced in Ad-1AP-antisense-treated mice. Compared with the control group (injected with Ad-track), Ad-1A-antisense-treated mice showed a significant reduction in locomotor activity, but again no changes in exploratory anxiety-like behaviors, tested by elevated plus-maze and open-field tests. Thus, the present results demonstrate that medial hypothalamic 5-HT1A receptors regulate stress responses and locomotor activity but may not regulate exploratory anxiety-like behaviors.
Key words: 5-HT1A promoter; ACTH; 125I-MPPI binding; elevated plus maze; open-field test; SERT knock-out
Received Aug 6, 2004;
revised October 17, 2004;
accepted October 18, 2004.
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