Issn Print: 0195-9131
Publication Date: 2001/05/01
THE EFFECT OF ANTIDEPRESSANT TREATMENT AND ACTIVITY WHEEL RUNNING ON PREPRO-GALANIN MESSENGER RNA IN THE LOCUS COERULUS AFTER OLFACTORY BULBECTOMY
J D. Van Hoomissen; H A. O'Neal; P V. Holmes; R K. Dishman
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Author Information: University of Georgia, Athens, GA
Excerpt
Dysregulation of the central norepinephrine (NE) neuromodulatory system of the brain has been implicated in the etiology of depression and may provide a plausible model for examining the mechanism for the antidepressant effects of chronic exercise. In the present study, we examined messenger RNA (mRNA) for tyrosine hydroxylase (TH), the rate-limiting enzyme involved in NE synthesis, and prepor-galanin (GAL), a neuropeptide co-localized in 80% of the NE neurons, in the locus coerulus (LC). GAL mRNA has been increased after treadmill exercise training and after footshock among chronic activity wheel runners without a change in TH mRNA (O'Neal et al, MSSE 2000; Soares et al, Behav Neurosci, 1999). Olfactory bulbectomy (OBX), an animal model of depression, also has increased GAL mRNA without an effect on TH mRNA (Holmes et al, Mol Brain Res, 1996). The purpose of this study was to examine basal levels of these transcripts after chronic activity wheel running and compare the results to antidepressant drug treatment. Male Long-Evans rats were studied using a 2(OBX vs. sham) × 2(activity wheel running vs. sedentary) × 2(imipramine vs. saline) factorial design. In situ hybridization histochemistry with autoradiography was used to measure levels of TH and GAL mRNA after 21 days of treatment. No significant effects were observed for levels of TH mRNA. A significant increase in GAL mRNA occurred among imipramine treated animals (F(1, 62) = 5.18, p = 0.03, eta squared = 0.072) but there were no main effects of activity wheel running or OBX. The results indicate that basal levels of TH and GAL mRNA are not altered by activity wheel running. This might be partly explainable by the lower stress or intensity of voluntary activity wheel running compared to forced treadmill training or activity wheel runing combined with footshock.
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