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Do Sedentary Conditions Affect the Number of C1 Neurons in Rat Rostral Ventrolateral Medulla?

Benjamin Huber, Patrick J. Mueller, Department of Physiology, Wayne State University School of Medicine, 540 E. Canfield, Detroit, MI 48201 Ida J. Llewellyn-Smith, Department of Cardiovascular Medicine, Human Physiology and Centre for Neuroscience, College of Medicine and Public Health, Flinders University, Bedford Park, South Australia, Australia

The rostral ventrolateral medulla (RVLM) is an important region in the brainstem for blood pressure control because it contains a critical subset of adrenergic (C1) neurons that project to sympathetic preganglionic neurons in the spinal cord. C1 neurons from sedentary rats show more dendritic branching than in physically active rats, suggesting a novel mechanism by which inactivity could increase sympathetic activity and contribute to hypertension. However, it is also possible that the absolute number of C1 neurons changes along with the number of dendritic branches in sedentary rats. Therefore, the purpose of this study was to test the hypothesis that there are more C1 neurons in the RVLM of rats living under sedentary conditions compared to freely exercising rats. Aiming to understand the mechanisms by which inactivity leads to hypertension, we maintained four-week old, male Sprague-Dawley rats for 10–12 weeks under either physically active conditions (running wheels; 410±5.6 km total per rat) or sedentary conditions (no running wheels). Following perfusion and post-fixation, sections of brainstem were first immunoperoxidase-stained black for phenylethanolamine N-methyltransferase (PNMT), a synthetic enzyme and marker of C1 neurons, and then brown for tyrosine hydroxylase (TH), the enzyme that all catecholamine neurons contain. PNMT+TH and TH only neurons in each rat were counted for the 6 sections containing the 600 μm caudal to the caudal pole of the facial nucleus (FN). Sedentary conditions did not produce a difference in the number, or rostrocaudal pattern, of TH+PNMT-immunoreactive C1 neurons compared to the active group, nor an interaction between the two (two way RM ANOVA, p>0.05 ea). Because the number of RVLM C1 neurons is the same in active and sedentary rats, an increase in the number of C1 neurons is not a cause of increased activation of vasomotor spinal neurons in sedentary rats.

(HL096787-09)




Additional Abstract Information

Presenter: Benjamin Huber

Institution: Wayne State University

Type: Oral

Subject: Exercise Science & Nutrition

Status: Approved


Time and Location

Session: Oral 2
Date/Time: Mon 3:00pm-4:00pm
Session Number: 223
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