Physiological and pathophysiological evaluation of baroreflex functionality with concurrent diffusion tensor imaging of its neural circuit in the rat

• Published in: Biomedical Journal 2019-12, Vol.42 (6), p.381-393
• Main Authors: Tsai, Ching-Yi, Wu, Jacqueline C C, Chen, Shu-Mi, Lin, Hsun-Hsun, Chan, Julie Y H, Chan, Samuel H H
• Format: Article
• Language: English
• Subjects: Animals; Anisotropy; Baroreceptors; Baroreflex - physiology; Blood pressure; Blood Pressure - physiology; Brain stem; Brain Stem - pathology; Brain Stem - physiology; Circuits; Diffusion; Diffusion Tensor Imaging - methods; Evaluation; Fourier transforms; Intoxication; Laboratory animals; Magnetic fields; Magnetic resonance imaging; Male; Mathematical analysis; Medulla oblongata; Nerve Net - pathology; Nerve Net - physiology; Neural networks; Neuroimaging; Neurons - physiology; Original article; Phenotypes; Physiology; Polyethylene; Rats, Sprague-Dawley; Recording sessions; Reflexes; Scanners; Sensory neurons; Solitary Nucleus - pathology; Solitary Nucleus - physiology; Solitary tract nucleus; Tensors; Veins & arteries; Water chemistry
• ISSN: 2319-4170; 2320-2890; 2320-2890
• DOI: 10.1016/j.bj.2019.10.006

By measuring the prevalence of neuronal traffic between two brain structures based on the notion that diffusion of water molecules along the axon in parallel bundles will create prominent anisotropy in the direction of the passage of action potentials, diffusion tensor imaging (DTI) may be taken as an effective tool for functional investigations. Demonstration of complementary results obtained from synchronized DTI of the baroreflex neural circuit and physiological or pathophysiological evaluation of baroreflex functionality should validate this notion. We implemented concurrent changes in neuronal traffic within the neural circuit of the baroreflex-mediated sympathetic vasomotor tone in the brain stem and alterations of its experimental surrogate under physiological and pathophysiological conditions. We further evaluated the functional and clinical implications of results obtained from this experimental paradigm in conjunction with baroreflex induction and a mevinphos intoxication model of brain stem death. We found that robust connectivity existed between the nucleus tractus solitarii and rostral ventrolateral medulla, the afferent and efferent nuclei of the baroreflex-mediated sympathetic vasomotor. Intriguingly, this connectivity was either reversibly disrupted or irreversibly severed to reflect alterations in baroreflex responses to physiological or pathophysiological challenges. The capability to observe simultaneous and complementary changes in neuronal traffic within the neural circuit of the baroreflex-mediated sympathetic vasomotor tone and alterations of its experimental surrogate that bears technical, scientific and clinical implications sustains the notion that coupled with relevant physiological phenotypes, DTI can be an effective investigative tool for functional evaluations of brain stem activities.