Dehydration Adaptation of the Adult Rat Modifies Brain Microtubule Electrical Activity of the Osmosensitive Supraoptic Nucleus

Brain microtubules (MTs) are important cytoskeletal structures in neurons that generate electrical oscillations in the frequency range of mammalian brain waves. However, the functional role of MT oscillations in the physiology of brain function remains unknown. Acute dehydration (DH) induced by water restriction results in changes in osmolality that require the modification of osmosensitive neuronal activity in the regions of the CNS involved in osmoregulation, in particular magnocellular neurons from the hypothalamic supraoptic nucleus (SON), responsible for the release of vasopressin and implicate osmosensor channels, associated with an intricate mesh of MTs. In the present study, we evaluated the effect of 24 h water deprivation (DH, dehydrated group) on the MT-based cytoskeleton of adult Wistar rats, as compared to a control group with free access to water (Control, euhydrated group). We obtained local field potentials (LFP) from isolated SON and cortex (CTX) brain tissue, observing spontaneous oscillations under both conditions. The electrical oscillations of the brain tissue from DH animals had different amplitudes and frequency peaks as compared to controls. A frequency domain spectral analysis of the time records indicated specific, SON-associated MT energy contributions of the frequency peaks in the challenged group, most particularly a dramatic increase in the 10-20 Hz range, and a statistically significant reduction in the high frequency 83-100 Hz region, not observed in the CTX samples. The data indicate that brain MTs respond to dehydration to produce electrical oscillations with distinct properties in the areas of the mammalian brain that specifically contribute to the homeostatic response. The present study provides the first evidence for a novel physiological mechanism associated with the electrical activity of the neuronal cytoskeleton and points to its possible involvement in the brain osmoregulatory mechanism.