Renal Sensory Activity Regulates the γ-Aminobutyric Acidergic Inputs to the Paraventricular Nucleus of the Hypothalamus in Goldblatt Hypertension

Renal sensory activity is centrally integrated within brain nuclei involved in the control of cardiovascular function, suggesting that renal afferents regulate basal and reflex sympathetic vasomotor activity. Evidence has shown that renal deafferentation (DAx) evokes a hypotensive and sympathoinhibitory effect in experimental models of cardiovascular diseases; however, the underlying mechanisms involved in this phenomenon need to be clarified, especially those related to central aspects. We aimed to investigate the role of renal afferents in the control of γ-aminobutyric acid (GABA)ergic inputs to the paraventricular nucleus (PVN) of the hypothalamus in renovascular hypertensive (2K1C) rats and their influence in the regulation of cardiovascular function. Hypertension was induced by clipping the left renal artery. After 4 weeks, renal DAx was performed by exposing the left renal nerve to a 33 mM capsaicin solution for 15 min. After 2 weeks of DAx, microinjection of muscimol into the PVN was performed in order to evaluate the influence of GABAergic activity in the PVN and its contribution to the control of renal sympathetic nerve activity (rSNA) and blood pressure (BP). Muscimol microinjected into the PVN triggered a higher drop in BP and rSNA in the 2K1C rats and renal DAx mitigated these responses. These results suggest that renal afferents are involved in the GABAergic changes found in the PVN of 2K1C rats. Although the functional significance of this phenomenon needs to be clarified, it is reasonable to speculate that GABAergic alterations occur to mitigate microglia activation-induced sympathoexcitation in the PVN of 2K1C rats.

In Vitro and In Vivo Study of the Short-Term Vasomotor Response during Epileptic Seizures

Epilepsy remains one of the most common brain disorders, and the different types of epilepsy encompass a wide variety of physiological manifestations. Clinical and preclinical findings indicate that cerebral blood flow is usually focally increased at seizure onset, shortly after the beginning of ictal events. Nevertheless, many questions remain about the relationship between vasomotor changes in the epileptic foci and the epileptic behavior of neurons and astrocytes. To study this relationship, we performed a series of in vitro and in vivo experiments using the 4-aminopyridine model of epileptic seizures. It was found that in vitro pathological synchronization of neurons and the depolarization of astrocytes is accompanied by rapid short-term vasoconstriction, while in vivo vasodilation during the seizure prevails. We suggest that vasomotor activity during epileptic seizures is a correlate of the complex, self-sustained response that includes neuronal and astrocytic oscillations, and that underlies the clinical presentation of epilepsy.

Minireview: The involvement of renal afferents in the maintenance of cardiorenal diseases

Elevated sympathetic vasomotor activity is a common feature of cardiorenal diseases. Therefore, the sympathetic nervous system is an important therapeutic target, particularly the fibers innervating the kidneys. In fact, renal denervation has been applied clinically and shown promising results in patients with hypertension and chronic kidney disease. However, the underlying mechanisms involved in the cardiorenal protection induced by renal denervation have not yet been fully clarified. This mini-review highlights historical and recent aspects related to the role of renal sensory fibers in the control of cardiorenal function under normal conditions and in experimental models of cardiovascular disease. Results have demonstrated that alterations in renal sensory function participate in the maintenance of elevated sympathetic vasomotor activity and cardiorenal changes; as such, renal sensory fibers may be a potential therapeutic target for the treatment of cardiorenal diseases. Although it has not yet been applied in clinical practice, selective afferent renal denervation may be promising, since such an approach maintains efferent activity and can provide more refined control of renal function compared to total renal denervation. However more studies are needed to understand the mechanisms by which renal afferents partially contribute to such changes, in addition to the need to evaluate the safety and advantages of the approach for application in the clinical practice.

Role of spinal neurons in the maintenance of elevated sympathetic activity: a novel therapeutic target?

The control of sympathetic vasomotor activity involves a complex network within the brain and spinal circuits. An extensive range of studies has indicated that sympathoexcitation is a common feature in several cardiovascular diseases and that strategies to reduce sympathetic vasomotor overactivity in such conditions can be beneficial. In the present mini-review, we present evidence supporting the spinal cord as a potential therapeutic target to mitigate sympathetic vasomotor overactivity in cardiovascular diseases, focusing mainly on the actions of spinal angiotensin II on the control of sympathetic preganglionic neuronal activity.

Is it possible myogenic temporomandibular dysfunctions change the facial thermal imaging?

Infrared thermography is a functional examination that can document physiological changes such as abnormal cutaneous vasomotor activity in inflammatory and neurogenic pictures related to nociceptive and neuropathic pain by mapping the thermal distribution on the surface of the skin. Objective: The aim of this study was to verify if there is a facial thermal difference between the symptomatic and asymptomatic group for myogenic TMD according to the Research Diagnostic Criteria for Temporomandibular Disorder (RDC/TMD) in a European population sample. Material and methods: Sixty-one subjects between 20 and 40 years (26.2 ± 7.6 years) of both sexes were divided into two groups. The 28 facial thermo-anatomic points were selected and the values of minimum (Tmin), mean (Tmed) and maximum (Tmax) temperatures, average of hemiface temperatures of whole sample, temperature difference (ΔT(°C)) between groups and from these data an algorithm was formulated to separate the groups with greater accuracy. Results: There was an average difference of 0.3 °C of all points when comparing the two groups. The symptomatic group had lower maximum temperature for frontal and lateral views when compared to the asymptomatic group (p<0.05), and presented lower average temperature in frontal view (p<0.05). Symptomatic individuals for myogenic TMD presented a reduction of facial cutaneous blood flow corresponding to lower maximum temperature by the proposed method of analysis of thermal anatomical points. Conclusions: Infrared thermography showed potential to be a screening and complementary diagnostic examination method for patients with myogenic temporomandibular disorders in the daily clinic just by frontal face image.