Morphological changes in the sphenopalatine ganglion on the background of metabolic disorders in the experiment at rats

The sphenopalatine ganglion occupies a special place in neuropathology and dental neuropathy, accompanied by such pronounced symptoms as "vegetative storm". The aim of the research was obtaining information on the external structure of the sphenopalatine ganglion, the morphometric characteristics of its neurons in norm and in experimental diabetes. The study was carried out on male Wistar rats weighing 260-300 g: with a stereoscopic biological microscope, using ophthalmic instruments, we removed almost the entire gland that was not accompanied by significant bleeding under general anesthesia. Peculiarities of the external structure of the sphenopalatine ganglion of the white rat were studied by macro-micro preparations under a binocular microscope at 50 objects pervaded with silver nitrate, according to Christen-sen

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Sphenopalatine ganglion stimulation is a reversible and frequency-dependent modulator of the blood-brain barrier.

BACKGROUND: The sphenopalatine ganglion (SPG) is a vasoactive mediator of the anterior intracranial circulation in mammals. SPG stimulation has been demonstrated to alter blood-brain barrier (BBB) permeability, although this phenomenon is not well characterized. OBJECTIVE: To determine the effect of SPG stimulation on the BBB using rat models. METHODS: Extravasation of fluorescent tracer 70 kDa FITC-dextran into rat brain specimens was measured across a range of stimulation parameters to assess BBB permeability. Tight junction (TJ) morphology was compared by assessing differences in the staining of proteins occludin and ZO-1 and analyzing ultrastructural changes on transmission electron microscopy (TEM) between stimulated and unstimulated specimens. RESULTS: SPG stimulation at 10 Hz maximally increased BBB permeability, exhibiting a 6-fold increase in fluorescent traceruptake (1.66% vs 0.28%, p < 0.0001). This effect was reversed 4-hours after stimulation (0.36% uptake, p = 0.99). High-frequency stimulation at 20 Hz and 200 Hz did not increase tracer extravasation, (0.26% and 0.28% uptake, p = >0.999 and p = 0.998, respectively). Stimulation was associated a significant decrease in the colocalization of occludin and ZO-1 with endothelial markers in stimulated brains compared to control (74.6% vs. 39.7% and 67.2% vs. 60.4% colocalization, respectively, p < 0.0001), and ultrastructural changes in TJ morphology associated with increased BBB permeability were observed on TEM. CONCLUSION: This study is the first to show a reversible, frequency-dependent increase in BBB permeability with SPG stimulation and introduces a putative mechanism of action through TJ disruption. Bypassing the BBB with SPG stimulation could enable new paradigms in delivering therapeutics to the CNS. Further study of this technology is needed.

A Cadaveric Study of Ultrasound-Guided Maxillary Nerve Block Via the Pterygopalatine Fossa: A Novel Technique Using the Lateral Pterygoid Plate Approach.

BACKGROUND AND OBJECTIVES: This study aimed to describe and assess the accuracy and feasibility of a novel technique for ultrasound-guided maxillary nerve block using the lateral pterygoid plate (LPP) approach via the pterygopalatine fossa (PPF) in a soft cadaveric model. METHODS: Ten soft cadavers were studied. The curved array ultrasound transducer probe was applied over 1 side of the face of the cadavers in the open-mouth posture. It was placed transversely below the zygomatic arch for identifying the border of the maxillary tuberosity and the LPP. We tilted the curve probe from the caudal to the cranial direction until the uppermost part of the PPF was identified. The in-plane needle approach was used from the anterior-to-posterior and lateral-to-medial directions through the fossa, and 3 mL of methylene blue dye was injected. RESULTS: The spread of injectate after ultrasound-guided maxillary nerve block using the LPP approach was successfully performed in all cadavers as demonstrated by visualized moderate to marked traces of methylene blue within the PPF. No accidental injections in the maxillary arteries or facial nerves were observed. CONCLUSIONS: This cadaveric study suggests that ultrasound-guided maxillary nerve block using the LPP approach via the PPF has a high degree of accuracy and feasibility. Further studies are required to confirm its efficacy and safety for clinical application.