Abstract
Morphological study that searched to authenticate the presence of sinoaortic baroreceptor inputs within the dorsolateral medullary nucleus under electron microscopy analysis. After a 5-day survival period, 9 baroreceptor-denervated rats deeply anaesthetized with equithesin were transcardially perfused and their brains were histologically processed. The neuronal cytoarchitecture of the paratrigeminal nucleus comprehends afferent projections from other nuclei that have a distributive character regarding visceral and nociceptive functions in the cardiovascular reflex integration response. The medial portion of the nucleus receives afferent projections of the rostral ventrolateral medulla, as shown by retrograde neurotracing studies. The present results show that the medial extent of the paratrigeminal nucleus contains degenerated axoplasmic cellular components in sinoaortic deafferented rats. The number of degenerated axonal fibers was also larger in this area of the nucleus.
Highlights
The paratrigeminal nucleus (Pa5) cytoarchitecture is typified by a fusiform neuronal collection with distributive characteristics regarding visceral and nociceptive functions in the cardiovascular reflex integration response[1,2,3]
Within 2 to 4 days of postoperative period, electron microscopy analysis showed degenerated axon terminal fibers and identified synaptic elements in the medial extent of the paratrigeminal nucleus (Pa5, Figure 1), which projects to other nuclei functionally involved in central neuronal cardiovascular control
The bilateral cross-sections of the Pa5 revealed that the number of degenerated axonal fibers in the vicinity of synaptic elements were strictly distributed within the areas that receive afferent fibers from nucleus tractus solitarius (NTS) and RVL as described by Caous et al[2]
Summary
The paratrigeminal nucleus (Pa5) cytoarchitecture is typified by a fusiform neuronal collection with distributive characteristics regarding visceral and nociceptive functions in the cardiovascular reflex integration response[1,2,3]. The Pa5, a dorsal lateral medullary structure within the spinal trigeminal complex, has been studied with emphasis to morphological[4,5] and functional aspects. The latest participates in cardiovascular[6,7,8], respiratory[9,10] and thermoregulatory reflex mechanisms[11]. The Pa5 was primarily physiologically identified in rats by means of bradykinin microinjected into the dorsolateral medulla, which significantly increased the arterial blood pressure response[12]. The B2 bradykinin receptors were characterized and classified through autoradiography and gene expression. The principal density and distribution were einstein. 2012;10(2):145
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