Long-term effects of superior cervical ganglionectomy on cortical blood flow of non-anesthetized rabbits in resting and hypertensive conditions

The Role of the Superior Cervical Sympathetic Ganglion in Ischemia Reperfusion-Induced Acute Kidney Injury in Rats

Acute kidney injury (AKI) has been found to be a serious clinical problem with high morbidity and mortality, and is associated with acute inflammatory response and sympathetic activation that subsequently play an important role in the development of AKI. It is well known that the sympathetic nervous system (SNS) and immune system intensely interact and mutually control each other in order to maintain homeostasis in response to stress or injury. Evidence has shown that the superior cervical sympathetic ganglion (SCG) participates in the bidirectional network between the immune and the SNS, and that the superior cervical ganglionectomy has protective effect on myocardial infarction, however, the role of the SCG in the setting of renal ischemic reperfusion injury has not been studied. Here, we sought to determine whether or not the SCG modulates renal ischemic reperfusion (IR) injury in rats. Our results showed that bilateral superior cervical ganglionectomy (SCGx) 14 days before IR injury markedly reduced the norepinephrine (NE) in plasma, and down-regulated the increased expression of tyrosine hydroxylase (TH) in the kidney and hypothalamus. Sympathetic denervation by SCGx in the AKI group increased the level of blood urea nitrogen (BUN) and kidney injury molecule-1 (KIM-1), and exacerbated renal pathological damage. Sympathetic denervation by SCGx in the AKI group enhanced the expression of pro-inflammatory cytokines in plasma, kidney and hypothalamus, and increased levels of Bax in denervated rats with IR injury. In addition, the levels of purinergic receptors, P2X3R and P2X7R, in the spinal cord were up-regulated in the denervated rats of the IR group. In conclusion, these results demonstrate that the sympathetic denervation by SCGx aggravated IR-induced AKI in rats via enhancing the inflammatory response, thus, the activated purinergic signaling in the spinal cord might be the potential mechanism in the aggravated renal injury.

The cerebrovascular response to norepinephrine: A scoping systematic review of the animal and human literature

Intravenous norepinephrine (NE) is utilized commonly in critical care for cardiovascular support. NE's impact on cerebrovasculature is unclear and may carry important implications during states of critical neurological illness. The aim of the study was to perform a scoping review of the literature on the cerebrovascular/cerebral blood flow (CBF) effects of NE. A search of MEDLINE, BIOSIS, EMBASE, Global Health, SCOPUS, and Cochrane Library from inception to December 2019 was performed. All manuscripts pertaining to the administration of NE, in which the impact on CBF/cerebral vasculature was recorded, were included. We identified 62 animal studies and 26 human studies. Overall, there was a trend to a direct vasoconstriction effect of NE on the cerebral vasculature, with conflicting studies having demonstrated both increases and decreases in regional CBF (rCBF) or global CBF. Healthy animals and those undergoing cardiopulmonary resuscitation demonstrated a dose-dependent increase in CBF with NE administration. However, animal models and human patients with acquired brain injury had varied responses in CBF to NE administration. The animal models indicate an increase in cerebral vasoconstriction with NE administration through the alpha receptors in vessels. Global and rCBF during the injection of NE displays a wide variation depending on treatment and model/patient.

Sympathetic activities influence blood-flow velocity and resistance in the rabbit ophthalmic artery

PURPOSE

The aim of this study was to investigate sympathetic influences on blood-flow velocity and resistance in the rabbit ophthalmic artery during the transition period from the light to the dark phase.

METHODS

Eight (8) New Zealand albino rabbits were entrained to a daily 12-h light and 12-h dark cycle. Blood-flow velocities in the ophthalmic artery were determined at -2 (baseline), 0, 2, and 4 h after the onset of darkness. Pulsed and color Doppler images of the ophthalmic artery were recorded using a 12-MHz linear ultrasound transducer. Resistive index of blood flow was calculated using the peak systolic velocity and the end diastolic velocity. Measurements of intraocular pressure (IOP) were taken, using a pneumatonometer at the same time points. Blood-flow velocity, resistive index, and IOP were also determined in the same rabbits after surgical decentralization of the ocular sympathetic nerves.

RESULTS

Compared with the baseline at -2 h, a significant increase in the resistive index of blood flow in the ophthalmic artery occurred at 2 and 4 h after the onset of darkness. Parallel elevations of IOP were observed. After the sympathetic decentralization, peak systolic and end diastolic velocities decreased and resistive indexes increased from the presurgical values in the ophthalmic artery. In the postsurgical rabbits, elevation of IOP was absent during the light-dark transition period. There was also no time-dependent increase of resistive index in the ophthalmic artery.

CONCLUSIONS

During the light-dark transition period, resistance to blood flow in the rabbit ophthalmic artery increases in parallel to IOP elevation. The removal of sympathetic activities decreases blood-flow velocity, but increases blood-flow resistance. Like the endogenous elevation of IOP, the time-dependent increase of resistance to blood flow in the rabbit ophthalmic artery during the light-dark transition period depends upon, at least partially, ocular sympathetic activities.

Sympathectomy Causes Aggravated Lesions and Dedifferentiation in Large Rabbit Atherosclerotic Arteries without Involving Nitric Oxide

Previously [Histochem J 1997;29:279-286], we found that sympathectomy induced neointima formation in ear but not cerebral arteries of genetically hyperlipidemic rabbits. To clarify the influence of sympathetic nerves in atherosclerosis, and whether their influence involves vascular NO activity, we studied groups of normocholesterolemic intact (NI) and sympathectomized (NS), and hypercholesterolemic intact (HI) and sympathectomized (HS) rabbits (diet/6-hydroxydopamine for 79 days). Segments of basilar (BA) and femoral (FA) arteries were studied histochemically, to evaluate differentiation (anti-desmin, anti-vimentin, anti-h-caldesmon, and nuclear dye), by confocal microscopy, and by in vitro myography. In BAs, staining of NI and NS groups was similar. In hypercholesterolemic groups, a small neointima developed, more frequently in HS segments where smooth muscle cells (SMCs) positive for all antibodies appeared to be migrating into the neointima. In FAs, SMCs stained for the three antibodies in the NI group, but we observed desmin- and h-caldesmon-negative, vimentin-positive cells in some external medial layers of the NS, HI and HS groups, identical to adventitial fibroblasts. Large neointimas of the HS group contained vimentin-positive and largely desmin- and h-caldesmon-negative cells. Relaxation of BA or FA segments to acetylcholine was not decreased by sympathectomy. Sympathectomy increased the contraction of resting FAs to nitro-L-arginine (p = 0.0379). Thus, sympathectomy aggravates the tendency for FA SMCs to migrate and dedifferentiate, increasing atherosclerotic lesions, without decreasing NO activity, but has only minor effects on BAs.

The effect of unilateral sympathectomy and cavity preparation on peptidergic nerves and immune cells in rat dental pulp

Recent evidence suggests interactions between primary afferent nociceptors and postganglionic sympathetic efferents in the pathogenesis of inflammation. The effect of unilateral removal of the superior cervical ganglion on the innervation pattern of nerve fibers immunoreactive (IR) to calcitonin gene-related peptide (CGRP), substance P (SP), and neuropeptide Y (NPY), as well as the occurrence of immune cells in the injured and uninjured rat molar pulp, was investigated. Light microscopic immunocytochemistry demonstrated that the molar pulps contralateral to the sympathectomy contained a NPY-IR nerve fiber network more dense and heavily stained than unoperated control rats. The NPY-IR fibers showed, however, no sprouting after deep cavity preparation. There was no compensatory increase in CGRP- and SP-IR nerve fibers in the dental pulp after unilateral sympathectomy, although a significant increase in cells IR to CGRP and SP was found in the ipsilateral trigeminal ganglion. Unilateral sympathectomy induced a significant increase in immune cell density both in the inflamed and in the uninflamed dental pulp bilaterally. Our results demonstrate, for the first time, a trophic effect of the sympathetic nerves on immune cells in the dental pulp, indicating that an imbalance of sympathetic nerves may induce inflammation and pain in teeth.

Long-term superior cervical sympathectomy induces mast cell hyperplasia and increases histamine and serotonin content in the rat dura mater

Nerve fibres and mast cells are often described in close morphological and functional interactions in various organs such as the dura mater. The respective roles of mast cell activation and sympathetic impairment in cluster headache and migraine attacks have been repeatedly suggested. We have thus investigated the long-term effects of sympathectomy on mast cell morphology and content in the rat dura mater. Fifteen to 60 days after either sham, unilateral or bilateral superior cervical ganglionectomy, dura were removed for either histochemical or biochemical analysis. In the first case, they were fixed and mast cell heparin was stained by fluorescein isothiocyanate-conjugated avidin. Microscopic examination was followed by digital acquisitions using a tomographic process to assess mast cell density in the whole depth of the dura mater. Unilateral ganglionectomy induced a progressive and significant increase in mast cell density 15-60 days post-surgery in contralateral hemi-dura and 30 days post-surgery in ipsilateral hemi-dura. This increase was significant in both dura 60 days after bilateral ganglionectomy. Following perfusion with saline, we also examined the content of histamine and serotonin, pre-formed amines stored in mast cell granules. Biochemical analysis of dura serotonin and histamine content using high-pressure liquid chromatography and radioenzymatic assays, respectively, revealed under all conditions a serotonin tissue concentration lower than that of histamine. After sham ganglionectomy, the dura serotonin content increased from 15 to 60 days post-surgery, whereas the histamine content remained stable over the same period. After unilateral ganglionectomy, the histamine content increased progressively and significantly 30-60 days post-surgery in both hemi-dura, whereas the serotonin content became significantly different from that of sham only 60 days post-surgery in the ipsilateral dura. After bilateral ganglionectomy, the histamine level significantly increased in both hemi-dura 15-60 days post-surgery, whereas the serotonin level had significantly increased at 60 days post-surgery. These results clearly demonstrate, for the first time, a long-term trophic effect of sympathetic nerve degeneration on mast cells in the dura mater. Since mast cell activation has been described previously on the painful side of cluster headache patients during attack periods, we propose that the sympathetic impairment reported in these patients could be prominent, directly or indirectly inducing mast cell hyperplasia and changes in amine contents in the tissue concerned.

Subcutaneous tissue oxygen pressure: a reliable index of peripheral perfusion in humans after injury

The usual initial life-threatening effect of injury is hypovolemic shock. In the hierarchical physiologic response to hypovolemia, perfusion of peripheral tissues is sacrificed early and restored late. But the usual hemodynamic and metabolic measurements of blood pressure, urine output, and base deficit are not reliable indices of peripheral perfusion. Although the Clark electrode can quantitate tissue oxygen pressure and thereby serve as an index of perfusion, its use is compromised by several technical deficiencies. Recently, an optical method (optode) using fluorescent technology has been developed for measurement of oxygen tension in subcutaneous tissue (P sgO2). Our studies compared this device with the Clark electrode in the laboratory and tested its value in both animal and clinical studies of hypovolemic shock. The results of these several studies demonstrated that: (1) the new oximeter tracked a rapid fall or rapid rise of oxygen tension between room air (150 mm Hg) and 0 mm Hg ( a glucose oxidase/catalase solution) as well as the Clark electrode without encountering its technical problems; (2) with an acute hemorrhage to 20% of base line, the PsgO2 was found to decline rapidly in parallel with the decline of mean arterial pressure (MAP). Although the MAP rapidly returned to normal after immediate complete return of all shed blood, the PsgO2 did not reach normal levels for at least 2 hours, suggesting persistent peripheral vasoconstriction. (3) Studies in progress suggest that between 35 and 78% of trauma patients (n = 18) adequately resuscitated for hypovolemia b customary criteria have a decreased level of PsgO2 for as long as 60 hours after resuscitation for injury. If care is taken to prevent other causes of catecholamine induced vasoconstriction such as pain, fear, cold, and arterial hypoxia, these several results suggest that a certain number of injured patients are inadequately resuscitated despite the return to normal of conventional hemodynamic measurements. The serial analysis of PsgO2 may assist in managing patients and promote better understanding of the responses to injury.

Cerebral arterial innervation: II. Development of calcitonin-gene-related peptide and norepinephrine in the rat

The pre- and postnatal development of trigeminal calcitonin-gene-related peptide (CGRP)- and sympathetic norepinephrine (NE)-containing nerves supplying the cerebral arteries was studied with immunohistochemistry in rats. At 18-19 days in utero (E 18-19), CGRP fibers were present only as one or two longitudinal bundles zigzagging along the anterior cerebral artery and anterior communicating artery. Growth-cone-like swellings were found at the terminals of individual fibers. In contrast, at this same prenatal age NE fibers were present as a meshwork on all cerebral arteries. The density of NE fibers was higher in the rostral than in the caudal parts of the circle of Willis; growth cones were present on individual fibers at the middle segment of the basilar artery and distal parts of major cerebral arteries. At postnatal day 1-2 (PND 1-2; date of birth = PND 1), the outgrowth of CGRP axons extended along the walls of the middle cerebral and internal carotid arteries. These axons were relatively straight and unbranched. At the same time, NE fibers increased in number and density and continued to form the meshwork pattern on all cerebral arteries. At the end of the first postnatal week, all the longitudinal NE bundles on the rostral part of the circle of Willis began to form circular arborizations. At the end of the second postnatal week, the pattern of NE innervation had completely changed, consisting almost entirely of circumferential rather than tangential fibers. Beginning in the first postnatal week, CGRP fibers increased greatly in number and density and began to form a meshwork pattern. At the second postnatal week, the pattern of CGRP innervation, compared to the pattern at fetal and neonatal stages, had changed significantly, consisting predominantly of a meshwork pattern. By 4 weeks after birth, both the NE and CGRP fiber systems achieved adult densities and patterns. The present results demonstrate the following: 1) Both sympathetic-NE and trigeminal-CGRP innervation of cerebral arteries begin in utero; the NE system innervates corresponding parts of the vessels earlier than the CGRP system. 2) Both NE and CGRP fibers are more dense in the rostral than in the caudal segments of the circle of Willis; this rostrocaudal gradient is expressed in both density and pattern by the earliest fibers of both neurochemical systems and is maintained throughout all developmental stages.(ABSTRACT TRUNCATED AT 400 WORDS)

Ultrastructural evidence for a functional unit between nerve fibers and type II cerebral mast cells in the cerebral vascular wall

By histofluorescence microscopic examinations of pial arteries from rats and rabbits, we have observed that the routes of adrenergic fibers were apparently organized along successive sites of granular autofluorescent cells present in the adventitia. Subsequent electron microscopic studies showed that these cells were often situated in close apposition (80 to 200 nm) to the adventitial nerve bundles. The granular cells and nerve varicosities were frequently enclosed within the same basement membrane, with a membrane-to-membrane distance as small as 20 nm. However, no clear membrane differentiation was seen. These granular cells were identified histochemically by staining with Sudan Black, Oil Red O, Toluidine Blue, Alcian Blue, together with ultrastructural and pharmacological methods (48/80 compound and carbachol intracarotid infusions). The cells, many of which contained large amounts of lipids, showed morphological ultrastructural and pharmacological similarities to peripheral mast cells. Nerve bundles contained two types of varicosities: some of them degenerated after superior cervical ganglionectomy and were thus of sympathetic origin, whereas the others contained small clear vesicles (probably cholinergic) and/or large dense-cored vesicles (probably peptidergic). As we have shown that cholinomimetics induce exocytosis of these granular cells, the close relationship between these cells and the nerve fibers may indicate a neurogenic control of the cerebrovascular mast cell secretion. As these cells contain potent vasoactive substances, this relationship may be of importance in the genesis of physiological or pathological cerebrovascular events which are, as yet, poorly understood.

Assessment of perfusion in postoperative patients using tissue oxygen measurements

Subcutaneous tissue oxygen tension was measured as an index of perfusion in 44 postoperative patients. Hypoperfusion was defined as suboptimal tissue oxygen tension unresponsive to increased inspired oxygen but becoming responsive after increased fluid infusion. Twelve of thirty patients who underwent major abdominal and flank operations were found to be suboptimally perfused by this definition despite adequate fluid maintenance according to standard clinical criteria including urine output. Apparently, a significant number of postoperative abdominal surgery patients are not optimally perfused, and this state is not recognized by the present clinical criteria. Tissue oximetry may be a useful objective method of assessing tissue perfusion.