Roles of sympathetic nervous system in the suppression of cytotoxicity of splenic natural killer cells in the rat

Ageing and the Autonomic Nervous System

The vertebrate nervous system is divided into central (CNS) and peripheral (PNS) components. In turn, the PNS is divided into the autonomic (ANS) and enteric (ENS) nervous systems. Ageing implicates time-related changes to anatomy and physiology in reducing organismal fitness. In the case of the CNS, there exists substantial experimental evidence of the effects of age on individual neuronal and glial function. Although many such changes have yet to be experimentally observed in the PNS, there is considerable evidence of the role of ageing in the decline of ANS function over time. As such, this chapter will argue that the ANS constitutes a paradigm for the physiological consequences of ageing, as well as for their clinical implications.

Divergent splanchnic sympathetic efferent nerve pathways regulate interleukin-10 and tumour necrosis factor-α responses to endotoxaemia

The efferent branches of the splanchnic sympathetic nerves that enhance interleukin-10 (IL-10) and suppress tumour necrosis factor-α (TNF) levels in the reflex response to systemic immune challenge were investigated in anaesthetized, ventilated rats. Plasma levels of TNF and IL-10 were measured 90 min after intravenous lipopolysaccharide (LPS, 60 µg/kg). Splanchnic nerve section, ganglionic blockade with pentolinium tartrate or β₂ adrenoreceptor antagonism with ICI 118551 all blocked IL-10 responses. Restoring plasma adrenaline after splanchnic denervation rescued IL-10 responses. TNF responses were disinhibited by splanchnic denervation or pentolinium treatment, but not by ICI 118551. Splanchnic nerve branches were cut individually or in combination in vagotomized rats, ruling out any vagal influence on results. Distal splanchnic denervation, sparing the adrenal nerves, disinhibited TNF but did not reduce IL-10 responses. Selective adrenal denervation depressed IL-10 but did not disinhibit TNF responses. Selective denervation of either spleen or liver did not affect IL-10 or TNF responses, but combined splenic and adrenal denervation did so. Finally, combined section of the cervical and lumbar sympathetic nerves did not affect cytokine responses to LPS. Together, these results show that the endogenous anti-inflammatory reflex is mediated by sympathetic efferent fibres that run in the splanchnic, but not other sympathetic nerves, nor the vagus. Within the splanchnic nerves, divergent pathways control these two cytokine responses: neurally driven adrenaline, acting via β₂ adrenoreceptors, regulates IL-10, while TNF is restrained by sympathetic nerves to abdominal organs including the spleen, where non-β₂ adrenoreceptor mechanisms are dominant. KEY POINTS: An endogenous neural reflex, mediated by the splanchnic, but not other sympathetic nerves, moderates the cytokine response to systemic inflammatory challenge. This reflex suppresses the pro-inflammatory cytokine tumour necrosis factor-α (TNF), while enhancing levels of the anti-inflammatory cytokine interleukin-10 (IL-10). The reflex enhancement of IL-10 depends on the splanchnic nerve supply to the adrenal gland and on β₂ adrenoreceptors, consistent with mediation by circulating adrenaline. After splanchnic nerve section it can be rescued by restoring circulating adrenaline. The reflex suppression of TNF depends on splanchnic nerve branches that innervate abdominal tissues including, but not restricted to, spleen: it is not blocked by adrenal denervation or β₂ adrenoreceptor antagonism. Distinct sympathetic efferent pathways are thus responsible for pro- and anti-inflammatory cytokine components of the reflex regulating inflammation.

Reflex regulation of systemic inflammation by the autonomic nervous system

This short review focusses on the inflammatory reflex, which acts in negative feedback manner to moderate the inflammatory consequences of systemic microbial challenge. The historical development of the inflammatory reflex concept is reviewed, along with evidence that the endogenous reflex response to systemic inflammation is mediated by the splanchnic sympathetic nerves rather than by the vagi. We describe the coordinated nature of this reflex anti-inflammatory action: suppression of pro-inflammatory cytokines coupled with enhanced levels of the anti-inflammatory cytokine, interleukin 10. The limited information on the afferent and central pathways of the reflex is noted. We describe that the efferent anti-inflammatory action of the reflex is distributed among the abdominal viscera: several organs, including the spleen, can be removed without disabling the reflex. Understanding of the effector mechanism is incomplete, but it probably involves a very local action of neurally released noradrenaline on beta₂ adrenoceptors on the surface of tissue resident macrophages and other innate immune cells. Finally we speculate on the biological and clinical significance of the reflex, citing evidence of its power to influence the resolution of experimental bacteraemia.

Beta-Adrenergic Signaling in Tumor Immunology and Immunotherapy

Communication between the nervous and immune systems is required for the body to regulate physiological homeostasis. Beta-adrenergic receptors expressed on immune cells mediate the modulation of immune response by neural activity. Activation of beta-adrenergic signaling results in suppression of antitumor immune response and limits the efficacy of cancer immunotherapy. Beta-adrenergic signaling is also involved in regulation of hematopoietic reconstitution, which is critical to the graft-versus-tumor (GVT) effect and to graft-versus-host disease (GVHD) following allogeneic hematopoietic cell transplantation (HCT). In this review, the function of beta-adrenergic signaling in mediating tumor immunosuppression will be highlighted. We will also discuss the implication of targeting beta-adrenergic signaling to improve the efficacy of cancer immunotherapy including the GVT effect, and to diminish the adverse effects including GVHD.

Mechanistic Links Between Obesity, Diabetes, and Blood Pressure: Role of Perivascular Adipose Tissue

Obesity is increasingly prevalent and is associated with substantial cardiovascular risk. Adipose tissue distribution and morphology play a key role in determining the degree of adverse effects, and a key factor in the disease process appears to be the inflammatory cell population in adipose tissue. Healthy adipose tissue secretes a number of vasoactive adipokines and anti-inflammatory cytokines, and changes to this secretory profile will contribute to pathogenesis in obesity. In this review, we discuss the links between adipokine dysregulation and the development of hypertension and diabetes and explore the potential for manipulating adipose tissue morphology and its immune cell population to improve cardiovascular health in obesity.

Emerging Roles of Sympathetic Nerves and Inflammation in Perivascular Adipose Tissue

Perivascular adipose tissue (PVAT) is no longer recognised as simply a structural support for the vasculature, and we now know that PVAT releases vasoactive factors which modulate vascular function. Since the discovery of this function in 1991, PVAT research is rapidly growing and the importance of PVAT function in disease is becoming increasingly clear. Obesity is associated with a plethora of vascular conditions; therefore, the study of adipocytes and their effects on the vasculature is vital. PVAT contains an adrenergic system including nerves, adrenoceptors and transporters. In obesity, the autonomic nervous system is dysfunctional; therefore, sympathetic innervation of PVAT may be the key mechanistic link between increased adiposity and vascular disease. In addition, not all obese people develop vascular disease, but a common feature amongst those that do appears to be the inflammatory cell population in PVAT. This review will discuss what is known about sympathetic innervation of PVAT, and the links between nerve activation and inflammation in obesity. In addition, we will examine the therapeutic potential of exercise in sympathetic stimulation of adipose tissue.

Anti-inflammatory reflex action of splanchnic sympathetic nerves is distributed across abdominal organs

The splanchnic anti-inflammatory pathway has been proposed as the efferent arm of the inflammatory reflex. Although much evidence points to the spleen as the principal target organ where sympathetic nerves inhibit immune function, a systematic study to locate the target organ(s) of the splanchnic anti-inflammatory pathway has not yet been made. In anesthetized rats made endotoxemic with lipopolysaccharide (LPS, 60 µg/kg iv), plasma levels of tumor necrosis factor-α (TNF-α) were measured in animals with cut (SplancX) or sham-cut (Sham) splanchnic nerves. We confirm here that disengagement of the splanchnic anti-inflammatory pathway in SplancX rats (17.01 ± 0.95 ng/ml, mean ± SE) strongly enhances LPS-induced plasma TNF-α levels compared with Sham rats (3.76 ± 0.95 ng/ml). In paired experiments, the responses of SplancX and Sham animals were compared after the single or combined removal of organs innervated by the splanchnic nerves. Removal of target organ(s) where the splanchnic nerves inhibit systemic inflammation should abolish any difference in LPS-induced plasma TNF-α levels between Sham and SplancX rats. Any secondary effects of extirpating organs should apply to both groups. Surprisingly, removal of the spleen and/or the adrenal glands did not prevent the reflex splanchnic anti-inflammatory action nor did the following removals: spleen + adrenals + intestine; spleen + intestine + stomach and pancreas; or spleen + intestine + stomach and pancreas + liver. Only when spleen, adrenals, intestine, stomach, pancreas, and liver were all removed did the difference between SplancX and Sham animals disappear. We conclude that the reflex anti-inflammatory action of the splanchnic nerves is distributed widely across abdominal organs.

Nerve Stimulation: Immunomodulation and Control of Inflammation

Neuronal stimulation is an emerging field in modern medicine to control organ function and re-establish physiological homeostasis during illness. Transdermal nerve stimulation with electroacupuncture is currently endorsed by the World Health Organization (WHO) and the National Institutes of Health (NIH), and is used by millions of people to control pain and inflammation. Recent advances in electroacupuncture may permit activation of specific neuronal networks to prevent organ damage in inflammatory and infectious disorders. Experimental studies of nerve stimulation are also providing new information on the functional organization of the nervous system to control inflammation and its clinical implications in infectious and inflammatory disorders. These studies may allow the design of novel non-invasive techniques for nerve stimulation to help to control immune and organ functions.

Anti-stress effect of the Lactobacillus pentosus strain S-PT84 in mice

We investigated if the orally administered Lactobacillus pentosus strain S-PT84 (S-PT84) might show anti-stress activity and ameliorate stress-induced immune suppression in mice. Stress of mice induced an increase in serum corticosterone and a decrease in splenic natural killer activity and in the number of splenocytes versus control mice. However, these changes were not observed in stressed mice that had been administered S-PT84. Furthermore, interleukin (IL)-12 and IL-10 production, which was downregulated in lipopolysaccharide-activated macrophages from stressed mice, was maintained at control levels in the macrophages of stressed mice that had been fed S-PT84. Interferon-γ production, which was downregulated in concanavalin A-activated splenocytes from stressed mice, tended to be maintained at control levels in stressed mice that had been fed S-PT84, although IL-4 production by these cells was not influenced by S-PT84 administration. Additionally, reduced glutathione (GSH) levels were decreased in serum and peritoneal macrophages from stressed mice versus controls, but these GSH levels were significantly higher in stressed animals that had been administered S-PT84 compared with those that had not. These results suggest that S-PT84 exerts anti-stress activity through immune modulation and/or antioxidative activity.

Baroreflex activation in conscious rats modulates the joint inflammatory response via sympathetic function

The baroreflex is a critical physiological mechanism controlling cardiovascular function by modulating both the sympathetic and parasympathetic activities. Here, we report that electrical activation of the baroreflex attenuates joint inflammation in experimental arthritis induced by the administration of zymosan into the femorotibial cavity. Baroreflex activation combined with lumbar sympathectomy, adrenalectomy, celiac subdiaphragmatic vagotomy or splenectomy dissected the mechanisms involved in the inflammatory modulation, highlighting the role played by sympathetic inhibition in the attenuation of joint inflammation. From the immunological standpoint, baroreflex activation attenuates neutrophil migration and the synovial levels of inflammatory cytokines including TNF, IL-1β and IL-6, but does not affect the levels of the anti-inflammatory cytokine IL-10. The anti-inflammatory effects of the baroreflex system are not mediated by IL-10, the vagus nerve, adrenal glands or the spleen, but by the inhibition of the sympathetic drive to the knee. These results reveal a novel physiological neuronal network controlling peripheral local inflammation.

Autonomic nervous system and immune system interactions

The present review assesses the current state of literature defining integrative autonomic-immune physiological processing, focusing on studies that have employed electrophysiological, pharmacological, molecular biological, and central nervous system experimental approaches. Central autonomic neural networks are informed of peripheral immune status via numerous communicating pathways, including neural and non-neural. Cytokines and other immune factors affect the level of activity and responsivity of discharges in sympathetic and parasympathetic nerves innervating diverse targets. Multiple levels of the neuraxis contribute to cytokine-induced changes in efferent parasympathetic and sympathetic nerve outflows, leading to modulation of peripheral immune responses. The functionality of local sympathoimmune interactions depends on the microenvironment created by diverse signaling mechanisms involving integration between sympathetic nervous system neurotransmitters and neuromodulators; specific adrenergic receptors; and the presence or absence of immune cells, cytokines, and bacteria. Functional mechanisms contributing to the cholinergic anti-inflammatory pathway likely involve novel cholinergic-adrenergic interactions at peripheral sites, including autonomic ganglion and lymphoid targets. Immune cells express adrenergic and nicotinic receptors. Neurotransmitters released by sympathetic and parasympathetic nerve endings bind to their respective receptors located on the surface of immune cells and initiate immune-modulatory responses. Both sympathetic and parasympathetic arms of the autonomic nervous system are instrumental in orchestrating neuroimmune processes, although additional studies are required to understand dynamic and complex adrenergic-cholinergic interactions. Further understanding of regulatory mechanisms linking the sympathetic nervous, parasympathetic nervous, and immune systems is critical for understanding relationships between chronic disease development and immune-associated changes in autonomic nervous system function.

Reflex control of inflammation by the splanchnic anti-inflammatory pathway is sustained and independent of anesthesia

Following an immune challenge, there is two-way communication between the nervous and immune systems. It is proposed that a neural reflex--the inflammatory reflex--regulates the plasma levels of the key proinflammatory cytokine TNF-α, and that its efferent pathway is in the splanchnic sympathetic nerves. The evidence for this reflex is based on experiments on anesthetized animals, but anesthesia itself suppresses inflammation, confounding interpretation. Here, we show that previous section of the splanchnic nerves strongly enhances the levels of plasma TNF-α in conscious rats 90 min after they received intravenous LPS (60 μg/kg). The same reflex mechanism, therefore, applies in conscious as in anesthetized animals. In anesthetized rats, we then determined the longer-term effects of splanchnic nerve section on responses to LPS (60 μg/kg iv). We confirmed that prior splanchnic nerve section enhanced the early (90 min) peak in plasma TNF-α and found that it reduced the 90-min peak of the anti-inflammatory cytokine IL-10; both subsequently fell to low levels in all animals. Splanchnic nerve section also enhanced the delayed rise in two key proinflammatory cytokines IL-6 and interferon γ. That enhancement was undiminished after 6 h, when other measured cytokines had subsided. Finally, LPS treatment caused hypotensive shock in rats with cut splanchnic nerves but not in sham-operated animals. These findings demonstrate that reflex activation of the splanchnic anti-inflammatory pathway has a powerful and sustained restraining influence on inflammatory processes.

Effect of anaesthetic technique on the natural killer cell anti-tumour activity of serum from women undergoing breast cancer surgery: a pilot study

BACKGROUND

Animal models and retrospective clinical data suggest that certain anaesthetic techniques can attenuate immunosuppression and minimize metastasis after cancer surgery. Natural killer (NK) T cells are a critical component of the anti-tumour immune response. We investigated the effect of serum from women undergoing primary breast cancer surgery, randomized to propofol-paravertebral block (PPA) or sevoflurane-opioid (GA) anaesthetic techniques, on healthy human donor NK cell function and cytotoxicity against oestrogen and progesterone receptor-positive breast cancer cells (HCC1500).

METHODS

Ten subjects who donated serum before operation and 24 h after operation in an ongoing randomized prospective trial (NCT 00418457) were randomly selected. Serum from PPA (n=5) and GA (n=5) subjects was co-cultured with HCC1500 and healthy primary NK cells. NK cell activating receptors (NKp30, NKp44, NKp46, 2b4, CD16, NKG2D), cytokine production, NK CD107a expression, and cytotoxicity towards HCC1500 were examined.

RESULTS

Serum from PPA subjects did not alter normal NK marker expression or secretion of cytokines. Serum from GA subjects reduced NK cell activating receptor CD16 [from mean (sem), 82 (2)% to 50 (4)%, P=0.001], IL-10 [from 1700 (80) to 1200 (92) pg ml(-1), P=0.001], and IL-1β [from 68 (12) to 19 (4) pg ml(-1), P=0.01]. An increase in NK cell CD107a [23 (2)% to 37(3)%, P=0.007] and apoptosis of HCC1500 [11 (1)% to 21 (2)%, P=0.0001] was observed with PPA serum, but not GA serum, treated NK cells.

CONCLUSION

Serum from women with breast cancer undergoing surgical excision who were randomized to receive a PPA anaesthetic technique led to greater human donor NK cell cytotoxicity in vitro compared with serum from women who received GA.

CLINICAL TRIAL REGISTRATION

NCT 041857.

The effect of the sympathetic nervous system on splenic natural killer cell activity in mice administered the Lactobacillus pentosus strain S-PT84

Splenic sympathetic nerve activity (SNA) modulates cellular immune functions such as splenic natural killer cell activity. Lactobacillus pentosus strain S-PT84 enhances splenic natural killer cell activity. Here, we examined whether S-PT84 affects splenic natural killer activity through splenic SNA in BALB/c mice. Splenic SNA was significantly decreased following the administration of S-PT84. This phenomenon was inhibited by pretreatment with thioperamide (histamine H₃ receptor antagonist), suggesting that S-PT84 directly affected splenic SNA. Thioperamide also inhibited the increase in splenic natural killer activity by S-PT84. Thus, the change in splenic natural killer activity by S-PT84 may be partially modulated through SNA.

Autonomic regulation of cellular immune function

The nervous system and the immune system (IS) are two integrative systems that work together to detect threats and provide host defense, and to maintain/restore homeostasis. Cross-talk between the nervous system and the IS is vital for health and well-being. One of the major neural pathways responsible for regulating host defense against injury and foreign antigens and pathogens is the sympathetic nervous system (SNS). Stimulation of adrenergic receptors (ARs) on immune cells regulates immune cell development, survival, proliferative capacity, circulation, trafficking for immune surveillance and recruitment, and directs the cell surface expression of molecules and cytokine production important for cell-to-cell interactions necessary for a coordinated immune response. Finally, AR stimulation of effector immune cells regulates the activational state of immune cells and modulates their functional capacity. This review focuses on our current understanding of the role of the SNS in regulating host defense and immune homeostasis. SNS regulation of IS functioning is a critical link to the development and exacerbation of chronic immune-mediated diseases. However, there are many mechanisms that need to be further unraveled in order to develop sound treatment strategies that act on neural-immune interaction to resolve or prevent chronic inflammatory diseases, and to improve health and quality of life.

Sympathetic nervous system and inflammation: a conceptual view

The peripheral sympathetic nervous system is organized into function-specific pathways that transmit the activity from the central nervous system to its target tissues. The transmission of the impulse activity in the sympathetic ganglia and to the effector tissues is target cell specific and guarantees that the centrally generated command is faithfully transmitted. This is the neurobiological basis of autonomic regulations in which the sympathetic nervous system is involved. Each sympathetic pathway is connected to distinct central circuits in the spinal cord, lower and upper brain stem and hypothalamus. In addition to its conventional functions, the sympathetic nervous system is involved in protection of body tissues against challenges arising from the environment as well as from within the body. This function includes the modulation of inflammation, nociceptors and above all the immune system. Primary and secondary lymphoid organs are innervated by sympathetic postganglionic neurons and processes in the immune tissue are modulated by activity in these sympathetic neurons via adrenoceptors in the membranes of the immune cells (see Bellinger and Lorton, 2014). Are the primary and secondary lymphoid organs innervated by a functionally specific sympathetic pathway that is responsible for the modulation of the functioning of the immune tissue by the brain? Or is this modulation of immune functions a general function of the sympathetic nervous system independent of its specific functions? Which central circuits are involved in the neural regulation of the immune system in the context of neural regulation of body protection? What is the function of the sympatho-adrenal system, involving epinephrine, in the modulation of immune functions?

Reflex control of inflammation by sympathetic nerves, not the vagus

We investigated a neural reflex that controls the strength of inflammatory responses to immune challenge - the inflammatory reflex. In anaesthetized rats challenged with intravenous lipopolysaccharide (LPS, 60 μg kg(-1)), we found strong increases in plasma levels of the key inflammatory mediator tumour necrosis factor α (TNFα) 90 min later. Those levels were unaffected by previous bilateral cervical vagotomy, but were enhanced approximately 5-fold if the greater splanchnic sympathetic nerves had been cut. Sham surgery had no effect, and plasma corticosterone levels were unaffected by nerve sections, so could not explain this result. Electrophysiological recordings demonstrated that efferent neural activity in the splanchnic nerve and its splenic branch was strongly increased by LPS treatment. Splenic nerve activity was dependent on inputs from the splanchnic nerves: vagotomy had no effect on the activity in either nerve. Together, these data demonstrate that immune challenge with this dose of LPS activates a neural reflex that is powerful enough to cause an 80% suppression of the acute systemic inflammatory response. The efferent arm of this reflex is in the splanchnic sympathetic nerves, not the vagi as previously proposed. As with other physiological responses to immune challenge, the afferent pathway is presumptively humoral: the present data show that vagal afferents play no measurable part. Because inflammation sits at the gateway to immune responses, this reflex could play an important role in immune function as well as inflammatory diseases.

Differential control of efferent sympathetic activity revisited

This article reviews 40 years of research (1970-2010) into the capability of the efferent sympathetic nervous system to display differential responsiveness. Discovered first were antagonistic changes of activity in sympathetic filaments innervating functionally different sections of the cardiovascular system in response to thermal stimulation. During the subsequent four decades of investigation, a multitude of differential sympathetic efferent response patterns were identified, ranging from opposing activity changes at the level of multi-fiber filaments innervating different organs to the level of single fibers controlling functionally different structures in the same organ. Differential sympathetic responsiveness was shown to be displayed in response to exogenous or artificial stimulation of afferent sensory fibers transmitting particular exogenous stimuli, especially those activating peripheral nociceptors. Moreover, sympathetic differentiation was found to be characteristic of autonomic responses to environmental changes by which homeostasis in the broadest sense would be challenged. Heat or cold loads or their experimental equivalents, altered composition of inspired air or changes in blood gas composition, imbalances of body fluid control, and exposure to agents challenging the immune system were shown to elicit differential efferent sympathetic response patterns which often displayed a high degree of specificity. In summary, autonomic adjustments to changes of biometeorological parameters may be considered as representative of the capability of the sympathetic nervous system to exert highly specific efferent control of organ functions by which bodily homeostasis is maintained.

Cholinergic control of inflammation

Cytokine production is necessary to protect against pathogens and promote tissue repair, but excessive cytokine release can lead to systemic inflammation, organ failure and death. Inflammatory responses are finely regulated to effectively guard from noxious stimuli. The central nervous system interacts dynamically with the immune system to modulate inflammation through humoral and neural pathways. The effect of glucocorticoids and other humoral mediators on inflammatory responses has been studied extensively in the past decades. In contrast, neural control of inflammation has only been recently described. We summarize autonomic regulation of local and systemic inflammation through the 'cholinergic anti-inflammatory pathway', a mechanism consisting of the vagus nerve and its major neurotransmitter, acetylcholine, a process dependent on the nicotinic acetylcholine receptor alpha7 subunit. We recapitulate additional sources of acetylcholine and their contribution to the inflammatory response, as well as acetylcholine regulation by acetylcholinesterase as a means to attenuate inflammation. We discuss potential therapeutic applications to treat diseases characterized by acute or chronic inflammation, including autoimmune diseases, and propose future research directions.

Blockade of adrenoreceptors inhibits the splenic response to stroke

Recent studies have highlighted the involvement of the peripheral immune system in delayed cellular degeneration after stroke. In the permanent middle cerebral artery occlusion (MCAO) model of stroke, the spleen decreases in size. This reduction occurs through the release of splenic immune cells. Systemic treatment with human umbilical cord blood cells (HUCBC) 24 h post-stroke blocks the reduction in spleen size while significantly reducing infarct volume. Splenectomy 2 weeks prior to MCAO also reduces infarct volume, further demonstrating the detrimental role of this organ in stroke-induced neurodegeneration. Activation of the sympathetic nervous system after MCAO results in elevated catecholamine levels both at the level of the spleen, through direct splenic innervation, and throughout the systemic circulation upon release from the adrenal medulla. These catecholamines bind to splenic alpha and beta adrenoreceptors. This study examines whether catecholamines regulate the splenic response to stroke. Male Sprague-Dawley rats either underwent splenic denervation 2 weeks prior to MCAO or received injections of carvedilol, a pan adrenergic receptor blocker, prazosin, an alpha1 receptor blocker, or propranolol, a beta receptor blocker. Denervation was confirmed by reduced splenic expression of tyrosine hydroxylase. Denervation prior to MCAO did not alter infarct volume or spleen size. Propranolol treatment also had no effects on these outcomes. Treatment with either prazosin or carvedilol prevented the reduction in spleen size, yet only carvedilol significantly reduced infarct volume (p < 0.05). These results demonstrate that circulating blood borne catecholamines regulate the splenic response to stroke through the activation of both alpha and beta adrenergic receptors.

Cytokine-induced suppression of medial preoptic neurons: mechanisms and neuroimmunomodulatory effects

We have shown that the medial preoptic area (MPO) in the hypothalamus is a major site where interferon (IFN)-alpha acts to induce suppression of splenic natural killer (NK) cell activity through an activation of sympathetic nervous system (SNS) in rats. Here, we discuss the hypothalamic mechanisms of the cytokine action using in vivo and in vitro preparations in rats. Lesion of the MPO activated the SNS and suppressed splenic NK cell activity in anesthetized rats, suggesting that the MPO had an inhibitory influence on nerve activity. Since both IFN-alpha and interleukin (IL)-1beta are known to suppress MPO neuron activity, it is suggested that the suppression/loss of the MPO caused by cytokine actions/lesions disinhibits the hypothalamic-sympathetic pathway, thereby resulting in an increase in the splenic SNS and reduction of NK activity. To explore the cellular mechanisms of the suppression of MPO neurons, the effects of Prostaglandin E2 (PGE2), one of the major mediators of cytokine action in the brain, on the glutamate-induced membrane currents were examined using the perforated patch-clamp method in mechanically dissociated MPO neurons. Patch-clamp analysis revealed that PGE2 potentiated the Ca2+-dependent K+ current (KCa) stimulated by Ca2+ entry through N-methyl-D-aspartate channels. We suggest that the cytokine-induced decrease in the firing rates of MPO neurons may be a result of an increase in interspike intervals caused by PGE(2)-induced enhancement of KCa in the presence of glutamatergic inputs.

Effect of the culture extract of Lentinus edodes mycelia on splenic sympathetic activity and cancer cell proliferation

The spleen is an important organ for tumor immunity, and the splenic sympathetic nerve has a suppressive effect on splenic natural killer (NK) cytotoxicity. On the basis of this and reports that Lentinus edodes (Shiitake mushroom) has tumor-inhibitory effects, the authors hypothesized that an extract of a mycelial culture of L. edodes grown in a solid medium of sugar-cane bagasse and defatted rice bran-L.E.M-might affect the sympathetic splenic sympathetic nerve activity (Splenic-SNA) and thus inhibit tumor proliferation. Thus, the effect of L.E.M on Splenic-SNA and human cancer cell proliferation was examined. Splenic-SNA was found to be suppressed by an intraduodenal L.E.M injection in urethane-anesthetized rats, which significantly inhibited increases in the tumor volume of human colon and breast cancer cells implanted in athymic nude mice. These findings suggest that L.E.M has an inhibitory effect on tumor proliferation possibly via a reduction in NK cytotoxicity through the suppression of Splenic-SNA.

Splenic nerve is required for cholinergic antiinflammatory pathway control of TNF in endotoxemia

The autonomic nervous system maintains homeostasis through its sympathetic and parasympathetic divisions. During infection, cells of the immune system release cytokines and other mediators that cause fever, hypotension, and tissue injury. Although the effect of cytokines on the nervous system has been known for decades, only recently has it become evident that the autonomic nervous system, in turn, regulates cytokine production through neural pathways. We have previously shown that efferent vagus nerve signals regulate cytokine production through the nicotinic acetylcholine receptor subunit alpha7, a mechanism termed "the cholinergic antiinflammatory pathway." Here, we show that vagus nerve stimulation during endotoxemia specifically attenuates TNF production by spleen macrophages in the red pulp and the marginal zone. Administration of nicotine, a pharmacological agonist of alpha7, attenuated TNF immunoreactivity in these specific macrophage subpopulations. Synaptophysin-positive nerve endings were observed in close apposition to red pulp macrophages, but they do not express choline acetyltransferase or vesicular acetylcholine transporter. Surgical ablation of the splenic nerve and catecholamine depletion by reserpine indicate that these nerves are catecholaminergic and are required for functional inhibition of TNF production by vagus nerve stimulation. Thus, the cholinergic antiinflammatory pathway regulates TNF production in discrete macrophage populations via two serially connected neurons: one preganglionic, originating in the dorsal motor nucleus of the vagus nerve, and the second postganglionic, originating in the celiac-superior mesenteric plexus, and projecting in the splenic nerve.

Brain cytokines and the 5-HT system during poly I:C-induced fatigue

Fatigue is evoked not only by peripheral factors, such as muscle fatigue, but also by the central nervous system (CNS). For example, it is generally known that the feeling of fatigue is greatly influenced by psychological aspects, such as motivation. However, little is known about the central mechanisms of fatigue. The clinical symptoms of chronic fatigue syndrome (CFS) are shown to include disorders in neuroendocrine, autonomic, and immune systems. On the other hand, it has been demonstrated that cytokines produced in the brain play significant roles in neural-immune interactions through their various central actions, including hypothalamo-pituitary and sympathetic activation, as well as immunosuppression. In this article, using the immunologically induced fatigue model, which was achieved by intraperitoneal (i.p.) injection of synthetic double-stranded RNAs, polyriboinosinic: polyribocytidylic acid (poly I:C) in rats, we show an involvement of brain interferon-alpha (IFN-alpha) and serotonin (5-HT) transporter (5-HTT) in the central mechanisms of fatigue. In the poly I:C-induced fatigue rats, expression of IFN-alpha and 5-HTT increased, while extracellular concentration of 5-HT in the medial prefrontal cortex decreased, probably on account of the enhanced expression of 5-HTT. Since the poly I:C-induced reduction of the running wheel activity was attenuated by a 5-HT(1A) receptor agonist, but not by 5-HT(2), 5-HT(3), or dopamine D(3) receptor agonists, it is suggested that the decrease in 5-HT actions on 5-HT(1A) receptors may at least partly contribute to the poly I:C-induced fatigue.

Enhanced expression of brain interferon-alpha and serotonin transporter in immunologically induced fatigue in rats

Immunologically induced fatigue was induced in rats by intraperitoneal injection of a synthetic double-stranded RNA, polyriboinosinic : polyribocytidylic acid (poly I:C). An injection of poly I:C (3 mg/kg) decreased the daily amounts of spontaneous running wheel activity to approximately 60% of the preinjection level until day 8. Quantitative analysis of mRNA levels demonstrated that interferon-alpha (IFN-alpha) and p38 mitogen-activated protein kinase mRNAs increased in the medial preoptic, paraventricular and ventromedial hypothalamic nuclei and in cortex on both days 1 and 8, while interleukin-1beta and an inhibitor of nuclear factor kappaB (IkappaB)-beta mRNAs increased on day 1, but recovered within a week. Serotonin transporter (5-HTT) mRNA also increased on days 1 and 8 after poly I:C injection in the same brain regions where IFN-alpha mRNA increased. The increased 5-HTT had a functional significance, because in vivo brain microdialysis revealed that an i.p. injection of poly I:C induced a decrease in the extracellular concentration of 5-HT in the prefrontal cortex; the decrease was blocked by local perfusion with a nonselective 5-HT reuptake inhibitor, imipramine. Finally, the poly I:C-induced fatigue was attenuated by a 5-HT1A receptor agonist but not by 5-HT2, 5-HT3 or dopamine D3 agonists. These findings, taken together, suggest that disorders in brain IFN-alpha and 5-HTT expression may be involved in the neuronal mechanisms of the poly I:C-induced fatigue.

Chronic electric stimulation of the midbrain ventral tegmental area increases spleen but not blood natural killer cell cytotoxicity in rats

Previously we found that in conscious, freely behaving rats chronic electric stimulation of the lateral hypothalamus (LH) caused significant augmentation of natural killer cell cytotoxicity (NKCC) and a large granular lymphocyte (LGL) number more pronounced in the spleen than in the peripheral blood. The LH belongs to the so-called "brain reward system", a collection of the central structures whose activation produce positive emotions. The midbrain ventral tegmental area (VTA) is another prominent reward-relevant structure. In the present work, chronic electric stimulation of VTA (constant current 0.1 ms duration cathodal pulses delivered at frequency 50 Hz during 60 min daily session for 14 consecutive days) caused in rats an increase in the spleen but not in the peripheral blood NKCC (chromium release assay) without simultaneous effect on the number of large granular lymphocytes (LGL) (morphological method) and plasma level of prolactin (PRL), growth hormone (GH), corticosterone (COR), and testosterone (TST). This effect was anatomically specific as no influence of analogous thalamic stimulation on immune and endocrine response was found. The results obtained indicate that both reward-related areas VTA and LH enhance the cell-mediated immune response, represented by natural killer cytotoxicity, especially in the spleen. However, the effect pronounced by VTA is weaker than that of LH, possibly due to additional connections of LH with the hormonal and/or autonomic control systems.

Blood and spleen natural killer cell cytotoxicity after exposure to open field stress in rats: the effect of spontaneous locomotor activity

In the present study we compared the effects of acute (30 min), white and illuminated open field (OF) stress on behavioral, immune and endocrine variables between rats divided into high (HR) and low (LR) responsive to novelty and in a non-divided group. It was found that OF-induced behavioral depression which was in parallel to suppression of both blood and spleen natural killer cell cytotoxicity (NKCC), large granular lymphocyte (LGL) and lymphocyte numbers occurred in stressed LR rats only. There was no significant difference in the plasma level of corticosterone (COR) and testosterone (TST) between HR and LR rats. In contrast, when the HR and LR groups were examined together (the non-divided group), no significant influence of OF stress on behavioral activity or NKCC was observed. These results emphasize that individual differences as measured by spontaneous locomotor activity play the important role for the study of the mechanisms involved in stress-induced immunomodulation and indicate that OF stress-induced behavioral depression in low reactivity animals may be accompanied by impaired defence against viral infections and neoplastic growth, which is functionally related to NKCC.

Prolonged effects of polyriboinosinic:polyribocytidylic acid on spontaneous running wheel activity and brain interferon-alpha mRNA in rats: a model for immunologically induced fatigue

Following 2 weeks acclimation to the running wheel in the home cages, an i.p. injection of a synthetic double-stranded RNA, polyriboinosinic:polyribocytidylic acid (poly I:C, 3 mg/kg), was performed to produce the immunologically induced fatigue in rats. The daily amounts of spontaneous running wheel activity decreased to about 40-60% of the preinjection level until day 9 with normal circadian rhythm, then gradually returned to the baseline level by day 14. Rats given a heat exposure (36 degrees C for 1 h) for the consecutive 3 days showed an increase in activity except for the first day. In the open field test, the total moving distance and the number of rearing of the poly I:C-injected rats decreased on day 1, but they were not different from the saline-injected group on day 7, suggesting that the poly I:C-induced fatigue on day 7 was not due to the peripheral problems such as muscle/joint pain, but involved the CNS. Quantitative analysis of mRNA levels using a real-time capillary reverse transcriptase-polymerase chain reaction (RT-PCR) method revealed that interferon-alpha (IFN-alpha) mRNA contents in the cortex, hippocampus, hypothalamic medial preoptic, paraventricular, and ventromedial nuclei were higher in the poly I:C group than those in the saline and heat-exposed groups on day 7, although the amount of interleukin-1 beta mRNA showed no differences. Serum adrenocorticotropic hormone and catecholamine levels were not significantly different between groups. The present results indicate that the prolonged fatigue induced by poly I:C, which is evaluated by the spontaneous running wheel activity, can be used as an animal model for the immunologically induced fatigue associated with viral infection, and suggest that brain IFN-alpha may play a role in this model.

The effects of lateral hypothalamic lesions on peripheral blood natural killer cell cytotoxicity in rats hyper- and hyporesponsive to novelty

Individual variability in the central control of the cellular immune responses is the main subject of the study. Previously, it was found that destruction of the lateral hypothalamus (LH) produced long-term depression of the cytotoxicity of NK cells (NKCC) and their number (LGL). In the present experiment we compared changes in the peripheral blood NKCC, LGL number, as well as leukocyte and lymphocyte number, their mitogenic activity and plasma corticosterone level evoked by electrolytic LH lesions in rats which were categorized as either high (HR) and low (LR) responders according to their locomotor response to a new environment. It was found that: (1) before the lesion NKCC (measured by 51Cr release assay) was higher in the HRs than in LRs; (2) LH damage caused a drop in NKCC and LGL number (21st postlesion day) preceded by a transient enhancement (5th postlesion day) significant for HRs only. As a result of a greater decrease in the HRs than LRs the baseline differences between groups disappeared by 21st postlesion day; (3) NKCC and LGL depression was not accompanied by changes in lytic activity of a single NK cell (agarose assay) which indicates that NKCC decrease concerned the population level and was dependent on LGL redistribution and/or recycling rate; (4) on the 21st postlesion day there was a significant leuko- and lymphopenia in the lesioned groups both HRs and LRs; (5) proliferative lymphocyte response to PWM (colorimetric assay) and plasma corticosterone level were not affected either by the motility level or by the lesion. The results emphasize the importance of individual differences in behavioral reactivity for NKCC regulation and a possible involvement of LH in the mechanism which connects high locomotor activity with stimulation of NKCC.

Somatosympathetic reflexes from the low back in the anesthetized cat

In the appendicular skeleton, substantial evidence demonstrates that somatosensory input from deep tissues including limb muscles and joints elicits somatosympathetic reflexes. Much less is known about the presence and organization of these reflexes from the axial skeleton. We determined if mechanical loading of the lumbar spine and lumbar paraspinal muscle irritation reflexively affects postganglionic sympathetic nerve discharge (SND) to the spleen and kidney. In 27 alpha-chloralose-anesthetized cats, the L2-4 multifidus muscles were injected with the inflammatory irritant mustard oil (20%, 60 microl total) and a vertebral load (100% body weight) was applied dorsal-ventral at the L3 spinous process. Mustard oil injection alone without vertebral loading (n = 7) increased mean splenic SND (60%), renal SND (30%), and heart rate (HR; 52 bpm). Mustard oil injection accompanied by the vertebral load (n = 7) increased mean splenic SND (55%), renal SND (16%), and HR (27 bpm). Blood pressure changes were biphasic and could not account for these changes. When the vertebral load accompanied mustard oil, the increases in splenic SND, renal SND, and HR remained elevated in a pattern significantly different from when the vertebral load was absent. Vehicle injection combined with the mechanical load (n = 3) did not change any of the autonomic responses. Similarly, mustard oil injection combined with a mechanical load did not change these responses when either the medial branches of the dorsal rami from T11-L5 had been cut (n = 4) or when the spinal cord had been transected between the second and third cervical vertebrae (n = 6). The results indicate that inflammatory stimulation of multifidus muscle in the low back evokes a somatosympathetic reflex integrated supraspinally in the upper cervical spinal cord or higher. The reflex's afferent arm travels in the medial branch of the dorsal ramus, and its efferent arm can affect sympathetic outflow to the spleen and the kidney as well as HR and BP. A static mechanical load applied to the lumbar spine accompanying the inflammatory stimulus appears to sustain the inflammatory-induced reflex activity.

The role of the sympathetic nervous system in moxibustion-induced immunomodulation in rats

The effects of chemical sympathectomy on moxibustion-induced changes in splenic natural killer (NK) cell cytotoxicity, T and B cell proliferation were studied. Direct moxibustion was applied to the unilateral Zusanli region. NK cell cytotoxicity was suppressed by moxibustion in both vehicle-treated rats and sympathectomized rats. T cell proliferation was not affected by moxibustion. B cell proliferation showed no significant change in vehicle-treated rats, but an increase was seen in sympathectomized rats treated with moxibustion. Sympathectomy alone induced an augmentation of NK cell cytotoxicity and a suppression of T cell proliferation. These results suggest that the sympathetic nervous system (SNS) has no significant role in the mechanism of moxibustion-induced immunomodulation.

Change in mitochondrial membrane potential in peripheral blood lymphocytes, especially in natural killer cells, is a possible marker for surgical stress on the immune system

There is accumulating evidence that surgical stresses cause impairment of systemic immune responses, which may promote susceptibility to infection as well as growth of remnant cancer cells in cancer patients. Although alterations in numbers, populations, and functions of lymphocytes have been extensively studied to assess modulation of the immune system, the precise mechanisms of immunosuppression caused by surgical stresses have not been identified, nor have methods been developed to estimate the magnitude of surgical stresses on the immune system. In the present study, to evaluate the effects of surgical procedures on the immune system, the mitochondrial membrane potential (Delta Psi(m)) of peripheral blood lymphocytes (PBL) from 25 patients who underwent various types of operation was measured by flow cytometry using 3,3'-dihexiloxacarbocyanine iodide (DiOC(6)(3)) on the day before operation and on postoperative day (POD) 1, POD 3, and POD 7. The Delta Psi(m) in PBL, especially in natural killer (NK) cell population, was reduced after major surgery. In particular, the reduction of Psi Delta(m) in NK cells appeared to be proportional to the severity of the surgical procedures and reflected the impairment of cellular function. Interestingly, the Delta Psi(m) in NK cells was also negatively correlated with the level of plasma noradrenaline after major surgery, suggesting that the reduction of Delta Psi(m) in NK cells induced by surgical stresses may be mediated, at least in part, by the accompanying increase in plasma noradrenaline. Monitoring of Delta Psi(m) in PBL after operation may be one of the useful markers for estimating the magnitude of surgical stresses on the immune system.

Effects of hemispheric lateralization and site specificity on immune alterations induced by kindled temporal lobe seizures

The effects of kindled seizures elicited from sites in the left and right temporal lobes on mitogen-induced proliferation (LPS, Con A, PHA) and induction of representative TH1 (IFN-gamma) and TH2 (IL-10, IL-4) cytokines were determined in activated rat splenocytes. With reference to cell proliferation, the changes depended on the hemispheric side and location of kindling. Kindling of the left side mediated significant increase in cell proliferation by LPS. Left side kindling resulted in decreased cell proliferation by PHA. Although right side kindling showed no change when taken together, further analysis showed that the reduced proliferation by PHA was mediated when the pyriform cortex was kindled with no change from amygdaloid nuclei. Similar hemispheric polarization was observed in the production of IL-10 and IFN-gamma by Con A-stimulated splenocytes in left side kindled rats. Hence, kindled temporal lobe seizures induced changes in specific immune functions. These effects are not only lateralized but are also specific with respect to the particular region kindled. Since epileptic patients have altered immune functions, this report contributes to our understanding of this complex immune-brain cross-talk in epilepsy.

Immunosuppression induced by central action of morphine is not blocked by mifepristone (RU 486)

Morphine causes immunosuppression by binding to opioid receptors on immune cells, or indirectly by acting on receptors in the brain. However, morphine exact mechanism of action has not been elucidated. In the present study, we investigated the role of glucocorticoids in morphine-mediated immunosuppression after acute action in the rat mesencephalon periaqueductal gray (PAG). Natural killer (NK) cell activity and T cell proliferation were used to evaluate potential indirect mechanisms of morphine action. Microinjection of morphine in the ventral-caudal aspect of the PAG significantly (p < 0.01) suppressed splenic NK cell cytotoxic activity (32% reduction), and antiTCR-, IL-2-, antiTCR + IL-2, and Con A-induced thymic (30% to 50% reduction) and splenic (35% to 70% reduction) lymphocyte proliferation compared with PAG-injected saline control animals. The glucocorticoid receptor antagonist mifepristone (RU 486) did not block the immunosuppressive effects of morphine, suggesting that such effects are independent of activation of the hypothalamic-pituitary-adrenal axis.

Modulation of beta-adrenergic receptor subtype activities in perioperative medicine: mechanisms and sites of action

This review focuses on the mechanisms and sites of action underlying beta-adrenergic antagonism in perioperative medicine. A large body of knowledge has recently emerged from basic and clinical research concerning the mechanisms of the life-saving effects of beta-adrenergic antagonists (beta-AAs) in high-risk cardiac patients. This article re-emphasizes the mechanisms underlying beta-adrenergic antagonism and also illuminates novel rationales behind the use of perioperative beta-AAs from a biological point of view. Particularly, it delineates new concepts of beta-adrenergic signal transduction emerging from transgenic animal models. The role of the different characteristics of various beta-AAs is discussed, and evidence will be presented for the selection of one specific agent over another on the basis of individual drug profiles in defined clinical situations. The salutary effects of beta-AAs on the cardiovascular system will be described at the cellular and molecular levels. Beta-AAs exhibit many effects beyond a reduction in heart rate, which are less known by perioperative physicians but equally desirable in the perioperative care of high-risk cardiac patients. These include effects on core components of an anaesthetic regimen, such as analgesia, hypnosis, and memory function. Despite overwhelming evidence of benefit, beta-AAs are currently under-utilized in the perioperative period because of concerns of potential adverse effects and toxicity. The effects of acute administration of beta-AAs on cardiac function in the compromised patient and strategies to counteract potential adverse effects will be discussed in detail. This may help to overcome barriers to the initiation of perioperative treatment with beta-AAs in a larger number of high-risk cardiac patients undergoing surgery.

Peripheral blood natural killer cell cytotoxicity after damage to the limbic system in the rat

The present work was aimed at examining the possible involvement of different parts of the septal area (dorsal, medial, lateral, and septohypothalamic nucleus), the basolateral amygdala, and the bed nucleus of the stria terminalis (BNST) in the regulation of the cytotoxic activity of NK cells (NKCC). The experimental approach included performing electrolytic (or sham) lesions in the tested brain areas and to measuring the peripheral blood NKCC (chromium-51 release assay), the number of leukocytes and lymphocytes, and the plasma corticosterone levels both before and at different time points after the lesion. Lesions were also induced in the three extralimbic structures: the paraventricular hypothalamic nucleus (PVN), the dorsal caudate-putamen, and the cerebellum. To test for a possible effect on NKCC of stress associated with blood collection, anesthesia, cranial surgery, and passing electric current through the brain the proper control experiments were also performed. Lesions of the medial septum and BNST caused gradual depression of NKCC, which peaked on the 10th day after the lesion, followed by a recovery to the baseline on days 21 (medial septum) and 42 (BNST) postinjury. In the respective sham-lesioned groups, mere insertion of electrodes into the medial septum and BNST evoked transient enhancement of NKCC (on the 3rd postlesion day), probably resulting from mechanical stimulation of the nervous tissue. Destruction of the other limbic and extralimbic structures appeared ineffective. After PVN lesions NKCC remained unchanged, despite an approximately 60% decrease in the basal corticosterone level. No adverse effects of the experimental and surgical procedures on NKCC, leukocyte and lymphocyte number, and corticosterone level were found, indicating that electrolytic lesions and other stereotaxic techniques can be safely used to study the brain-immune system interactions. The results obtained raise the question about the interrelationship between the medial septum and the hippocampal formation, BNST, the medial amygdala, and the hypothalamus (both medial and lateral) as a possible circuit involved in the regulation of cellular immune functions.

Postganglionic, direct axo-axonal contacts on the splenic nerve

The splenic nerve is made up almost exclusively of adrenergic fibers. Consequently it was used as a model system in the study of autonomic sympathetic neurotransmission. The splenic nerve regulates the vasoconstriction and volume reduction of the spleen. Brain-immune interactions via modulation of the splenic nerve activity may regulate peripheral cellular immunity. An inhibition of noradrenaline release by alpha(2)-adrenoceptor activation has been reported. As we were interested in a structurally detailed distribution of synaptophysin, immunocytochemical methods were applied to splenic nerve axons. In 1 microm plastic sections a network of synaptophysin-positive varicosities could be observed all along the splenic nerve. They were also positive for dopamine-beta-hydroxylase and cytochrome b561. At the ultrastructural level the varicosities were seen to establish direct contact with the splenic axons. In normal morphology the varicosities revealed small synaptic vesicles and several dense granules. It is demonstrated that a network of direct symmetric contacts of adrenergic nature is present all along the nerve. These terminals may have an inhibitory effect on the splenic nerve activity via axonal receptors. This finding opens new perspectives for the study of the splenic nerve in general and more particularly for its role in the regulation of peripheral cellular immunity.

Activity-wheel running blunts suppression of splenic natural killer cell cytotoxicity after sympathectomy and footshock

We used chemical sympathectomy by 6-hydroxydopamine (6-OHDA) to examine whether adaptation by the sympathetic nervous system (SNS) is a plausible explanation for our prior finding that activity-wheel running blunts the suppression of splenic natural killer cell cytotoxicity after footshock. Male Fischer rats were assigned to treatments using a group (activity wheel vs. sedentary)x treatment (6-OHDA vs. saline)x condition (footshock vs. no shock) design. After 5-6 weeks, rats were injected i.p. with saline or with 40, 80, and 80 mg/kg 6-OHDA on pre experimental days -5, -3, and -1. Half the rats received 6 min of random footshock during a 40-min period. Cytotoxicity was determined by standard 4-h 51Cr release assay. Sympathectomy reduced splenic [NE] by 72%. After 6-OHDA injection and footshock, percent lysis was 33% lower in sedentary rats compared with activity-wheel runners and home-cage controls, p=0.048. The results suggest that activity-wheel running leads to adaptations that offset an altered SNS modulation of splenic NK cell cytotoxicity in response to footshock.

Acetylcholinesterase activity in rat thymus after immunostimulation with interleukin beta

The occurrence and distribution of Acetylcholinesterase (AChE) activity were examined in the thymus of normal and immuno-stimulated adult and aged rats using biochemical and enzymehistochemical methods. Specific AChE reactivity was found primarily in the arteries and, to a lesser extent, in the veins. Only a small amount of activity could be observed in association with the subcapsular and medullary part of the parenchyma and nerve fibers. Our findings indicate that AChE activity in the rat thymus increases after treatment with interleukin beta. In fact treatment with interleukin beta induces an increase of protein content, of the amounts of AChE biochemically assayed and at the levels of AChE histoenzymatically stained. Furthermore, staining of the different structures of the thymus in treated or untreated rats shows that the significant modifications concern the parenchyma, the structures resembling nerve fibers and the whole thymus, while only small changes are observed in AChE activity located in the walls of arteries, veins and lymphatic vessels.

Specificity in the organization of the autonomic nervous system: a basis for precise neural regulation of homeostatic and protective body functions

Experimental investigations of the lumbar sympathetic outflow to skin, skeletal muscle and viscera and the thoracic sympathetic outflow to the head and neck have shown that each target organ and tissue is supplied by one or two separate pathways which consists of sets of pre- and postganglionic neurons with distinct patterns of reflex activity. This probably applies to all sympathetic and parasympathetic systems. The specificity of the messages that these peripheral pathways transmit from the central nervous system arises from integration within precisely organized pathways in the neuraxis. The messages in these discrete functional pathways are transmitted to the target tissues often via organized neuroeffector junctions. Modulation in the periphery can occur within each pathway, both in ganglia and at the level of the effector organs. This organization is the basis not only for precise neural regulations of all homeostatic body functions in which the autonomic nervous system is involved but also the basis of one main component in the regulation of protective body functions: (a) Elementary defense behaviors which are organized in the mesencephalon (confrontational defense, flight, quiescence), (b) regulation of the immune system by the sympathetic nervous system, and (c) adaptive autonomic motor responses during basic emotions require precisely working autonomic, in particular sympathetic, systems. In this sense, the concept of the functioning of the sympathetic nervous system in an "all-or-none" fashion, without distinction between different effector organs, and of simple functional antagonistic organization between sympathetic and parasympathetic nervous system is misleading, inadequate and untenable.

Enhancement of natural immunity seen after voluntary exercise in rats. Role of central opioid receptors

Chronic voluntary exercise in wheels for 5 weeks in spontaneously hypertensive rats (SHR) augments in vivo natural killer (NK) cell cytotoxicity. Endogenous beta-endorphin is increased in cerebrospinal fluid after voluntary exercise in rats and we have recently shown that beta-endorphin administered i.c.v. augments NK cell mediated cytotoxicity in vivo in a similar way as chronic voluntary exercise. We have now further investigated the involvement of central opioid systems in the exercise-induced augmentation in natural immunity. Exercise consisted of voluntary running in wheels for 5 weeks. In vivo cytotoxicity was measured as clearance of injected 51Cr-labeled YAC-1 lymphoma cells from the lungs. The clearance of YAC-1 cells in vivo was significantly increased in runners as compared to sedentary controls. Selective delta, kappa, or mu-opioid receptor antagonists were administered i.c.v. with osmotic minipumps during the last 6 days of the 5 weeks of running. The delta-receptor antagonist naltrindole (40-50 microg/day) significantly but not completely inhibited the enhanced NK-cell cytotoxicity seen after 5 weeks of exercise. Neither the kappa-receptor antagonist nor-BNI or the mu-receptor antagonist beta-FNA influenced the augmentation in NK cell cytotoxicity. Nor-BNI per se significantly augments in vivo cytotoxicity, indicating some inhibiting effect on natural immunity that could be mediated through the kappa-opioid receptor. Our data suggest the involvement of central delta-opioid receptors in the enhancement of natural cytotoxicity seen after chronic voluntary exercise.