Effect of long-term intake of liquid nutrition on the development and maintenance of the weight and size of the skull, mandible, and teeth in rats.

The consistency of the diet may affect the development and maintenance of the muscular and bony parts of the masticatory apparatus. Therefore, we investigated the effect of chronic intake of liquid nutrition (Fresubin) on the growth and maintenance of the weight and size of the skull, mandible, and teeth in Wistar rats fed with liquid nutrition during different developmental periods: (i) from weaning to adulthood, (ii) only in the juvenile period, or (iii) only in adulthood. We found that in all groups of rats fed with liquid nutrition, the skull and the mandible were significantly lighter in weight than those of control rats fed exclusively with pelleted chow from weaning to adulthood. In addition, in rats fed with liquid nutrition, the length of the mandible was significantly increased, whereas the height of the mandible and the length of the upper incisors were reduced. Our data indicate that food consistency may profoundly affect the growth pattern and the maintenance of the mass and size of skull bones and teeth during different periods of life. The extent of the effect was found to depend on the period during which liquid nutrition is provided and on the duration of its intake. In conclusion, the findings indicate that prolonged intake of liquid nutrition can significantly affect the development of the bone part of the masticatory apparatus.

Topical application of local anesthetics to melanoma increases the efficacy of anti-PD-1 therapy.

Experimental and clinical data have shown that the nervous system can significantly stimulate the initiation and progression of melanoma. In support of this, approaches that reduce the transmission of signals from peripheral nerves to effector tissues reduce the recurrence of melanoma. Therefore, we investigated the effect of topical application of the local anesthetic Pliaglis (7% lidocaine and 7% tetracaine) on the growth of melanoma induced by intradermal application of B16F0 cells in mice without treatment and in mice treated with the anti-PD-1 antibody. We found that application of Pliaglis to melanoma significantly reduced its growth and this effect was even pronounced in mice treated with the anti-PD-1 antibody. To determine the mechanisms and pathways responsible for the observed effect, the in vitro effect of incubating melanoma cells with lidocaine and/or tetracaine and the in vivo gene expression of cancer and immune-related factors, percentage of immune cells, gene expression of selected neurotransmitter receptors and nerve growth factors in melanoma tissue were studied. We found that lidocaine and tetracaine significantly reduced the viability of B16F0 cells in vitro. In mice with melanoma, Pliaglis potentiated the effect of anti-PD-1 antibody on gene expression of COX-2, IL-1ß, IL-6, CCL11, F4/80, CD206, and NCR1. In addition, Pliaglis increased the gene expression of α9nACHR and 5-HT2a receptors and decreased the gene expression of nerve growth factor receptor (p75NTR) and p53. We also observed Pliaglis-mediated changes in myeloid populations. Topical application of this local anesthetic cream decreased the CD11b+Gr1- population and increased the CD11b+Gr1high population. Our data suggest that Pliaglis reduces melanoma growth through a direct effect on melanoma cells as well as through modulation of the immune response. The involvement of nervous system-related signaling in the inhibitory effect of Pliaglis on melanoma is inconclusive from our data.

Innervation density and types of nerves in prostate cancer.

Innervation of cancerous tissue represents an important pathway enabling the nervous system to influence the processes associated with the initiation, progression, and metastasis of a neoplastic process. In the context of prostate cancer, several papers report the presence of innervation and its modulating effect on the cancer prognosis. However, most of the data are experimental, with limited information on human prostate cancer innervation. Morphometric analysis of archival prostate specimen immunohistochemistry with neural markers PGP9.5 and S100 showed a significant decrease of nerve density in the prostate cancer (n=44) compared to the normal prostate tissue (n=18) and benign prostatic hyperplasia (n=28). Sympathetic nerves were detected with TH, parasympathetic with VAChT, and sensory nerves with SP and CGRP protein detection. Dual immunofluorescence revealed numerous sympathetic nerves in normal prostate and benign prostatic hyperplasia, especially in the peripheral parts. Only a few parasympathetic nerves were found between the glands and in the peripheral parts of the prostate and benign hyperplasia. Sporadic positivity for sensory innervation was present only in approximately 1/10 of nerve fibers, especially in the larger nerves. The pattern of innervation in prostate cancer was analogous to that in normal prostate gland and benign prostatic hyperplasia but there was a significantly lower amount of all nerve types, especially in high-grade carcinoma cases. Although not significant, there was a tendency of decreasing innervation density with increasing Gleason score. Regarding the low density of nerves in prostate carcinoma, the significantly lower PCNA counts in nerves of the cancer specimens cannot be ascribed to lower proliferation activity. Our data confirmed the lower nerve density in the prostate cancer compared to the benign prostate tissue. We could not approve an increased nerve proliferation activity in prostate cancer. All nerve types, most the sympathetic, less the parasympathetic, and the sensory nerves, are present in prostate cancer. The highest nerve density at the periphery of the cancer tissue implies this to be the result of an expansive tumor growth. It is evident that the results of experimental prostate cancer models can be applied to human pathology only to a certain extent. The relation between the range of innervation and the biology of prostate cancer is very complex and will require more detailed information to be applied in therapeutic solutions.

The 24-h pattern of dgcr8, drosha, and dicer expression in the rat suprachiasmatic nuclei and peripheral tissues and its modulation by angiotensin II.

Study was focused on regulatory interactions between the circadian system and the renin-angiotensin system in control of microRNA (miRNA) biosynthesis. Responsiveness of the miRNA biosynthetic pathway, selected pre-miRNAs and clock genes to angiotensin II (AngII) infusion was analysed in the suprachiasmatic nuclei (SCN), liver, kidney and heart during a 24-h cycle. per2 exerted a rhythmic expression profile in all analysed tissues. clock expression showed a rhythmic pattern in the peripheral tissues with tissue-specific response to AngII. dgcr8 expression showed a tissue-specific rhythm only in peripheral tissues, which diminished in the heart and kidney after AngII delivery. Expression of pre-miR-30c was rhythmic in all studied peripheral tissues, pre-miR-34a expression exerted significant rhythm only in the liver. AngII delivery increased expression of pre-miR-30c and pre-miR-34a in the kidney. To conclude, peripheral oscillators are more likely to exhibit rhythmic miRNA biosynthesis responsive to AngII in a tissue-specific manner compared to SCN.

Vagotomy Affects Lipopolysaccharide-Induced Changes of Urocortin 2 Gene Expression in the Brain and on the Periphery.

The corticotropin-releasing hormone family of peptides is involved in regulating the neuroendocrine stress response. Also, the vagus nerve plays an important role in the transmission of immune system-related signals to brain structures, thereby orchestrating the neuroendocrine stress response. Therefore, we investigated gene expression of urocortin 2 (Ucn2) and c-fos, a markers of neuronal activity, within the hypothalamic paraventricular nucleus (PVN), a brain structure involved in neuroendocrine and neuroimmune responses, as well as in the adrenal medulla and spleen in vagotomized rats exposed to immune challenge. In addition, markers of neuroendocrine stress response activity were investigated in the adrenal medulla, spleen, and plasma. Intraperitoneal administration of lipopolysaccharide (LPS) induced a significant increase of c-fos and Ucn2 gene expression in the PVN, and adrenal medulla as well as increases of plasma corticosterone levels. In addition, LPS administration induced a significant increase in the gene expression of tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) in the adrenal medulla. In the spleen, LPS administration increased gene expression of c-fos, while gene expression of TH and PNMT was significantly reduced, and gene expression of Ucn2 was not affected. Subdiaphragmatic vagotomy significantly attenuated the LPS-induced increases of gene expression of c-fos and Ucn2 in the PVN and Ucn2 in the adrenal medulla. Our data has shown that Ucn2 may be involved in regulation of the HPA axis in response to immune challenge. In addition, our findings indicate that the effect of immune challenge on gene expression of Ucn2 is mediated by vagal pathways.

Shank3 Deficiency is Associated With Altered Profile of Neurotransmission Markers in Pups and Adult Mice.

Alterations in the balance between excitation and inhibition, especially in the brain's critical developmental periods, are considered an integral part of the pathophysiology of autism. However, the precise mechanisms have not yet been established. SH3 and multiple Ankyrin repeat domains 3 (Shank3) deficient mice represent a well-established transgenic model of a neurodevelopmental disorder with autistic symptomatology. In this study, we characterize the consequences of Shank3 deficiency according to (1) expression of specific markers of different neuronal populations in pups and adult mice and (2) social behaviour and anxiety in adult mice. Our research found enhanced expression of serotonin transporter and choline acetyltransferase in the hippocampus and hypothalamus in Shank3-deficient pups. We demonstrated marked brain region differences in expression of excitatory glutamatergic markers in pups and adult Shank3 deficient mice. We also observed reduced expression of inhibitory GABAergic markers and GABA receptor subunits in several brain areas in both pups and adult Shank3 deficient mice. Further analysis of dopaminergic brain areas (nucleus accumbens, ventral tegmental area) revealed lower expression levels of GABAergic markers in adult Shank3 deficient mice. Adult Shank3- deficient mice exhibited excessive repetitive behaviour, a higher level of anxiety, and lower locomotor activity. Our data support the theory of an imbalance between excitatory and inhibitory neurotransmission in conditions of abnormal SHANK3 protein. We therefore suggest that autism-like conditions are accompanied by reduced expression of GABAergic markers in the brain during early development as well as in the adult age, which could be associated with long-lasting behavioural abnormalities.

Chronic propranolol treatment moderately attenuated development of N-methyl-N-nitrosourea-induced mammary carcinoma in female rats.

The sympathetic nervous system participates in the development and progression of several cancer types and this effect is mediated mainly via ß-adrenergic signaling. However, the potential of ß-adrenergic signaling blockade to prevent cancer development after exposure to carcinogens has not been investigated, yet. Therefore, in our study, we determined the effect of the ß-blocker propranolol on the development and progression of mammary cancer induced in female rats by administration of the chemical carcinogen N-methyl-N-nitrosourea (MNU). The propranolol treatment (20 mg/kg body weight) started 12 days after MNU administration and lasted 10 weeks. We found that both saline and propranolol treatment significantly increased gene expression of the catecholamine-synthesizing enzyme tyrosine hydroxylase, indicating that repeated injection of saline or propranolol-induced stress in these two groups. However, compared to the vehicle-treated group, propranolol slightly delayed the development and moderately reduced the incidence of mammary carcinoma in animals. To evaluate the mechanisms mediating the effect of propranolol on the development of MNU-induced cancer, we investigated several parameters of the tumor microenvironment and found that propranolol increased gene expression of Casp3. Our data indicate that propranolol treatment that starts after exposure to carcinogens might represent a new, useful approach for preventing the development of cancer, especially in stressed individuals. However, the potential efficiency of propranolol treatment for preventing cancer development and progression in individuals exposed to carcinogens needs further investigation.

Neurobiology of Cancer: Introduction of New Drugs in the Treatment and Prevention of Cancer.

Research on the neurobiology of cancer, which lies at the border of neuroscience and oncology, has elucidated the mechanisms and pathways that enable the nervous system to modulate processes associated with cancer initiation and progression. This research has also shown that several drugs which modulate interactions between the nervous system and the tumor micro- and macroenvironments significantly reduced the progression of cancer in animal models. Encouraging results were also provided by prospective clinical trials investigating the effect of drugs that reduce adrenergic signaling on the course of cancer in oncological patients. Moreover, it has been shown that reducing adrenergic signaling might also reduce the incidence of cancer in animal models, as well as in humans. However, even if many experimental and clinical findings have confirmed the preventive and therapeutic potential of drugs that reduce the stimulatory effect of the nervous system on processes related to cancer initiation and progression, several questions remain unanswered. Therefore, the aim of this review is to critically evaluate the efficiency of these drugs and to discuss questions that need to be answered before their introduction into conventional cancer treatment and prevention.

Changes in gene expression in brain structures related to visceral sensation, autonomic functions, food intake, and cognition in melanoma-bearing mice.

The brain exerts complex effects on the initiation and progression of cancer in the body. However, the influence of cancer localized in peripheral tissues on the brain has been only partially described. Therefore, we investigated gene expression in brain structures that participate in transmitting viscerosensory signals, regulating autonomic functions and food intake, as well as cognition in C57Bl/6J mice with B16-F10 melanoma. In addition, we investigated the relationship between peripheral inflammation and neuroinflammation. We found increased neuronal activity in the nucleus of the solitary tract of tumor-bearing mice, whereas neuronal activity in the A1/C1 catecholaminergic cell group, parabrachial nucleus, lateral hypothalamic area, ventromedial nucleus of the hypothalamus, paraventricular nucleus of the hypothalamus, and hippocampus was decreased. In the majority of investigated brain structures, we found increased gene expression of IL-1ß, whereas gene expression of IL-6 and NF-κB was reduced or unchanged compared with controls. Melanoma-bearing mice also showed increased gene expression of tyrosine hydroxylase in the A1/C1 catecholaminergic cell group, nucleus of the solitary tract, and locus coeruleus, as well as reduced mRNA levels of hypocretin neuropeptide precursor protein in the lateral hypothalamic area, and proopiomelanocortin in the arcuate nucleus. In addition, we found reduced mRNA levels of Bcl-2, brain-derived neurotrophic factor, and doublecortin in the hippocampus. Our data indicate that skin melanoma induces complex changes in the brain, and these changes are most probably caused by cancer-related signals mediated by pro-inflammatory cytokines.

Increased cancer incidence in "cold" countries: An (un)sympathetic connection?

Published data has shown that there is an unexpected, significantly increased cancer mortality and incidence in countries with low or subnormal environmental temperatures. There have been several hypotheses developed to elucidate the mechanisms behind these findings. It is well documented that cold represents a very efficient stressor that activates sympathetic nerves and increases tissue and plasma norepinephrine levels. Importantly, recently accumulated data indicate that norepinephrine can stimulate carcinogenesis and the progression of cancer. Therefore, we suggest that the effect of a cold environment on cancer incidence and mortality might be mediated, at least partially, by norepinephrine released from sympathetic nerves in response to cold. Data supporting this hypothesis are discussed here and potential preventive approaches are described.

Neurobiology of Cancer: the Role of ß-Adrenergic Receptor Signaling in Various Tumor Environments.

The development and progression of cancer depends on both tumor micro- and macroenvironments. In addition, psychosocial and spiritual "environments" might also affect cancer. It has been found that the nervous system, via neural and humoral pathways, significantly modulates processes related to cancer at the level of the tumor micro- and macroenvironments. The nervous system also mediates the effects of psychosocial and noetic factors on cancer. Importantly, data accumulated in the last two decades have clearly shown that effects of the nervous system on cancer initiation, progression, and the development of metastases are mediated by the sympathoadrenal system mainly via ß-adrenergic receptor signaling. Here, we provide a new complex view of the role of ß-adrenergic receptor signaling within the tumor micro- and macroenvironments as well as in mediating the effects of the psychosocial and spiritual environments. In addition, we describe potential preventive and therapeutic implications.

Hypothalamic Inflammation at a Crossroad of Somatic Diseases.

Various hypothalamic nuclei function as central parts of regulators that maintain homeostasis of the organism. Recently, findings have shown that inflammation in the hypothalamus may significantly affect activity of these homeostats and consequently participate in the development of various somatic diseases such as obesity, diabetes, hypertension, and cachexia. In addition, hypothalamic inflammation may also affect aging and lifespan. Identification of the causes and mechanisms involved in the development of hypothalamic inflammation creates not only a basis for better understanding of the etiopathogenesis of somatic diseases, but for the development of new therapeutic approaches for their treatment, as well.

Exposure to a single immobilization or lipopolysaccharide challenge increases expression of genes implicated in the development of Alzheimer's disease in the mice brain cortex.

OBJECTIVES: Despite extensive research efforts, mechanisms participating on development of Alzheimer's disease (AD) are covered only partially. Data from the last decades indicate that various stressors, as etiological factors, may play a role of in the AD. Therefore, we investigated the effect of two acute stressors, immobilization (IMO) and lipopolysaccharide (LPS), on the AD-related neuropathology. METHODS: Adult C57BL/6J mice males were exposed to a single IMO stress or a single intraperitoneal injection of LPS (250 µg/kg body weight). After terminating the experiments, the brains were removed and their cortices isolated. Gene expression of pro-inflammatory cytokines, as well as expression of genes implicated in the AD neuropathology were determined. In addition, mediators related to the activation of the microglia, monocytes, and perivascular macrophages were determined in brain cortices, as well. RESULTS: In comparison with the control animals, we found increased gene expression of proinflammatory mediators in mice brain cortex in both IMO and LPS groups. In stressed animals, we also showed an increased expression of genes related to the AD neuropathology, as well as positive correlations between genes implicated in AD development and associated neuroinflammation. CONCLUSIONS: Our data indicate that acute exposure to a strong IMO stressor, composed of the combined physical and psychological challenges, induces similar inflammatory and other ADrelated neuropathological changes as the immune LPS treatment. Our data also indicate that cytokines are most likely released from the peripheral immune cells, as we detected myeloid cells activity, without any microglia response. We hypothesize that stress induces innate immune response in the brain that consequently potentiate the expression of genes implicated in the AD-related neuropathology.

Ivabradine reduces baseline and stress-induced increase of heart rate and blood pressure and modulates neuroendocrine stress response in rats depending on stressor intensity.

Ivabradine, a selective inhibitor of the sinoatrial pacemaker, is used in clinical practice to reduce heart rate. However, its potential effect on the neuroendocrine stress response has not been investigated. Therefore, we determined the effect of administering ivabradine to rats on cardiovascular parameters and plasma levels of epinephrine, norepinephrine, and corticosterone. Ivabradine was administered intraperitoneally 30 min before exposing animals to either handling, restraint, or immobilization stress. Heart rate and blood pressure were monitored telemetrically. Blood samples were collected before, during, and after stressor exposure to determine the extent of the neuroendocrine stress response as reflected by plasma epinephrine, norepinephrine, and corticosterone levels. In animals pretreated with ivabradine, significantly lower values of heart rate and blood pressure were found during both the baseline period and during exposure to stressors, as well as during the rest period following stressor exposure. Ivabradine also significantly reduced handling-induced epinephrine and norepinephrine release into the bloodstream. However, ivabradine significantly potentiated restraint- and immobilization-induced increases of plasma epinephrine levels, whereas stress-induced changes in plasma norepinephrine and corticosterone levels were ambiguous. Our data shows that ivabradine significantly reduces blood pressure in rats during both baseline and stressful conditions, and also affects the neuroendocrine stress response. These findings show that viscerosensory signaling from the cardiovascular system may significantly modulate the neuroendocrine stress response.

Brain Under Stress and Alzheimer's Disease.

Modern society is characterized by the ubiquity of stressors that affect every individual to different extents. Furthermore, experimental, clinical, and epidemiological data have shown that chronic activation of the stress response may participate in the development of various somatic as well as neuropsychiatric diseases. Surprisingly, the role that stress plays in the etiopathogenesis of Alzheimer's disease (AD) has not yet been studied in detail and is therefore not well understood. However, accumulated data have shown that neuroendocrine and behavioral changes accompanying the stress response affect neuronal homeostasis and compromise several key neuronal processes. Mediators of the neuroendocrine stress response, if elevated repeatedly or chronically, exert direct detrimental effects on the brain by impairing neuronal metabolism, plasticity, and survival. Stress-induced hormonal and behavioral reactions may also participate in the development of hypertension, atherosclerosis, insulin resistance, and other peripheral disturbances that may indirectly induce neuropathological processes participating in the development and progression of AD. Importantly, stress-induced detrimental effects as etiological factors of AD are attractive because they can be reduced by several approaches including behavioral and pharmacological interventions. These interventions may therefore represent an important strategy for prevention or attenuation of the progression of AD.

Psychoneuroimmunology of Cancer - Recent Findings and Perspectives.

BACKGROUND: Gallen observed that psychosocial factors influence tumor incidence. Findings of the last decades have enabled us to understand the mechanisms and pathways responsible for this influence. Ader, Solomon, Besedovsky, and other pioneers of psychoneuroimmunology demonstrated that the nervous system can regulate the activity of immune cells. Based on their findings, the mechanisms via which psychosocial stressors potentiate tumor growth indirectly through inhibition of anti-tumor immune cells have been reported. Human tumor innervation, the presence of ß-adrenergic receptors on tumor cells, and the stimulating effect of noradrenaline on tumor growth and metastasis development have revealed that psychosocial stressors have a direct stimulatory effect on tumor growth, mainly via sympathetic nerves. In recent years, the possibility of modulating signal transduction between the nervous system, immune system, and tumor cells, with the intention of inhibiting tumor growth and metastasis, has been intensively investigated. PURPOSE: The aim of this review paper is to provide an overview of recent experimental and clinical findings from psychoneuroimmunological research, which reveal an increasingly complex link between stress and the onset and progression of tumor diseases and provide a basis for the introduction of new therapeutic approaches for the treatment of cancer patients. CONCLUSION: Some approaches tested in psychoneuroimmunological studies reported that they had inhibitory eff ects on cancer growth and used already clinically-approved drugs and psychological procedures, which may facilitate their application in oncology in the near future.

Brain region-specific effects of immobilization stress on cholinesterases in mice.

Brain acetylcholinesterase (AChE) variant AChER expression increases with acute stress, and this persists for an extended period, although the timing, strain and laterality differences, have not been explored previously. Acute stress transiently increases acetylcholine release, which in turn may increase activity of cholinesterases. Also the AChE gene contains a glucocorticoid response element (GRE), and stress-inducible AChE transcription and activity changes are linked to increased glucocorticoid levels. Corticotropin-releasing hormone knockout (CRH-KO) mice have basal glucocorticoid levels similar to wild type (WT) mice, but much lower levels during stress. Hence we hypothesized that CRH is important for the cholinesterase stress responses, including butyrylcholinesterase (BChE). We used immobilization stress, acute (30 or 120 min) and repeated (120 min daily × 7) in 48 male mice (24 WT and 24 CRH-KO) and determined AChER, AChE and BChE mRNA expression and AChE and BChE activities in left and right brain areas (as cholinergic signaling shows laterality). Immobilization decreased BChE mRNA expression (right amygdala, to 0.5, 0.3 and 0.4, × control respectively) and AChER mRNA expression (to 0.5, 0.4 and 0.4, × control respectively). AChE mRNA expression increased (1.3, 1.4 and 1.8-fold, respectively) in the left striatum (Str). The AChE activity increased in left Str (after 30 min, 1.2-fold), decreased in right parietal cortex with repeated stress (to 0.5 × control). BChE activity decreased after 30 min in the right CA3 region (to 0.4 × control) but increased (3.8-fold) after 120 min in the left CA3 region. The pattern of changes in CRH-KO differed from that in WT mice.

Tauopathy in transgenic (SHR72) rats impairs function of central noradrenergic system and promotes neuroinflammation.

BACKGROUND: Brain norepinephrine (NE) plays an important role in the modulation of stress response and neuroinflammation. Recent studies indicate that in Alzheimer's disease (AD), the tau neuropathology begins in the locus coeruleus (LC) which is the main source of brain NE. Therefore, we investigated the changes in brain NE system and also the immune status under basal and stress conditions in transgenic rats over-expressing the human truncated tau protein. METHODS: Brainstem catecholaminergic cell groups (LC, A1, and A2) and forebrain subcortical (nucleus basalis of Meynert), hippocampal (cornu ammonis, dentate gyrus), and neocortical areas (frontal and temporal association cortices) were analyzed for NE and interleukin 6 (IL-6) mRNA levels in unstressed rats and also in rats exposed to single or repeated immobilization. Moreover, gene expression of NE-biosynthetic enzyme, tyrosine hydroxylase (TH), and several pro- and anti-inflammatory mediators were determined in the LC. RESULTS: It was found that tauopathy reduced basal NE levels in forebrain areas, while the gene expression of IL-6 was increased in all selected areas at the same time. The differences between wild-type and transgenic rats in brain NE and IL-6 mRNA levels were observed in stressed animals as well. Tauopathy increased also the gene expression of TH in the LC. In addition, the LC exhibited exaggerated expression of pro- and anti-inflammatory mediators (IL-6, TNFα, inducible nitric oxide synthases 2 (iNOS2), and interleukin 10 (IL-10)) in transgenic rats suggesting that tauopathy affects also the immune background in LC. Positive correlation between NE and IL-6 mRNA levels in cornu ammonis in stressed transgenic animals indicated the reduction of anti-inflammatory effect of NE. CONCLUSIONS: Our data thus showed that tauopathy alters the functions of LC further leading to the reduction of NE levels and exaggeration of neuroinflammation in forebrain. These findings support the assumption that tau-related dysfunction of LC activates the vicious circle perpetuating neurodegeneration leading to the development of AD.

Sympathectomy reduces tumor weight and affects expression of tumor-related genes in melanoma tissue in the mouse.

Accumulated evidence indicates that sympathetic nerves may potentiate tumor growth, including melanoma. To elucidate possible mechanisms for this effect, we performed chemical sympathectomy by intraperitoneal (i.p.) injection of the neurotoxin 6-hydroxydopamine hydrobromide (100 mg/kg of body weight); in nine adult male C57BL/6J mice; nine control mice received i.p. vehicle (VEH). Seven days later, all mice were injected subcutaneously with 3 × 10(3) B16-F10 melanoma cells. Mice were euthanized 20 d after injection of melanoma cells, for measurement of tumor weight and expression of genes related to sympathetic signaling, apoptosis, hypoxia and angiogenesis in tumor tissue. To assess potential involvement of the hypothalamo-pituitary-adrenocortical axis in the effect of sympathectomy on melanoma growth, concentrations of plasma corticosterone and level of glucocorticoid receptor mRNA in tumor tissue were determined. We found that sympathectomy significantly attenuated melanoma growth (tumor weight 0.29 ± 0.16 g versus 1.02 ± 0.30 g in controls; p < 0.05). In tumor tissue from sympathectomized mice, we found significantly increased gene expression (measured by real-time PCR), relative to VEH-injected controls, of tyrosine hydroxylase, neuropeptide Y and glucocorticoid receptor (all p < 0.05), and alpha1, beta1 and beta3 adrenergic receptors (all p < 0.025), and factors related to apoptosis (Bcl-2 and caspase-3; p < 0.05) and hypoxia (hypoxia inducible factor 1 alpha) (p = 0.005). Plasma corticosterone concentrations were significantly elevated (p < 0.05) in these mice. Our findings indicate that sympathectomy induces complex changes in the tumor microenvironment reducing melanoma growth. Such complex changes should be considered in the prediction of responses of cancer patients to interventions affecting sympathetic signaling in tumor tissue and its environment.