Establishment of a continuous cell line from a human carcinoid of the small intestine (KRJ-I)

A new continuous cell line from a human malignant carcinoid of the small intestine (KRJ-I) was established. The cells showed morphological and immunocytochemical features of the tumor of origin and expressed estrogen receptors. The cells are growing as a suspension, forming multicellular aggregates and spheroids. Electron microscopy confirmed the presence of neuroendocrine granules. Dose-dependent growth inhibition was observed after incubation with 5-azacytidine. Cytogenetic analyses of the tumor of origin, the cell line KRJ-I and a liver metastasis KRJ-II revealed clonal tetraploidy and clonal loss of the Y-chromosome and chromosome 19.

Prolonged alpha-adrenergic stimulation causes changes in leukocyte distribution and lymphocyte apoptosis in the rat

We have previously shown in the rat model that acutely or chronically increased peripheral catecholamines lead to suppression of lymphocyte responsiveness via alpha(2)-adrenoceptor activation. Here we investigated the effects of alpha-adrenergic treatment on total leukocyte numbers and proportions of leukocyte subsets in peripheral blood and lymphoid tissues. It was found that a 12-h treatment with subcutaneously implanted tablets, one containing norepinephrine (NE) and one propranolol, leads to an increase in total blood leukocyte counts, due to a pronounced increase in granulocytes. In contrast, the numbers of all classes of lymphocytes other than NK cells were decreased. This decrease in blood lymphocytes is apparently not due to redistribution, since in the thymus, spleen, mesenteric and peripheral lymph nodes, the total numbers of lymphocytes were decreased as well, without any changes in subpopulations. Analogous results were obtained with rats adrenalectomized before the catecholamine treatment. Animals that received the alpha-adrenergic treatment displayed significantly more apoptotic cells in the lymphoid organs, as determined by the TUNEL technique. In the spleen, the enhanced rate of apoptosis was confined to the white pulp; red pulp areas exhibited significantly fewer apoptotic cells. Thus, an increased alpha-adrenergic tone in rats led to a general loss of lymphocytes due to lymphocyte directed apoptosis that was independent of glucocorticoids.

Mens sana in corpore sano--and vice versa. The role of the autonomic nervous system in the immune-neuroendocrine dialogue

Adrenergic and cholinergic transmitters of the autonomic nervous system have important roles in the mutual interrelationships between the brain and the immune system. Besides expressing functional adrenergic and cholinergic receptors, lymphocytes and other immune cells were found to synthesize and release catecholamines and acetylcholine pointing to a possible role of these mediators in the intrinsic regulation of the immune system. In this review we will summarize concepts of Psychoneuroimmunology on the basis of data as obtained in vitro and in experimental studies in animal models, and discuss their relevance to human clinical medicine.

Gene expression of the key enzymes of melatonin synthesis in extrapineal tissues of the rat

Besides the pineal gland, melatonin is reported to be produced in a number of extrapineal sites, where it could act as an intracellular mediator or paracrine signal in addition to its endocrine effects. In view of the suggested immunoregulatory role of melatonin, we compared lymphoid organs and several other tissues of the rat for their potential to synthesize melatonin. Using the reverse transcription-polymerase chain reaction (RT-PCR) method, we determined the tissue-specific expression of mRNAs encoding two key enzymes of the melatonin biosynthesis: serotonin-N-acetyltransferase (NAT) and hydroxyindole-O-methyltransferase (HIOMT). The minimal number of PCR cycles required to obtain a positive signal served as a measure for the abundance of a given mRNA. NAT and HIOMT mRNAs were detected in all tested tissues at high numbers of PCR cycles (40 and 45, respectively). At 35 cycles, only gut, testis, spinal cord, raphe nuclei, stomach fundus and striatum yielded positive signals for both enzymes. In conclusion, the presence of NAT and HIOMT mRNAs in a wide range of tissues corroborates and extends the notion of extrapineal melatonin synthesis. Comparatively low levels of the HIOMT messages in lymphoid organs, however, indicate a limited significance of melatonin synthesis within the immune system.

The dialogue between the brain and immune system involves not only the HPA-axis

Starting out from our previous observations that defects in the immune system-brain feedback predispose to pathogenic immune responses, our interest focuses at the roles of adrenergic/cholinergic neurotransmitters in brain-immune interactions. We have shown in rodent models that 1) both catecholamines and acetylcholine are potent modulators of peripheral immune functions, 2) cholinergic signals are involved in the afferent signalling of the immune system, and 3) lymphocytes not only express functional adrenergic and cholinergic receptors, but synthesize and release neurotransmitters, such as acetylcholine, in quantitative dependence of differentiation and activation. Studies are presently being initiated to investigate the role(s) of these non-neuronal neurotransmitters within immune tissues, and to explore the relevance of excitatory amino acids as important central neurotransmitters in the brain-immune system dialogue.

In vivo immunomodulation by peripheral adrenergic and cholinergic agonists/antagonists in rat and mouse models

Our work is devoted to defining relationships between the immune system and the adrenergic and cholinergic systems in vivo. In the rat model, we have shown that the cells of different immune compartments express the genes of a defined set of adrenergic/cholinergic receptors, and it was shown that lymphocytes are a site of non-neuronal production of norepinephrine and acetylcholine. Furthermore, using implantable slow-release tablets containing adrenergic or cholinergic agonists/antagonists, distinct and partly opposite effects were observed on peripheral immune functions. Concerning sympathetic immunoregulation, our data--in contrast to those of other studies--suggest that an enhanced adrenergic tonus leads to immunosuppression primarily via alpha 2-receptor-mediated mechanisms. Beta-blockade strongly enhances this effect, most likely by inhibition of pineal melatonin synthesis. In recent experiments on the kinetics it was found that the continuous alpha-adrenergic treatment entails a strong suppression of cellular responsiveness during the first few hours, which is increasingly followed by a general loss of lymphocytes in blood and lymphoid organs most likely due to enhanced apoptosis. More recently, we have extended our studies to the mouse model. First data obtained with RNAse protection assays suggest a biphasic effect on the gene expression of several cytokines in spleen cells due to adrenergic in vivo treatment.

mRNA expression of serotonin receptors in cells of the immune tissues of the rat

Serotonin (5-hydroxytryptamine, 5-HT) has been shown to play a role in immunoregulation; however, little is known about specific subtypes of 5-HT receptors involved in peripheral immunomodulation. In the present study we used RT-PCR methods to examine the mRNA expression of 5-HT receptors in the cells of lymphoid tissues of the rat. All 13 rat 5-HT receptor genes cloned so far were examined in ex vivo isolated spleen, thymus, and peripheral blood lymphocytes, as well as in mitogen-stimulated spleen cells. Positive signals were obtained for 5-HT1B, 5-HT1F, 5-HT2A, 5-HT2B, 5-HT6, and 5-HT7 receptor mRNAs in all three compartments. Mitogen (ConA and PWM) stimulated cells additionally expressed mRNA corresponding to the 5HT-3 receptor subtype. In contrast, 5-HT1A, 5-HT1D, 5-HT2C, 5-HT4, 5-HT5A, and 5-HT5B mRNAs were not detected in any of the examined cell populations. These results may be useful as a starting point for future functional studies on immunomodulatory effects of 5-HT and may help to understand conflicting serotonergic effects on immune functions as found in the literature.

A possible role for acetylcholine in the dialogue between thymocytes and thymic stroma

In this article we will review data suggesting that acetylcholine takes part in the mutual interplay between developing T cells and thymic epithelium, and thereby may influence the generation of the T-cell repertoire. In the first part we will recapitulate our findings according to which cholinergic agonists affect thymocyte apoptosis via a nicotinergic effect on thymic epithelial cells. In the second part we will present evidence that acetylcholine within the thymus is mainly derived from the thymocytes themselves, and that the production and release of this neurotransmitter is dependent on activation of thymic lymphocytes.

First continuous human pheochromocytoma cell line: KNA. Biological, cytogenetic and molecular characterization of KNA cells

Pheochromocytomas are rare tumours, with an incidence of 1-2 per million which arise from chromaffin cells of the adrenal medulla. They occur sporadically or as part of dominantly inherited cancer syndromes like multiple endocrine neoplasia 2 (MEN2A and 2B) and others. Continuous cell lines, not available so far, are essential tools for studies in these tumours. A continuous cell line (KNA) was established from a sporadic pheochromocytoma of the right adrenal gland of a 73-year-old woman. The KNA cells grow as suspensions of spheroids and show the morphological and immunocytochemical characteristics of neuronal chromaffin cells, such as neuroendocrine granules, and positive reactions to chromogranin- and related peptide-, neuron specific enolase and vasoactive intestinal peptide antibodies. Neurite-like processes are formed after addition of nerve growth factor. Chromosomal analyses revealed a diploid (46,XX,n = 50) to hypodiploid (43-45,XX,n = 15) karyotype. In hypodiploid metaphases most frequently #19, #17, #21 and #22 were missing. Chromosome arms 1p and 4q showed apparently consistent interstitial deletions: 6q, 8q, 13q and 22q showed clonal interstitial deletions. The cell line shows a heterozygous sequence variant TGC (cysteine) to TGG (tryptophan) in codon 611 in exon 10 of the RET proto-oncogene. So far, PC-12, a rat adrenal pheochromocytoma, has been the only continuous pheochromocytoma cell line available. KNA represents the first report on a human continuous pheochromocytoma cell line, the first report of structural chromosome aberrations in pheochromocytomas and the first report of a RET mutation TGC to TGG in exon 10 of the RET proto-oncogene in a sporadic pheochromocytoma.

Rat lymphocytes produce and secrete acetylcholine in dependence of differentiation and activation

Previous data from this laboratory suggested for the first time that immune cells of the immune system of different species are capable to synthesize the neurotransmitter acetylcholine. In the present study we detected the RNA message for choline acetyltransferase in thymic, splenic and peripheral blood lymphocytes of rats using RT-PCR. Furthermore, using a sensitive radioimmunoassay, we measured acetylcholine in thymic, splenic and peripheral blood lymphocytes. T-cells were found to contain about three times the amount of acetylcholine as compared to B-cells, and CD4+ cells showed significantly higher levels as compared to CD8+ cells. Mitogenic stimulation with PHA increased the acetylcholine levels in lymphoid cells as well as the release into the supernatants.

Adrenergic/cholinergic immunomodulation in the rat model--in vivo veritas?

For several years, our group has been studying the in vivo role of adrenergic and cholinergic mechanisms in the immune-neuroendocrine dialogue in the rat model. The main results of these studies can be summarized as follows: (1) exogenous or endogenous catecholamines suppress PBL functions through alpha-2-receptor-mediated mechanisms, lymphocytes of the spleen are resistant to adrenergic in vivo stimulation, (2) direct or indirect cholinergic treatment leads to enhanced ex vivo functions of splenic and thymic lymphocytes leaving PBL unaffected, (3) cholinergic pathways play a critical role in the "talking back" of the immune system to the brain, (4) acetylcholine inhibits apoptosis of thymocytes possibly via direct effects on thymic epithelial cells, and may thereby influence T-cell maturation, (5) lymphocytes of the various immunological compartments were found to be equipped with the key enzymes for the synthesis of both acetylcholine and norepinephrine, and to secrete these neurotransmitters in culture supernatants.

Characterization of the spontaneous apoptosis of rat thymocytes in vitro

Unlike splenic or blood lymphocytes, rat thymocytes spontaneously undergo continuously increasing apoptosis during culture. In this study we characterized apoptotic thymus cells of rats according to cell size, nuclear dye binding and surface marker expression. Furthermore, the effects of cell density in culture, the age of the donor animals, glucocorticoids, and inhibition of protein synthesis were studied. It was found that: (1) apoptotic rat thymocytes are recognized in flow cytometry as small, acridine orange low, CD4low, CD8high cells; (2) the rate of apoptosis is dependent on the cell density in the culture in a biphasic manner; (3) thymic apoptosis increases with age of the donor animal in fresh, as well as in 24-hour cultivated cell suspensions; (4) neither adrenalectomy nor in vivo or in vitro treatment with the glucocorticoid antagonist RU 38486 influenced spontaneous apoptosis of thymocytes, and (5) inhibition of protein synthesis, which decreases apoptosis induced by corticosterone, had no effect on spontaneous apoptosis of thymocytes.

Thymocyte-directed enhancement of apoptosis via soluble factor(s) derived from a cortical and a medullary thymic epithelial cell line

Apoptosis of murine thymocytes was examined either in intact fetal thymus lobes or in thymus cell suspensions, both cultured alone or in the presence of either a cortical (TEC 1.4) or a medullary (TEC 2.3) thymic epithelial cell line. Both TECs induced a pronounced increase of apoptosis in 24-h cultivated single thymus cell suspensions but not in spleen or bone marrow cell cultures. Co-culture of thymocytes with murine fibroblasts did not enhance apoptosis of the thymus cells. A similar enhancement of thymocyte apoptosis was observed with dialysed culture supernatants derived from both TEC lines, the active component(s) having a molecular weight of > 30 kDa. In contrast, the cortical TEC 1.4 had a pronounced apoptosis inducing effect on intact fetal thymus lobes cultivated for six days, whereas the medullary TEC 2.3 had only a marginal influence. TEC 1.4 also induced a significant alteration in the ratio of CD4+CD8+ to CD4-CD8- cells. It is concluded that both the cortical and medullary epithelial cell lines are able to induce thymocyte apoptosis but that a large proportion of the cells within the intact thymus stroma is refractory to the respective signal(s) of the medullary epithelial cell line.

Adrenergic suppression of peripheral blood T cell reactivity in the rat is due to activation of peripheral alpha 2-receptors

A 20-h treatment of rats with catecholamines using s.c.implantable retard tablets markedly suppresses the in vitro reactivity of peripheral blood (PBL) T lymphocytes, provided that beta-receptors are blocked with propranolol (Felsner et al., 1992). The results can be summarized as follows: (i) the suppressive effect of noradrenaline+propranolol to the concanavalin A (ConA) response of PBL was abolished by the simultaneous application of the alpha-blocker phentolamine. Using selective agonists, the relevant receptor was identified to belong to the alpha 2-subtype. (ii) The alpha-adrenergic suppression of the PBL T cell response was likewise observed in adrenalectomized animals, which rules out the participation of secondarily induced glucocorticoids. Furthermore, the combination of noradrenaline with the watersoluble beta-blocker nadolol was equally effective to suppress the ConA response of PBL. (iii) An analogous alpha-mediated suppression of T cell function of PBL, but not spleen cells, was observed 1 h after i.p. treatment with tyramine, which leads to the release of endogenous noradrenaline. From these results it is concluded that the adrenergic suppression of PBL T cell functions is primarily due to the activation of peripheral alpha 2-receptors and that it is likewise observed under acute indirect sympathomimetic treatment.

Cholinergic signals to and from the immune system

This article reviews recent data from our laboratory towards the impact of the autonomous nervous system on mutual interactions between the immune system and the central nervous system. Using a pharmacological approach in rats it is shown that shifts in the adrenergic/cholinergic balance in vivo affect in vitro functions of the non-specific and specific immune system, whereby adrenergic and cholinergic stimulation in general have opposite effects. A high degree of integration appears to exist between cells of the immune system with the cholinergic system. Lymphocytes were found to react to acetylcholine, but are also able to produce and to degradate this neurotransmitter. In addition, changes in the cholinergic tonus were found to affect immune signaling to the brain and to protect thymocytes from apoptosis, possibly via a direct effect on thymic epithelial cells.

Cholinergic stimulation modulates apoptosis and differentiation of murine thymocytes via a nicotinic effect on thymic epithelium

Effects of cholinergic agonists/antagonists on apoptosis and differentiation of murine thymus cells were investigated in two in vitro models. Treatment with 10(-7) M carbachol was found to counteract the effects of a cortical thymus epithelial cell line (TEC 1.4), on apoptosis and the ratio of CD4 CD8 DP/DN cells in cocultured fetal thymus lobes. A medullary line (TEC 2.3) did not influence apoptosis in fetal thymus lobes. Both TEC lines had the same strong apoptotic effect on thymus cells in suspension, but only the effect of TEC 1.4 was counteracted by carbachol. This cholinergic influence on TEC 1.4 cells is mediated via nicotinic cholinergic receptors, since d-tubocurarine, but not atropine, effectively blocked the effect of carbachol. The results suggest that cholinergic signals to thymic epithelial cells may have regulatory influence on thymic differentiation and selection processes.

Detection of choline-acetyltransferase activity in lymphocytes

The cholinergic system takes part in the immune-neuroendocrine integration. Lymphocytes have been found to express muscarinic and nicotinic cholinergic receptors, as well as acetylcholine-esterase on their surface, and cholinergic agents modulate immune functions in vitro and in vivo. In the present study we provide evidence that purified organ resident and circulating lymphocytes, as well as various lymphoid cell lines derived from different species, exhibit choline-acetyltransferase activity and, therefore, have the potential to produce the neurotransmitter acetylcholine.

A tail-artery cannulation method for the study of blood parameters in freely moving rats

The aim of this study was to improve the chronic tail-artery cannulation technique for repeated substance administration and blood sampling under stress-free conditions in freely moving rats. For that purpose, a special metal capsula and spring-tube system were developed, which not only protects the inserted cannula but also provides a less injurious insertion procedure and improves the animals' welfare as illustrated by normal cleaning and feeding behavior. Intraarterial application of test substances and repeated blood sampling can be done under minimal stress conditions as shown by unaltered plasma levels of highly stress-sensitive prolactin and the catecholamines (CA), epinephrine (E), norepinephrine (NE), and dopamine (DA), after infusion of 300 microL saline.

Opposite effects of mild and severe stress on in vitro activation of rat peripheral blood lymphocytes

The effects of short-term handling and different durations of immobilization on serum levels of catecholamines, ACTH, prolactin, and corticosterone and in vitro functions of lymphocytes were examined in rats. The results show that changes in the immune response of peripheral blood lymphocytes (PBL) depend on the intensity of the stressor: Short (1 min) handling of cannulated rats induced an enhanced stimulation of PBL to respond to T and B cell mitogens, whereas immobilization of the same animals led to suppression, dependent on the time this stressor was applied. The decrease in the mitogen reactivity of PBL after 120 min of immobilization was reversible within 24 h, and could be largely prevented by adrenalectomy, confirming that factors released by this gland are mainly responsible for immunosuppression. In contrast to PBL, spleen cells showed an enhanced mitogen response to immobilization and adrenalectomy, indicating that the immune response is differently regulated in the various compartments of the immune system. Possible correlations of the various effects with changes in stress hormone levels are discussed.

Continuous in vivo treatment with catecholamines suppresses in vitro reactivity of rat peripheral blood T-lymphocytes via α-mediated mechanisms

A 20 h continuous treatment of rats with catecholamines, using subcutaneously implantable retard tablets, had either no (adrenaline, isoproterenol, midodrine) or a slight (noradrenaline) suppressive effect on the in vitro responsiveness of peripheral blood T-lymphocytes. A marked suppression of the mitogen response ensued when adrenaline, noradrenaline or midodrine, but not isoproterenol, was applied together with the beta-receptor blocker propranolol, whereas the combination with the alpha-receptor blocker phentolamine had no effect. The mitogen response of splenic lymphocytes was not affected by any of these treatments. This alpha-mediated adrenergic suppression of peripheral blood T-cells was not correlated with general metabolic alterations, shifts in white blood cell counts or CD4+/CD8+ subsets, or with elevated glucocorticoid levels. The data suggest that to consistently influence the reactivity of rat peripheral blood lymphocytes by chronic adrenergic stimuli in vivo requires both high catecholamine levels and a bias towards alpha-adrenergic receptivity.

The parasympathetic nervous system takes part in the immuno-neuroendocrine dialogue

In a series of experiments the communication between the parasympathetic nervous system and the immune system was examined in rats. The data are summarized as follows: (1) In vivo administration of physostigmine increased the number of plaque-forming cells whereas in vitro addition of cholinergic agonists decreased the specific antibody response. (2) Prolonged in vivo treatment with atropine or physostigmine influenced concanavalin A stimulation of lymphocytes of different compartments in different ways. (3) Immunization with sheep red blood cells changed the number and the affinity of muscarinic cholinergic receptors in the hippocampus. (4) Cholinergic stimulation in vivo inhibited the transient increase of plasma corticosterone following immunization. Our results provide evidence that the parasympathetic nervous system is included in the dialogue between the neuro-endocrine and the immune systems.

Isoprenaline cannot act on pancreatic beta cells without hyperglycemia or alpha-block

During long-term increase in isoprenaline (pronounced beta-effect) and isoprenaline plus regitine (pure beta-effect) pancreatic insulin-secretion still depended mostly on blood glucose levels. This means that increased beta-effect during normo- or hypoglycemia could not cause a higher insulin-secretion. Only during additional alpha-receptor blockade insulin-secretion was slightly but insufficiently increased. Catecholamines seem to be more regulator than originator of the insulin secretory process.

Characterization of 3H-N-methylscopolamine binding to intact rat thymocytes

The binding parameters of muscarinic antagonists in intact rat thymocytes were determined from competitive binding experiments with 3H-N-methylscopolamine (3H-NMS). The muscarinic antagonists inhibited binding of 3H-NMS in a dose-dependent manner. Non-linear regression analysis of the displacement curves indicated the presence of two affinity states for the muscarinic compounds. The beta-blocking agents R-propranolol, S-propranolol and alprenolol inhibited the binding of 3H-NMS to one, low affinity binding site on rat thymic lymphocytes. The ganglionic blocking substance hexamethonium did not affect the binding of 3H-NMS. The results indicate the presence of two binding sites for the radioligand on rat thymocytes, of which only one is specific for muscarinic receptor antagonists.

Binding of muscarine receptor antagonists to pig coronary smooth muscle

In order to characterize the muscarinic binding site on coronary smooth muscle, we investigated the binding properties of (3H)quinuclidinyl benzilate (QNB) in membrane preparations of pig coronary arteries and atria. Scatchard analysis and Hill plot showed that (3H)QNB binds to a single population of sites in both tissues. The binding profiles of the muscarine receptor antagonists atropine, 11-[2-[dimethylamino)methyl)-1-piperidinyl)acetyl)-5,11-dihydro-6H-pyrid o(2,3- b) (1,4)benzodiazepine-6-one (AF-DX 116), pirenzepine, and 4-diphenylacetoxy-N-methylpiperidine methiobromide (4-DAMP) in both tissues were compared with binding data from other tissues, representative for different muscarinic binding site subtypes. It is concluded that the pig coronary smooth muscle muscarinic binding site is different from M1 and M2 binding sites investigated so far.

Preventive action of phentolamine on adrenaline induced blood glucose elevation in humans

A comparison of the action of adrenaline infusion and a combined adrenaline + alpha blocker (phentolamine, Regitine) infusion on blood glucose (BG), plasma immunoreactive insulin (IRI), BG/IRI ratio, C-peptide, and plasma cortisol levels was made in healthy young human subjects. The purpose of the experiment was to check, whether alpha block could abolish adrenaline-induced enhancement of blood glucose levels. The results show that during enhanced adrenaline levels, the use of regitine could indeed normalize blood glucose levels, not so much by increasing the IRI secretion, but by diminishing adrenaline-induced liver glycogenolysis via alpha receptors. This could be a model to prevent stress (adrenaline) induced metabolic deviations in diabetics, especially before and during predictable stress situations, e.g. examinations or surgery.

Decrease of rat-liver-T4-5'-deiodinase activity during chronical isoprenaline beta-action in vivo

Pure adrenergic beta-action, brought about by long-term adrenaline + regitine application in rats, was able to increase liver T4-5'-deiodinase activity for 8 h (Nauman et al. 1984a). Long-term isoprenaline application without alpha-blocking yielded contrary results. One of the compensatory mechanism to be probably blamed could have been the very high endogenous adrenaline-levels (Porta et al. 1985). Simultaneous treatment with isoprenaline and alpha-methyltyrosinemethylester did not settle the problem since even then deiodinase activity was still drastically decreased. Two more components have been found which could very well be the reason for that "paradox beta-action" in vivo, namely very low glucose and insulin levels, both of which are known to influence deiodinase activity. In vivo--contrary to in vitro--it is seemingly not possible that catecholaminergic beta-action could increase the peripheral production of T3 unless general alpha-blocking took place.

Long-term adrenergic beta-action decreases and alpha-action enhances corticosterone levels in rats

A 20 h hyperadrenalinemia in rats was produced by subcutaneously implanted A-retard tablets with an output rate of 1.8 micrograms/min/250 g. This caused a moderate (6 h, 20 h) to expressed (12 h) rise in Corticosterone. Concomitant beta-blockade leads to equal (12 h, 20 h) or even more expressed (6 h) enhancement of plasma corticosterone, while A + alpha-blockade lowers those levels significantly against A or A + Prop treated animals. At 6 and 20 h they are even significantly lower than control values. We therefore conclude that enhanced alpha-adrenergic influence increases and beta-adrenergic influence decreases plasma Corticosterone levels in rats.

Distribution of choline acetyltransferase activity in rat spinal cord--influence of primary afferents?

Choline acetyltransferase (CAT) activity was measured in various regions of rat spinal cord. In the ventral cord, enzyme activity was 2 to 3 times higher than in dorsal cord. In dorsal spinal cord, there was a gradient in enzyme activity, increasing CAT activity being observed in more caudal segments. In autonomic regions intermediate levels were measured. Bilateral transection of the sciatic nerve reduced CAT activity in the ventral horn of lumbar spinal cord, whereas CAT activity in the dorsal horn remained unchanged. Capsaicin pretreatment had no effect on CAT activity in any spinal cord region. Although a similar distribution of cholinergic neurones and primary afferent endings in rat dorsal spinal cord was described, no conclusive statement as to a possible functional interaction can be given.

Long-term application of some catecholamines elevates levels of other catecholamines in rats

Male Sprague-Dawley rats were treated during 20 h with subcutaneously implanted tablets (controlled release systems) containing either adrenaline (A), noradrenaline (NA), isoprenaline (ISO) or just placebos. Levels of the exogenously administered catecholamines (CA) in plasma and liver homogenate were significantly higher than in controls throughout the test time. During NA application endogeneous A and dopamine (DA) plasma values rose considerably, while ISO application enhanced endogenous NA and A levels. Adrenaline application increased NA and DA plasma levels. Several possibilities for this phenomenon are discussed, and it is concluded that previous papers dealing with observations of long term action of CA's should be reevaluated unless the influence of the artificially given CA on the elevation of endogenous CA's has been already taken into consideration.