Acute Inhibition of Inflammation Mediated by Sympathetic Nerves: The Inflammatory Reflex

In this review, we will try to convince the readers that the immune system is controlled by an endogenous neural reflex, termed inflammatory reflex, that inhibits the acute immune response during the course of a systemic immune challenge. We will analyse here the contribution of different sympathetic nerves as possible efferent arms of the inflammatory reflex. We will discuss the evidence that demonstrates that neither the splenic sympathetic nerves nor the hepatic sympathetic nerves are necessary for the endogenous neural reflex inhibition of inflammation. We will discuss the contribution of the adrenal glands to the reflex control of inflammation, noting that the neurally mediated release of catecholamines in the systemic circulation is responsible for the enhancement of the anti-inflammatory cytokine interleukin 10 (IL-10) but not of the inhibition of the pro-inflammatory cytokine tumour necrosis factor α (TNF). We will conclude by reviewing the evidence that demonstrates that the splanchnic anti-inflammatory pathway, composed by preganglionic and postganglionic sympathetic splanchnic fibres with different target organs, including the spleen and the adrenal glands, is the efferent arm of the inflammatory reflex. During the course of a systemic immune challenge, the splanchnic anti-inflammatory pathway is endogenously activated to inhibit the TNF and enhance the IL-10 response, independently, presumably acting on separate populations of leukocytes.

Synaptotagmin-7 facilitates acetylcholine release in splanchnic nerve-chromaffin cell synapses during nerve activity

Disturbances that threaten homeostasis elicit activation of the sympathetic nervous system (SNS) and the adrenal medulla. The effectors discharge as a unit to drive global and immediate changes in whole-body physiology. Descending sympathetic information is conveyed to the adrenal medulla via preganglionic splanchnic fibers. These fibers pass into the gland and synapse onto chromaffin cells, which synthesize, store, and secrete catecholamines and vasoactive peptides. While the importance of the sympatho-adrenal branch of the autonomic nervous system has been appreciated for many decades, the mechanisms underlying transmission between presynaptic splanchnic neurons and postsynaptic chromaffin cells have remained obscure. In contrast to chromaffin cells, which have enjoyed sustained attention as a model system for exocytosis, even the Ca2+ sensors that are expressed within splanchnic terminals have not yet been identified. This study shows that a ubiquitous Ca2+-binding protein, synaptotagmin-7 (Syt7), is expressed within the fibers that innervate the adrenal medulla, and that its absence can alter synaptic transmission in the preganglionic terminals of chromaffin cells. The prevailing impact in synapses that lack Syt7 is a decrease in synaptic strength and neuronal short-term plasticity. Evoked excitatory postsynaptic currents (EPSCs) in Syt7 KO preganglionic terminals are smaller in amplitude than in wild-type synapses stimulated in an identical manner. Splanchnic inputs also display robust short-term presynaptic facilitation, which is compromised in the absence of Syt7. These data reveal, for the first time, a role for any synaptotagmin at the splanchnic-chromaffin cell synapse. They also suggest that Syt7 has actions at synaptic terminals that are conserved across central and peripheral branches of the nervous system.

Basal and Stress-Induced Network Activity in the Adrenal Medulla In Vivo

The adrenal medulla plays a critical role in mammalian homeostasis and the stress response. It is populated by clustered chromaffin cells that secrete epinephrine or norepinephrine along with peptides into the bloodstream affecting distant target organs. Despite been heavily studied, the central control of adrenal medulla and in-situ spatiotemporal responsiveness remains poorly understood. For this work, we continuously monitored the electrical activity of individual adrenomedullary chromaffin cells in the living anesthetized rat using multielectrode arrays. We measured the chromaffin cell activity under basal and physiological stress conditions and characterized the functional micro-architecture of the adrenal medulla. Under basal conditions, chromaffin cells fired action potentials with frequencies between ~0.2 and 4 Hz. Activity was almost completely driven by sympathetic inputs coming through the splanchnic nerve. Chromaffin cells were organized into independent local networks in which cells fired in a specific order, with latencies from hundreds of microseconds to a few milliseconds. Electrical stimulation of the splanchnic nerve evoked almost exactly the same spatiotemporal firing patterns that occurred spontaneously. Hypoglycemic stress, induced by insulin administration resulted in increased activity of a subset of the chromaffin cells. In contrast, respiratory arrest induced by lethal anesthesia resulted in an increase in the activity of virtually all chromaffin cells before cessation of all activity. These results suggest a stressor-specific activation of adrenomedullary chromaffin cell networks and revealed a surprisingly complex electrical organization that likely reflects the dynamic nature of the adrenal medulla's neuroendocrine output during basal conditions and during different types of physiological stress.

Direct effects of recurrent hypoglycaemia on adrenal catecholamine release

In Type 1 and advanced Type 2 diabetes mellitus, elevation of plasma epinephrine plays a key role in normalizing plasma glucose during hypoglycaemia. However, recurrent hypoglycaemia blunts this elevation of plasma epinephrine. To determine whether recurrent hypoglycaemia affects peripheral components of the sympatho-adrenal system responsible for epinephrine release, male rats were administered subcutaneous insulin daily for 3 days. These recurrent hypoglycaemic animals showed a smaller elevation of plasma epinephrine than saline-injected controls when subjected to insulin-induced hypoglycaemia. Electrical stimulation of an adrenal branch of the splanchnic nerve in recurrent hypoglycaemic animals elicited less release of epinephrine and norepinephrine than in controls, without a change in adrenal catecholamine content. Responsiveness of isolated, perfused adrenal glands to acetylcholine and other acetylcholine receptor agonists was also unchanged. These results indicate that recurrent hypoglycaemia compromised the efficacy with which peripheral neuronal activity stimulates adrenal catecholamine release and demonstrate that peripheral components of the sympatho-adrenal system were directly affected by recurrent hypoglycaemia.

Ageing alters perivascular nerve function of mouse mesenteric arteries in vivo

Abstract  Mesenteric arteries (MAs) are studied widely in vitro but little is known of their reactivity in vivo. Transgenic animals have enabled Ca(2+) signalling to be studied in isolated MAs but the reactivity of these vessels in vivo is undefined. We tested the hypothesis that ageing alters MA reactivity to perivascular nerve stimulation (PNS) and adrenoreceptor (AR) activation during blood flow control. First- (1A), second- (2A) and third-order (3A) MAs of pentobarbital-anaesthetized Young (3-6 months) and Old (24-26 months) male and female Cx40(BAC)-GCaMP2 transgenic mice (C57BL/6 background; positive or negative for the GCaMP2 transgene) were studied with intravital microscopy. A segment of jejunum was exteriorized and an MA network was superfused with physiological salt solution (pH 7.4, 37°C). Resting tone was 10% in MAs of Young and Old mice; diameters were ∼5% (1A), 20% (2A) and 40% (3A) smaller (P 0.05) in Old mice. Throughout MA networks, vasoconstriction increased with PNS frequency (1-16 Hz) but was ∼20% less in Young vs. Old mice (P 0.05) and was inhibited by tetrodotoxin (1 μm). Capsaicin (10 μm; to inhibit sensory nerves) enhanced MA constriction to PNS (P 0.05) by ∼20% in Young but not Old mice. Phenylephrine (an α1AR agonist) potency was greater in Young mice (P 0.05) with similar efficacy (∼60% constriction) across ages and MA branches. Constrictions to UK14304 (an α2AR agonist) were less (∼20%; P 0.05) and were unaffected by ageing. Irrespective of sex or transgene expression, ageing consistently reduced the sensitivity of MAs to α1AR vasoconstriction while blunting the attenuation of sympathetic vasoconstriction by sensory nerves. These findings imply substantive alterations in splanchnic blood flow control with ageing.

PACAP controls adrenomedullary catecholamine secretion and expression of catecholamine biosynthetic enzymes at high splanchnic nerve firing rates characteristic of stress transduction in male mice

The neuropeptide PACAP (pituitary adenylate cyclase-activating polypeptide) is a cotransmitter of acetylcholine at the adrenomedullary synapse, where autonomic regulation of hormone secretion occurs. We have previously reported that survival of prolonged metabolic stress in mice requires PACAP-dependent biosynthesis and secretion of adrenomedullary catecholamines (CAs). In the present experiments, we show that CA secretion evoked by direct high-frequency stimulation of the splanchnic nerve is abolished in native adrenal slices from male PACAP-deficient mice. Further, we demonstrate that PACAP is both necessary and sufficient for CA secretion ex vivo during stimulation protocols designed to mimic stress. In vivo, up-regulation of transcripts encoding adrenomedullary CA-synthesizing enzymes (tyrosine hydroxylase, phenylethanolamine N-methyltransferase) in response to both psychogenic and metabolic stressors (restraint and hypoglycemia) is PACAP-dependent. Stressor-induced alteration of the adrenomedullary secretory cocktail also appears to require PACAP, because up-regulation of galanin mRNA is abrogated in male PACAP-deficient mice. We further show that hypoglycemia-induced corticosterone secretion is not PACAP-dependent, ruling out the possibility that glucocorticoids are the main mediators of the aforementioned effects. Instead, experiments with bovine chromaffin cells suggest that PACAP acts directly at the level of the adrenal medulla. By integrating prolonged CA secretion, expression of biosynthetic enzymes and production of modulatory neuropeptides such as galanin, PACAP is crucial for adrenomedullary function. Importantly, our results show that PACAP is the dominant adrenomedullary neurotransmitter during conditions of enhanced secretory demand.

Agrin mediates a rapid switch from electrical coupling to chemical neurotransmission during synaptogenesis

In contrast to its well-established actions as an organizer of synaptic differentiation at the neuromuscular junction, the proteoglycan agrin is still in search of a function in the nervous system. Here, we report an entirely unanticipated role for agrin in the dual modulation of electrical and chemical intercellular communication that occurs during the critical period of synapse formation. When applied at the developing splanchnic nerve–chromaffin cell cholinergic synapse in rat adrenal acute slices, agrin rapidly modified cell-to-cell communication mechanisms. Specifically, it led to decreased gap junction–mediated electrical coupling that preceded an increase in nicotinic synaptic transmission. This developmental switch from predominantly electrical to chemical communication was fully operational within one hour and depended on the activation of Src family–related tyrosine kinases. Hence, agrin may play a pivotal role in synaptogenesis in promoting a rapid switch between electrical coupling and synaptic neurotransmission.

Simultaneous monitoring of acetylcholine and catecholamine release in the in vivo rat adrenal medulla

To simultaneously monitor acetylcholine release from pre-ganglionic adrenal sympathetic nerve endings and catecholamine release from post-ganglionic adrenal chromaffin cells in the in vivo state, we applied microdialysis technique to anesthetized rats. Dialysis probe was implanted in the left adrenal medulla and perfused with Ringer's solution containing neostigmine (a cholinesterase inhibitor). After transection of splanchnic nerves, we electrically stimulated splanchnic nerves or locally administered acetylcholine through dialysis probes for 2 min and investigated dialysate acetylcholine, choline, norepinephrine and epinephrine responses. Acetylcholine was not detected in dialysate before nerve stimulation, but substantial acetylcholine was detected by nerve stimulation. In contrast, choline was detected in dialysate before stimulation, and dialysate choline concentration did not change with repetitive nerve stimulation. The estimated interstitial acetylcholine levels and dialysate catecholamine responses were almost identical between exogenous acetylcholine (10 microM) and nerve stimulation (2 Hz). Dialysate acetylcholine, norepinephrine and epinephrine responses were correlated with the frequencies of electrical nerve stimulation, and dialysate norepinephrine and epinephrine responses were quantitatively correlated with dialysate acetylcholine responses. Neither hexamethonium (a nicotinic receptor antagonist) nor atropine (a muscarinic receptor antagonist) affected the dialysate acetylcholine response to nerve stimulation. Microdialysis technique made it possible to simultaneously assess activities of pre-ganglionic adrenal sympathetic nerves and post-ganglionic adrenal chromaffin cells in the in vivo state and provided quantitative information about input-output relationship in the adrenal medulla.

The role of intraspinal adenosine A1 receptors in sympathetic regulation

Using a splanchnic nerve-spinal cord preparation in vitro, we have previously demonstrated that tonic sympathetic activity is generated from the thoracic spinal cord. Here, we sought to determine if adenosine receptors play a role in modulating this spinally generated sympathetic activity. Various adenosine analogs were applied. N6-Cyclopentyladenosine (CPA, adenosine A1 receptor agonist) and 5'-N-ethylcarboxamidoadenosine (NECA, adenosine A1/A2 receptor agonist) reduced, while N6-[2-(4-aminophenyl)ethyl]adenosine (APNEA, non-selective adenosine A3 receptor agonist) did not alter sympathetic activity. The inhibitory effect of CPA or NECA on sympathetic activity was reversed by 8-cyclopentyltheophylline (CPT, adenosine A1 receptor antagonist) or abolished by CPT pretreatment. In the presence of 3,7-dimethyl-1-propargylxanthine (DMPX, adenosine A2 receptor antagonist), sympathetic activity was still reduced by CPA or NECA. Sympathetic activities were not changed by applications of the more selective adenosine A2 or A3 receptor agonists or antagonists, including 4-[2-[[6-amino-9-(N-ethyl-beta-D-ribofuranuronamidosyl)-9H-purin-2-yl]amino]ethyl]benzenepropanoic acid (CGS21680), 4-(2-[7-amino-2-(2-furyl)[1,2,4]triazolo[2,3-a][1,3,5]triazin-5-ylamino]ethyl)phenol (ZM241385), 2-chloro-N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (Chloro-IB-MECA), and 3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate (MRS1191). These findings exclude a possible involvement of A2 or A3 receptors in sympathetic regulation at the spinal levels. Interestingly, CPT alone did not affect sympathetic activity, suggesting that adenosine A1 receptors are endogenously quiescent under our experimental conditions. We conclude that intraspinal adenosine A1 receptors may down-regulate sympathetic outflow and serve as a part of the scheme for neuroprotection.

Acetylcholine and potassium elicit different patterns of exocytosis in chromaffin cells when the intracellular calcium handling is disturbed

During fast superfusion of bovine chromaffin cells with normal Krebs-HEPES solution containing 2 mM Ca2+, pulses of 100 microM ACh or 100 mM K+ of increasing duration (1-5 s) caused similar exocytosis of about 3-4 microC catecholamine. Depletion of endoplasmic reticulum (ER) Ca2+ by pretreatment with 1 microM thapsigargin, 10 mM caffeine and 10 microM ryanodine more than halved the responses to ACh but did not affect the responses to K+ responses. In these ER Ca2+-depleted cells the protonophore carbonylcyanide p-(trifluoromethoxy)phenylhydrazone (FCCP) (20 microM given during the 5 s preceding each pulse) augmented the responses to ACh responses fourfold for all pulse durations applied (1-5 s) whereas responses to K+ were potentiated twofold with 1 to 2 s pulses but were not affected with longer pulse durations. ACh pulses applied to fura-2-loaded cells evoked increases of bulk cytosolic [Ca2+] ([Ca2+](c)) that were substantially smaller than those elicited by K+ pulses. Confocal microscopy of fluo-3-loaded cells showed that ACh pulses elicited discrete and more localized [Ca2+](c) elevations, whereas K+ pulses produced higher [Ca2+](c) transients that spread out quickly throughout the cytosol. These results suggest that mitochondria sense the increase of local [Ca2+](c) elicited by ACh (that evokes firing of action potentials) much better than that induced by K+ (that produces sustained cell depolarisation). This implies that mitochondria are more sensitive to the local [Ca2+](c) changes resulting from the physiological triggering of action potentials by ACh.

PACAP-(1-38) as neurotransmitter in the porcine adrenal glands

The concentration of pituitary adenylyl cyclase-activating polypeptide [PACAP-(1-38)] in porcine adrenal glands amounted to 14 +/- 3 pmol/g tissue. PACAP immunoreactive (PACAP-IR) fibers innervated adrenal chromaffin cells (often co-localized with choline acetyltransferase). Subcapsular fibers traversed the cortex-innervating endocrine cells and blood vessels [some co-storing mainly calcitonin gene-related peptide but also vasoactive intestinal polypeptide (VIP)]. PACAP-IR fibers were demonstrated in the splanchnic nerves, whereas IR adrenal nerve cell bodies were absent. In isolated, vascularly perfused adrenal gland, splanchnic nerve stimulation (16 Hz) and capsaicin (10(-5) M) increased PACAP-(1-38) release (1.6-fold and 6-fold respectively, P = 0.02). PACAP-(1-38) dose-dependently stimulated cortisol (2 x 10(-10) M; 24-fold increase, P = 0.02) and chromogranin A fragment (2 x 10(-9) M; 15-fold increase, P = 0.05) secretion. Both were strongly inhibited by the PAC(1)/VPAC(2) receptor antagonist PACAP-(6-38) (10(-7) M). PACAP-(6-38) also inhibited splanchnic nerve (10 Hz)-induced cortisol secretion but lacked any effect on splanchnic nerve-induced pancreastatin secretion. PACAP-(1-38) (2 x 10(-10) M) decreased vascular resistance from 5.5 +/- 0.6 to 4.6 +/- 0.4 mmHg. min. ml(-1). PACAP-(6-38) had no effect on this response. We conclude that PACAP-(1-38) may play a role in splanchnic nerve-induced adrenal secretion and in afferent reflex pathways.

Role of brain angiotensin II in renal nerve inhibition elicited by volume expansion in the conscious rabbit

Losartan (10 microg/25 microl) or vehicle was injected into the fourth brain ventricle prior to volume expansion (VE) with Haemaccel (2 ml/min for 30 min). RSNA was reduced by a maximum of 45% in response to the VE following vehicle and by 33% following losartan. There was no significant difference between the treatments in RSNA, nor in the blood pressure and heart rate responses. We conclude that endogenous angiotensin II does not make a major contribution to the reflex reduction in RSNA initiated by VE.

Changes in proenkephalin gene expression in the developing hamster

Proenkephalin (Penk) gene expression is high in the adult hamster adrenal medulla and it is comparable to that found in both the hamster and rat striatum. In addition, Penk gene expression in the hamster adrenal medulla is more typical of adult mammalian adrenals than the rat. Since the nature of Penk gene expression in the developing hamster adrenal is not known, it was examined and compared to that found in the striatum were adult levels in the adrenal and striatum are similar. The results show that Penk gene expression progressively increases in the developing hamster adrenal to peak on postnatal day 4. There is then a small decline to adult levels by postnatal day 12 when the morphology of the developing adrenal resembles the adult. Functional splanchnic nerve activity, as assessed by the ability of reserpine to induce increases in adrenal tyrosine hydroxylase mRNA, is not present until after postnatal day 4. Therefore, early increases in Penk gene expression are independent of splanchnic nerve activity. Adrenal EC peptides resulting from the developmental increases in Penk gene expression appear to be unprocessed and proenkephalin-like. This is based on the very low levels of free enkephalin (met-enkephalin) detected in the adrenals from both newborn and adult hamsters (1-5% of total EC peptide levels). In the developing hamster striatum, Penk gene expression remains low and unchanged until postnatal day 4 and increases six-fold by adulthood. Free enkephalin (met-enkephalin) levels remain high (between 36 and 88% of total EC peptide levels) in the developing and adult hamster striatum. Therefore the results show early increases in adrenal Penk gene expression in the developing hamster that are independent of splanchnic nerve activity and adult Penk gene expression which is high and dependent on splanchnic nerve activity. This differs from what is observed in the frequently studied rat. However, developmental changes in the hamster striatum are similar to those in the rat.

Differing actions of the acute administration of propranolol and isosorbide-5-mononitrate on the portal circulation

BACKGROUND

The aim of this study was to clarify the actions of propranolol and isosorbide-5-mononitrate upon the portal circulation.

METHODS

Portal haemodynamics were assessed in 16 patients with transjugular intrahepatic portosystemic stent shunts. A reverse thermodilution catheter was positioned in the portal vein, and portal vein pressure and portal vein flow were measured directly. The effects of propranolol 80 mg and isosorbide-5-mononitrate 20 mg over 1 h were determined independently.

RESULTS

This demonstrated that propranolol reduced both portal pressure gradient (7.7 +/- 2.3 to 5.5 +/- 2.1 mmHg, P < 0.01) and portal vein flow (925 +/- 123 to 597 +/- 99 mL/min, P = 0.01) significantly, implying a reduction in splanchnic inflow as its main effect. In contrast, isosorbide-5-mononitrate tended to increase portal vein flow (814 +/- 186 to 911 +/- 211 mL/min; P = 0.06) whilst reducing portal pressure significantly (108 +/- 12 to 92 +/- 10 mmHg P = 0.014). This suggests a fall in intrahepatic resistance and provides no evidence for baroreceptor-mediated reflex splanchnic vasoconstriction.

CONCLUSIONS

These drugs act upon different variables contributing to portal hypertension and so they may have a powerful synergistic effect in combination. Direct measurement of portal vein flow is a valuable method for assessing the pharmacological modulation of portal venous inflow.

The depletion of monoamines blocks the sympathoinhibitory response to cocaine

Recent studies have shown that cocaine decreases, rather than increases sympathetic nerve discharge (SND). Whether these sympathoinhibitory responses are the result of cocaine's actions on monoaminergic transmission (i.e. blockade of neuronal uptake or stimulation of transmitter release) or its local anesthetic actions is not known. The purpose of the present study was to determine the degree to which cocaine's actions on monoaminergic transmission are involved in mediating the sympathoinhibitory response to this drug. We examined the mean arterial pressure, heart rate and splanchnic sympathetic nerve responses elicited by cocaine (1 mg/kg, i.v.) in pentobarbital-anesthetized rats depleted of monoamines. Monoamines were depleted by administering reserpine (10 mg/kg, i.p.) either 24, or 48 and 24 h before the experiment. The rats were also given alpha-methyl-p-tyrosine (200 mg/kg, i.p.) 2 h before the experiment. Vehicle-treated rats served as controls. Depletion of monoamines markedly reduced resting arterial pressure and heart rate and significantly attenuated the pressor response and tachycardia elicited by tyramine (1 mg/kg, i.v.). In control rats, cocaine elicited marked (-64 +/- 4%) and prolonged (44 +/- 4 min) decreases in SND. The magnitude (-34 +/- 11%) and duration (23 +/- 6 min) of these responses were significantly attenuated after 1 day of monoamine depletion. After 2 days of depletion, the sympathoinhibitory response was abolished and was replaced by a small, brief increase in SND (10 +/- 3%). The pressor responses were similar in control and depleted rats, while the bradycardic response (-33 +/- 4 bpm) was significantly reduced after 1 and 2 days of monoamine depletion to -20 +/- 3 and -15 +/- 2 bpm, respectively. We conclude that a functionally intact monoaminergic system is essential for the sympathoinhibitory response to cocaine. Whether the pressor responses result from a non-monoaminergic or a reserpine and/or alpha-methyl-p-tyrosine resistant catecholaminergic mechanism is unknown.

Innervation-independent changes in the mRNAs encoding tyrosine hydroxylase and the norepinephrine transporter in rat adrenal medulla after high-dose reserpine

To determine whether a trans-synaptic mechanism triggered the effects of reserpine on adrenomedullary mRNAs encoding the norepinephrine transporter and tyrosine hydroxylase, we administered 10 mg/kg reserpine to rats after unilateral splanchnicotomy, and examined their adrenal medullas using quantitative in situ hybridization. Splanchnicotomy did not alter the decrease in norepinephrine transporter mRNA that follows reserpine administration, but diminished the reserpine-induced increase in tyrosine hydroxylase mRNA by almost 80%. Despite the latter effect, reserpine still induced a significant increase in tyrosine hydroxylase mRNA in denervated adrenal medullas, compared to vehicle-treated adrenal medullas. These results show that a trans-synaptic mechanism does not trigger the decrease in adrenomedullary norepinephrine transporter mRNA following reserpine. In addition, an innervation-independent mechanism mediates a portion of the reserpine-induced increase in adrenomedullary tyrosine hydroxylase mRNA.

Effects of beta adrenoceptor agonists and antagonists on adrenal catecholamine release in response to splanchnic nerve stimulation in anesthetized dogs: role of beta-1 and beta-2 adrenoceptors

The present study was performed to examine whether beta adrenoceptor agonists and antagonists modify the release of adrenal catecholamine (CA) in response to splanchnic nerve stimulation (SNS) in anesthetized dogs, in order to elucidate the beta adrenoceptor-mediated modulation of adrenal CA release. SNS at 3 Hz produced marked increases in both epinephrine and norepinephrine output determined from adrenal venous blood. Atenolol (10, 30 and 100 micrograms/kg, i.v.) and CGP20712A (10 and 30 micrograms/kg, i.v.), selective beta-1 adrenoceptor antagonists, significantly enhanced the SNS-induced increases in CA output. Neither ICI118551 (10, 30 and 100 micrograms/kg, i.v.), a selective beta-2 adrenoceptor antagonist, nor nadolol (10, 30 and 100 micrograms/kg, i.v.), a nonselective beta adrenoceptor antagonist, affected the SNS-induced increases in CA output. After the treatment with ICI118551 (100 micrograms/kg, i.v.), atenolol (10, 30 and 100 micrograms/kg, i.v.) failed to enhance the SNS-induced increases in CA output. On the other hand, neither isoproterenol (0.03 and 0.1 micrograms/kg/min, i.v.) nor the selective beta-2 adrenoceptor agonist procaterol (0.03 and 0.1 micrograms/kg/min, i.v.) affected the SNS-induced increases in CA output. After the treatment with atenolol (100 micrograms/kg, i.v.), both isoproterenol (0.03 micrograms/kg/min, i.v.) and procaterol (0.03 micrograms/kg/min, i.v.) enhanced the SNS-induced increases in CA output. The enhancing effects of isoproterenol and procaterol were abolished by ICI118551 (100 micrograms/kg, i.v.). These results indicate that activation of beta-2 adrenoceptors facilitates the SNS-evoked release of CA from the dog adrenal medulla under the condition in which beta-1 adrenoceptors are blocked, and they suggest that activation of beta-1 adrenoceptors inhibits the beta-2 adrenoceptor-mediated facilitation process of adrenal CA release.

Splanchnic release of potassium after hemorrhage and succinylcholine in rabbits

Recent clinical reports document that hyperkalemia may occur after succinylcholine (SCh) administration in hemorrhagic, acidotic humans. Hemorrhagic, acidotic rabbits are a useful model for study of this phenomenon because of profound hyperkalemia after SCh. To determine the etiology of this hyperkalemia, we anesthetized rabbits (n = 5, Group H) with halothane/N2O, and after endotracheal intubation, placed catheters in the femoral artery, femoral vein (FV), and inferior vena cava (IVC), the latter at or above the hepatic veins. After measurement of baseline K+ (from each catheter) and arterial blood gases, approximately 30 mL/kg of blood was withdrawn, and the animal was allowed to become acidotic until pH approximately 7.00-7.10. Plasma K+ was determined again, and SCh 1 mg/kg administered intravenously. Blood from each catheter was withdrawn for K+ analysis at 1, 3, 5, and 7 min after SCh. Control rabbits (Group C, n = 5) were similarly anesthetized and catheterized but were not hemorrhaged. Arterial blood gas and K+ analyses were performed before and after SCh 1 mg/kg, similar to Group H. In Group H, arterial K+ concentration increased after hemorrhage (3.2 +/- 0.3 mmol/L to 6.4 +/- 2.0 mmol/L, P < 0.05). SCh caused a further increase, peaking at 8.3 +/- 1.5 mmol/L at 7 min (P < 0.05). In Group H the IVC-FV K+ difference was 1.6 +/- 1.9 mmol/L, 1.5 +/- 2.1 mmol/L, 0.9 +/- 1.6 mmol/L and 1.6 +/- 1.4 mmol/L, respectively, for the 1-, 3-, 5-, and 7-min periods after SCh.(ABSTRACT TRUNCATED AT 250 WORDS)

The functional role of opioid receptors in acetylcholine release in the rat adrenal medulla

The functional role of opioid receptors in acetylcholine release from splanchnic nerve terminals in the adrenal medulla was investigated in halothane-anesthetized rats. The extracellular acetylcholine level was measured by a newly developed in vivo adrenal microdialysis method. The potassium (K+)-evoked acetylcholine release from the splanchnic nerve terminals was inhibited by morphine (10 microM), a mu-opioid receptor agonist, and [D-Pen2,D-Pen5]enkephalin (DPDPE, 1 and 10 microM), a delta-opioid receptor agonist. These inhibitory effects of morphine and DPDPE were significantly abolished by naltrexone (9 mg/kg i.p.), a mu-opioid receptor antagonist, and naltrindole (9 mg/kg i.p.), a delta-opioid receptor antagonist, respectively. 5 alpha,7 alpha-beta-(-)- N-methyl-N-[7-(1-pyrrolidinyl)-1-oxaspiro(4,5)dec-8-yl]benzene acetamide (U69593, 10 microM), a kappa-opioid receptor agonist, had no influence on the K(+)-evoked acetylcholine release. The findings suggest that both mu- and delta-opioid receptors might have a functional role in acetylcholine release from splanchnic nerve terminals in the adrenal medulla of the rat. The present study indicates that adrenal microdialysis is a useful method for studying the control mechanism of adrenomedullary function in the rat in vivo.

Histamine H1 receptor activation mediates the preferential release of adrenaline in the rat adrenal gland

Histamine elicited the release of catecholamines from "in vitro" perfused rat adrenals with an EC50 of 3 microM. This concentration was in the same range as those which caused a fall in the arterial blood pressure when infused intravenously in anaesthetized rats. Histamine stimulation was potently blocked by dexclorfeniramine (IC50 = 300 pM), but unaffected by ranitidine, suggesting the involvement of H1 receptors. Histamine release preferentially adrenaline. Mast cells were not detected within adrenal medulla by histochemical techniques. Compound 48/80 did not trigger catecholamine release. Catecholamine secretion evoked by splanchnic nerves stimulation was not modified by a combination of H1 and H2 antagonists. In conclusion, the histamine that elicited adrenaline release from rat adrenals comes from blood circulation not from local mast cells or splanchnic nerves. These effects are mediated through the activation of H1 receptors.

Distribution of immunoreactivity for enkephalin, substance P and vasoactive intestinal peptide in fibres surrounding splanchnic sympathetic preganglionic neurons in rats

The distribution of substance P, enkephalin and vasoactive intestinal peptide in fibres and cells was examined in the autonomic nuclei of the lower thoracic and lumbar segments of the rat spinal cord. Attention was focussed on the location of the peptides in sympathetic preganglionic neurons contributing to the greater and lesser splanchnic nerves and in fibres surrounding these neurons. To identify splanchnic preganglionic neurons, Fluoro-Gold was applied to the left splanchnic nerve in anaesthetized rats and some of these animals received intrathecal administration of colchicine at thoracic segments 6, 9 and 12, 24-48 h before perfusion with fixative. Immunoreactivity for substance P, enkephalin and vasoactive intestinal peptide in fibres and cells of the sixth thoracic to second lumbar spinal cord was detected with fluorescent immunocytochemical techniques. Most retrogradely labelled cells (90%) were located in the intermediolateral nucleus and the rest were situated in the nucleus intercalatus and the central autonomic nucleus of the gray matter. Terminals of fibres containing immunoreactivity to all three peptides were found in all autonomic regions. Fibres immunoreactive for substance P and enkephalin were seen projecting in the white matter to the region of the intermediolateral nucleus and extending from this nucleus to the central autonomic nucleus. Terminals containing each of the three peptides were also found surrounding the retrogradely labelled cells in the intermediolateral nucleus. Approximately two cells immunoreactive for vasoactive intestinal peptide were found per section and 80% were located in the autonomic regions. Fewer cells immunoreactive for substance P and enkephalin were observed (approximately one per section) and 70% were outside laminae VII and X. Although cells immunoreactive for substance P, enkephalin and vasoactive intestinal peptide were located in all autonomic regions of the spinal cord, cells doubly labelled with retrograde dye and with the antisera to either of the peptides could not be identified. The data suggest that (i) substance P, enkephalin and vasoactive intestinal peptide are contained in fibres of neurons regulating preganglionic sympathetic control of the abdominal viscera and its vasculature; and (ii) these peptides may not be major transmitters within splanchnic preganglionic neurons.

Changes in enkephalin immunoreactivity of sympathetic ganglia and digestive tract of the cat after splanchnic nerve ligation

The aim of the present study was to analyze changes in the enkephalin immunoreactivity of sympathetic prevertebral ganglia coeliac plexus and inferior mesenteric ganglion) and intestinal tract (myenteric plexus and external muscle layers) in cats 2 days after left thoracic splanchnic nerve ligation, using radioimmunoassay and immunohistochemical techniques. Specific polyclonal antibodies directed against methionine- and leucine-enkephalin were used. The nerve ligation led to a considerable increase in the enkephalin immunoreactivity in the cranial part of the ligated nerves. This finding confirms the presence, in the cat, of an enkephalin output originating from thoracic spinal structures which are probably enkephalin-containing preganglionic neurons. In prevertebral ganglia the nerve ligation induced a marked decrease in the enkephalin immunoreactivity, which was probably due to the interruption of thoracic enkephalin efferents projecting towards both the coeliac plexus and the inferior mesenteric ganglion. In the digestive tract, the nerve ligation depressed the methionine-enkephalin immunoreactivity only in the gastro-duodenal region, and had no effect on the ileo-colonic region. The results of the present study add to the growing evidence that the sympathetic nervous system is involved in regulating the enteric enkephalinergic innervation, which is probably involved in controlling the intestinal motility.

Decreased catecholamine secretion from the adrenal medullae of chronically diabetic BB-Wistar rats

Many humans with IDDM eventually lose the capacity to secrete epinephrine from their adrenal medullae. The mechanism for this pathological change is unknown. We hypothesized that this abnormality is attributable to neuropathic changes in the greater splanchnic nerves or in the chromaffin cells that they innervate. To study this hypothesis, we isolated rat adrenal glands, perfused them ex vivo, and measured the epinephrine content of the perfusate under various conditions of stimulation. We used transmural electrical stimulation (20-80 V, at 10 Hz) to induce epinephrine secretion indirectly by selectively activating residual splanchnic nerve terminals within the isolated glands. Under these conditions, epinephrine secretion was severely attenuated in glands from female BB-Wistar rats with diabetes of 4 mo duration compared with their age-matched, nondiabetic controls. These perfused diabetic adrenal medullae also demonstrated decreased catecholamine release in response to direct chromaffin cell depolarization with 20 mM K+, evidence that a functional alteration exists within the chromaffin cells themselves. Nonetheless, total catecholamine content of adrenal medullae from these diabetic rats was not significantly different from controls, indicating that the secretory defect was not simply attributable to a difference in the amount of catecholamines stored and available for release. Herein, we also provide histological evidence of degenerative changes within the cholinergic nerve terminals that innervate these glands.

Facilitatory role of the renin-angiotensin system in controlling adrenal catecholamine release in hemorrhaged dogs

Effects of the renin-angiotension system (RAS) on adrenal catecholamine release in response to hemorrhagic hypotension and splanchnic nerve stimulation (SNS) were studied in pentobarbital-anesthetized dogs. In hemorrhage experiments, mean blood pressure (MBP) was maintained at 50 mm Hg for 60 min by bleeding the arterial blood into a pressurized bottle. In the renal intact group (control), epinephrine (EPI) and norepinephrine (NE) output from the adrenal gland increased markedly during hemorrhagic hypotension: from 45 +/- 13 and 4.7 +/- 0.9 to 1,167 +/- 202 and 169 +/- 30 ng/min at 60 min after onset of hemorrhage, respectively. The increases in catecholamine output during hemorrhagic hypotension in the renal-intact group pretreated with captopril (1 mg/kg intravenously, i.v.) and in the renal-ligated group were significantly smaller than those in the control group. The increases in catecholamine output in the renal-ligated group infused with angiotensin II (AngII 10 ng/kg/min i.v.) were comparable to those in the control group. In SNS experiments, AngII infusion (10 ng/kg/min i.v.) enhanced increases in catecholamine output induced by 3 Hz SNS significantly. Captopril (1 mg/kg i.v.) did not affect the SNS-induced increases in catecholamine output. These results suggest that the renal RAS facilitates reflex release of adrenal catecholamines during hemorrhagic hypotension, at least in part, by acting directly on the release process of catecholamines from dog adrenal gland.

Release of endogenous noradrenaline from the vascularly perfused rat stomach in vitro: modulation by pre- and postsynaptic adrenoceptors

We developed an experimental in vitro model to detect a very small amount of endogenous noradrenaline (NA) released from the rat gastric sympathetic nerve terminals. The stomach was perfused via celiac artery with modified Krebs-Ringer solution containing 10 mM pargyline and 0.1% bovine serum albumin at a constant flow of 4 ml/min. The right greater splanchnic (SPL) nerve (preganglionic nerve of the gastric sympathetic nerve) was stimulated electrically with square-wave pulses of 2 msec duration and supramaximal intensity (5 mA) for 1 min. The rat stomach contained about 750 ng of NA and spontaneous overflow was about 0.05% of tissue content per 2 min. The NA overflow induced by SPL nerve stimulation at 5 Hz was abolished by tetrodotoxin (3 x 10(-7) M) and by Ca(++)-free medium containing 2 mM ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid. Hexamethonium (5 x 10(-4) M) significantly decreased the NA overflow induced by SPL nerve stimulation at 5 Hz. Yohimbine (10(-7) and 10(-6) M) and prazosin (10(-7) and 10(-6) M) dose-dependently enhanced the NA overflow induced by SPL nerve stimulation at 5 Hz. Clonidine (10(-7) and 10(-6) M) and methoxamine (10(-5) M) significantly decreased the NA overflow induced by SPL nerve stimulation at 1 Hz and this methoxamine-induced inhibition was abolished by 8-(p-sulfophenyl)-theophylline (5 x 10(-5) M).(ABSTRACT TRUNCATED AT 250 WORDS)

Skin-visceral divergent projection of cholecystokinin-containing dorsal root ganglion neurons: a tri-labelling study with fluorescent tracers and immunohistochemistry

Skin-visceral divergent projections of cholecystokinin (CCK)-containing dorsal root ganglion neurons were studied by combined technique of fluorescent double-labelling and immunohistochemistry. Fast blue (FB) and nuclear yellow (NY) were injected into the coeliac ganglion and the cutaneous branches of left 9th-11th intercostal nerves, respectively. Three kinds of neurons labelled with fluorescein were observed in T9-11 dorsal root ganglia: FB-labelled neurons with blue-fluorescent cytoplasm; NY-labelled neurons with yellow-fluorescent nucleus and double-labelled neurons with blue cytoplasm and yellow nucleus. The double-labelled neurons were found to account for 2.8% of total labelled neurons. The sections containing neurons labelled with fluorescein were stained by CCK-immunohistochemical procedure. Four kinds of neurons could be identified: NY-neurons with CCK-immunoreactivity (NY+CCK); FB-neurons with CCK-immunoreactivity (FB+CCK); NY+FB neurons with CCK-immunoreactivity (NY+FB+CCK); and neurons only CCK-positive. NY+FB+CCK tri-labelled neurons accounted for approximately 11.5% of NY+FB double-labelled neurons, and for 0.4% of all CCK-positive neurons. The findings clearly indicated that the peripheral processes of some sensory dorsal root ganglion neurons divergently project to both skin and visceral structure and contain CCK.

Functional aspects of calcium channels of splanchnic neurons and chromaffin cells of the rat adrenal medulla

Effects of the inorganic calcium channel blockers zinc, manganese, cadmium, and nickel on secretion of catecholamines from the perfused adrenal gland of the rat were investigated. Secretion of catecholamines evoked by splanchnic nerve stimulation (1 and 10 Hz) was not affected by nickel (100 microM), partially blocked (50%) by cadmium (100 microM), and almost completely blocked (90%) by zinc (1 mM) or manganese (2 mM). A combination of nickel and cadmium inhibited nerve stimulation-evoked secretion by 80-90%. Catecholamine secretion evoked by direct stimulation of chromaffin cells by acetylcholine (50 micrograms), nicotine (5 microM), muscarine (50 micrograms), and K+ (17.5 mM) was not blocked by either cadmium, nickel, or their combination. However, zinc and manganese almost abolished nicotine- and K(+)-evoked secretion of catecholamines. None of the above agents had any effect on the secretion evoked by muscarine. Acetylcholine-evoked secretion of catecholamines was only partially reduced (50%) by zinc and manganese. We draw the following conclusions from the above findings: (a) cadmium plus nickel selectively blocks the calcium channels of splanchnic neurons but has no effect on calcium channels of the chromaffin cells; (b) zinc and manganese do not discriminate between calcium channels of neurons and calcium channels of chromaffin cells; (c) partial inhibition of acetylcholine-evoked secretion by inorganic calcium channel blockers is consistent with the idea that activation of nicotinic receptors increases Ca2+ influx, and activation of muscarinic receptors mobilizes intracellularly bound Ca2+, which is not affected by calcium channel blockers.

Modulation by beta-adrenoceptors and angiotensin II receptors of splanchnic nerve evoked catecholamine release from the adrenal medulla

In the present study, we have evaluated the effect of both facilitatory beta 2-adrenoceptor and angiotensin II receptor on the release of adrenal catecholamines induced by electrical stimulation of the splanchnic nerve in anaesthetized and vagotomized dog. In these experiments, individual or combined treatments with the beta 2-adrenoceptor antagonist ICI 118551 (0.3 mg/kg i.v.), the converting enzyme inhibitor captopril (2 mg/kg i.v.), or the angiotensin II receptor antagonist saralasin (2 micrograms.kg-1.min-1 i.v.) were found to significantly decrease the release of adrenal catecholamines during splanchnic nerve stimulation (5-V pulses of 2 ms duration for 3 min at 1 Hz) whatever the order of administration of the drugs. On the other hand, the infusion of angiotensin II (20 ng.kg-1.min-1) was shown to potentiate the release of adrenal catecholamines in response to electrical stimulation, and this effect was totally blocked by treatment with saralasin (4 micrograms.kg-1.min-1 i.v.). This facilitating angiotensin mechanism differed from beta-adrenoceptor facilitating mechanism, since following beta-blockade with ICI 118551, angiotensin II infusion still significantly potentiated the release of catecholamines during splanchnic nerve stimulation. These observations thus suggest that both facilitating beta 2-adrenoceptors and angiotensin II receptors can independently modulate the release of adrenal catecholamines.

Substance P increases catecholamine secretion from perfused rat adrenal glands evoked by prolonged field stimulation

1. We have studied the effect of substance P (SP) on catecholamine (CA) secretion evoked by prolonged field stimulation from the perfused rat adrenal gland in vitro. 2. Previous studies show that SP has an inhibitory effect on the nicotinic response in a number of different tissue preparations. In the present study, we found that SP at concentrations from 10(-7) to 10(-6) M markedly increased CA secretion evoked by prolonged high-frequency field stimulation but not that evoked by low-frequency field stimulation. 3. In the absence of field stimulation SP by itself had no direct effect on CA secretion. This indicates that SP acts as a neuromodulator rather than a neurotransmitter to increase CA secretion from the adrenal medulla. 4. The nicotinic receptors were still functional following a period of prolonged field stimulation (120 min) because CA secretion was markedly increased in response to the nicotinic agonist dimethylphenylpiperazinium (DMPP). 5. Capsaicin pre-treatment reduced CA secretion evoked by prolonged field stimulation and the facilitatory action of SP on CA secretion lasted longer in these capsaicin-pre-treated rats than in controls, indicating that SP-containing capsaicin-sensitive fibres innervating the adrenal medulla may be involved in the regulation of CA secretion. 6. In parallel with the increase in CA secretion, 3H overflow from the splanchnic nerve pre-labelled with [3H]choline was also increased by SP. The increase in CA secretion by SP lasted longer than the increase in 3H overflow. These results suggest that SP facilitates CA secretion from the adrenal gland at two levels: (1) pre-synaptically by facilitating ACh release from splanchnic nerve terminals, and (2) post-synaptically by modulating the nicotinic secretory response by protection against nicotinic desensitization of secretion. 7. The present studies provide further evidence that endogenous SP in the splanchnic nerve may modulate CA secretion during stress.

Lack of release of vasoactive intestinal polypeptide and calcitonin gene-related peptide during electrical stimulation of enteric nerves in streptozotocin-diabetic rats

The simultaneous release of endogenous acetylcholine, serotonin, vasoactive intestinal polypeptide, substance P, and calcitonin gene-related peptide was measured during electrical field stimulation of isolated preparations of rat ileum from control and 8-wk streptozotocin-treated diabetic rats. Electrical field stimulation of the control rat ileum caused a significant increase in the release of all the above substances from the enteric nerves. The electrically evoked, but not the basal, release of these substances was inhibited by tetrodotoxin. In the diabetic rat ileum, however, there was no increase in the release of vasoactive intestinal polypeptide and calcitonin gene-related peptide during electrical stimulation, whereas endogenous release of acetylcholine, serotonin, and substance P was unaffected by the diabetic state. This was surprising in view of the increased fluorescence intensity and tissue content of vasoactive intestinal polypeptide-like immunoreactivity in the same tissue reported previously. The lack of increase in evoked release of vasoactive intestinal polypeptide in the diabetic preparations might be due to an impaired mechanism of release at the terminal site or to defective axonal transport of the peptide, whereas in the case of calcitonin gene-related peptide, it might be the result of the low level of the peptide present in the enteric nerve fibers of the diabetic rat ileum. The differential effect of diabetes on enteric nerves is discussed.

A study of the action of clonidine on secretion from the adrenal medulla in dogs

The effects of clonidine on adrenal catecholamine (adrenaline and noradrenaline) secretion were investigated in chloralose-anaesthetized dogs. Intravenous administration of clonidine (10 and 20 micrograms kg-1) induced a decrease in both adrenal catecholamine secretion rates and cardiovascular parameters (blood pressure and heart rate). In contrast, a dose of 5 micrograms kg-1 was ineffective. Intracisternal clonidine (in a lower dose of 3 micrograms kg-1) also decreased adrenaline and noradrenaline release from the adrenal gland. Clonidine failed to modify adrenal catecholamine release evoked by electrical stimulation of the splanchnic nerve. These results demonstrate that clonidine decreases adrenaline release from the adrenal gland through a central and not a peripheral mechanism in dogs. This action might contribute to its antihypertensive effects.

Intrinsic gamma aminobutyric acid receptors modulate the release of catecholamine from canine adrenal gland in situ

Immunohistochemical analysis documented the presence of gamma-aminobutyric acid (GABA)-containing fibers and GABA-containing chromaffin cells in canine adrenal glands. A dense network of fibers was visualized at the boundary between medullary and cortical cells, and, in the medullary tissue, GABA-containing fibers surrounded chromaffin cells. Some of these fibers enter the adrenal medulla together with splanchnic cholinergic nerves. The functional role of the GABAergic system in the regulation of catecholamine release from adrenal chromaffin cells was studied in canine adrenal glands in situ, using an autoperfusion system for the adrenal gland that was designed to eliminate indirect central effects of drugs or their metabolites on catecholamine release. The present study documents that GABA modulates the spontaneous release of catecholamines and the release elicited by electrical stimulation of the splanchnic nerve. GABAA receptor agonists such as THIP or muscimol increased the catecholamine content in adrenal effluent blood, whereas bicuculline (0.05 mmol/2 ml min-1), a GABAA receptor antagonist, reduced it. Baclofen (0.094 mmol/2 ml min-1), a GABAB receptor agonist, failed to alter the catecholamine content in adrenal effluent blood. The increased release of catecholamines elicited by 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3[2H]-one (THIP; 0.143 mmol/2 ml min-1) was prevented by bicuculline (0.05 mmol/2 ml min-1) but not by hexamethonium (2.48 mmol/2 ml min-1) or naloxone (0.122 mmol/2 ml min-1). Furthermore, denervation of the adrenal glands failed to prevent the THIP-elicited release of catecholamines.(ABSTRACT TRUNCATED AT 250 WORDS)

Met-enkephalin-Arg6-Gly7-Leu8 in large-cored vesicles of splanchnic nerve terminals innervating guinea pig adrenal chromaffin cells

Met-enkephalin-Arg6-Gly7-Leu8 (Met-Enk-Arg-Gly-Leu)-like immunoreactivity in the guinea pig adrenal medulla was investigated by the peroxidase-antiperoxidase method for light microscopy and by the protein A-gold method for electron microscopy. Because of a distinct Met-Enk-Arg-Gly-Leu-like immunoreactivity in the splanchnic nerve terminals innervating the chromaffin cell, their distribution and structure were clearly demonstrated. With electron microscopy, specific colloidal gold particles representing Met-Enk-Arg-Gly-Leu were localized in large-cored vesicles.

Somatostatin is present in a subpopulation of noradrenergic nerve fibres supplying the intestine

Somatostatin and dopamine beta-hydroxylase have been localized in the coeliaco-mesenteric ganglia, in mesenteric nerves and in the wall of the guinea-pig small intestine. Nerve lesions were used to determine the sources of the nerves. Nerve cell bodies in the coeliaco-mesenteric ganglia with immunoreactivity for both somatostatin and dopamine beta-hydroxylase project to the intestine via the mesenteric nerves. Most of their terminals are in the submucous ganglia, where they make up the full complement of noradrenergic terminals, and in the mucosa where other noradrenergic terminals, not containing somatostatin immunoreactivity, are also present. The small number of noradrenergic fibres present in the tertiary component of the myenteric plexus and in the circular muscle all show immunoreactivity for somatostatin. The noradrenergic fibres supplying the mesenteric and intestinal blood vessels and those ramifying in the myenteric ganglia do not contain somatostatin. The numerous somatostatin-immunoreactive nerves in the enteric plexuses that do not contain dopamine beta-hydroxylase come from enteric nerve cell bodies. These results, considered in the context of other published work, indicate that post-ganglionic sympathetic noradrenergic neurons are chemically coded according to the target tissue they supply and suggest that neurons that were hitherto thought to be neurochemically equivalent, but which serve different functions, are in fact chemically distinct.

The distribution of vasoactive intestinal peptide in the rat adrenal cortex and medulla

There is increasing evidence for the role of the autonomic nervous system in the control of adrenal cortical function although the nature of the innervation is as yet unknown. In view of our expanding knowledge of the roles which peptidergic putative transmitters play in the autonomic nervous system, the present study was adrenal gland. Using immunocytochemical methods, VIP was found distributed in fibers in the adrenal cortex and medulla. VIP fibers were found primarily in the capsule and zona glomerulosa of the cortex and in small bundles in the medulla and appeared to innervate the parenchymal cells in both cases. Both colchicine pretreatment and ligation of the splanchnic nerve resulted in an increase in staining of fibers of the cortex and the medulla. Demedullated adrenals (regenerated) exhibited a reduced number of VIP fibers in the zona glomerulosa. It appears that the medullary and at least part of the cortical VIP fibers originate in the medullary VIP cell bodies which are regulated by the splanchnic nerve. The distribution of VIP suggests an important role for this peptide in both adrenal cortical and medullary function and a possible medullary modulation of adrenal cortical function.

[Composition of the polypeptides participating in orthograde axonal transport in the nerve elements of the caudal mesenteric ganglion of the cat]

Composition of the polypeptides translocated by the axonal transport in the lumbar splanchnic and hypogastric nerves before and after total section of these nerves was studied in the model of the inferior mesenteric ganglion with pre- and postganglionic nerve trunks. The data obtained suggest presence of the orthograde axonal transport of specific proteins associated with the nerve fibre growth along the axons of afferent neurons whose bodies are localized in the inferior mesenteric ganglion, as well as along efferent fibres with trophic centers situated in the ganglion. Axonal transport of the polypeptide with molecular weight 29.000 Dalton unidentified in other nerve structures was shown to occur along the afferent fibers.

Starvation in man

Starvation entails a progressive selection of fat as body fuel. Soon after a meal glucose utilisation by muscle ceases and fatty acids are used instead. Ketoacid levels in blood become elevated over the first week, and the brain preferentially uses these instead of glucose. The net effect is to spare protein even further, as glucose utilisation by brain is diminished. Nevertheless, there is still net negative nitrogen balance, but this can be nullified by amino acid or protein supplementation. Insulin appears to be the principal regulatory hormone. Recent data suggest that decreased levels of active T3 may play a role by sparing otherwise obligated calories by decreasing metabolic needs.

Phenylethanolamine-N-methyl transferase (PNMT) activity and catecholamine content in chromaffin tissue and sympathetic neurons in the cod, Gadus morhua

The activity of phenylethanolamine-N-methyl transferase (PNMT) has been measured in the chromaffin tissue of the head kidney and in the sympathetic neurons of the coeliac ganglion/splanchnic nerve in the cod. The content of adrenaline and noradrenaline in these tissues and in other adrenergically innervated tissues and blood plasma was also determined. Adrenaline dominates over noradrenaline in most sympathetically innervated tissues, in the chromaffin tissue and in blood plasma, but not in the muscularis mucosae of the swimbladder. High PNMT activity was found in the chromaffin tissue in the walls of the posterior cardinal veins, and also in sympathetic neurons. It is concluded that the adrenaline found in the sympathetic nerves may originate from intraneuronal adrenaline synthesis, but also from circulating adrenaline which is taken up and stored.

Release of acetylcholinesterase into the perfusate from the ox adrenal gland

Increasing the potassium ion concentration of Tyrode’s solution perfusing an isolated ox adrenal gland leads to a release of acetylcholinesterase activity into the perfusate. The amount of enzyme activity released by added potassium is much reduced if calcium ions are omitted from the perfusion fluid. The activity of acetylcholinesterase secreted into the perfusate was confined to a single isoenzyme which is identical with the only soluble isoenzyme present in splanchnic nerve trunks and with one of the five soluble isoenzymes in the adrenal medulla.

Splanchnic oxygen uptake in relation to systemic oxygen uptake during postoperative splanchnic blockade and postoperative fentanyl analgesia

In 34 patients with gallbladder disease, but otherwise healthy, the systemic and splanchnic oxygen uptake were studied in connection with cholecystectomy. Postoperatively, 22 patients were given a posterior splanchnic blockade with 0.5% plain lidocaine, and 12 were given fentanyl intramuscularly in a dose of 3.5 mug/kg b.w. Postoperatively, before the analgesic agent was administered, both the systemic and splanchnic oxygen uptake were increased by 40--50%, the splanchnic fraction of the systemic oxygen uptake being the same as preoperatively. Following administration of fentanyl, as well as after splanchnic blockade, the systemic oxygen uptake decreased almost to the preoperative level. The splanchnic oxygen uptake, however, did not change after fentanyl administration but increased further significantly following splanchnic blockade. The splanchnic fraction of the systemic oxygen uptake increased rapidly after the blockade, while it increased slowly after fentanyl administration.

Effects of abdominal surgery under general anaesthesia and of postoperative analgesic therapy on splanchnic exchange of some blood borne energy metabolites

Sixteen patients with gallbladder disease, but otherwise healthy, were studied in connection with cholecystectomy. For postoperative analgesia, seven patients were given a posterior splanchnic blockade, 30 ml of 0.5% plain lidocaine, and nine patients were given fentanyl intramuscularly in a dose of 3.5 mug/kg b.w. Immediately after the operation and before analgesia, the arterial blood concentrations of glucose, lactate, glycerol, 3-hydroxybutyrate, and free fatty acids increased significantly. The splanchnic exchange of these metabolites was also significantly increased, except for glucose, the splanchnic release of which was significantly reduced. Induction of analgesia, both methods, was followed by a rapid significant decrease of the arterial blood concentration of glycerol, which tended to rise later when the analgesia disappeared. The arterial blood concentration of glucose and lactate showed a tendency to decrease slowly following both kinds of analgesia, while the arterial blood concentration of 3-hydroxybutyrate remained stable. The splanchnic release of glucose was significantly reduced after administration of fentanyl, while it increased significantly following splanchnic blockade, the splanchnic glucose release being correlated to arterial blood pH. The splanchnic release of 3-hydroxybutyrate was significantly reduced during maximal analgesia in both groups. The splanchnic uptakes of glycerol and free fatty acids were correlated to their splanchnic inflows.