L. Bauce

Role for the submandibular gland in modulating pulmonary inflammation following induction of systemic anaphylaxis

Previous studies have shown that bilateral decentralization of the superior cervical ganglia (SCG; decentralization) attenuates allergen-induced pulmonary inflammatory responses in male rats sensitized to the nematode Nippostrongylus brasiliensis. The present report examines the neuronal and glandular mechanisms mediating the protection against pulmonary inflammation afforded by decentralization. Tissues and organs innervated by the SCG are responsible for this protection since, in a manner similar to decentralization, bilateral removal of the SCG (ganglionectomy) reduced anaphylaxis-induced accumulation of inflammatory cells in bronchoalveolar lavage fluid. Removal of the submandibular gland (sialadenectomy) did not modify the severity of the pulmonary inflammation, but concurrent sialadenectomy and decentralization abolished the protective effect of decentralization. Thus, we postulate that cervical sympathetic nerves tonically inhibit release of anti-inflammatory factors from submandibular glands. No relationship was found between noradrenaline and serotonin content of submandibular glands and the degree of protection against pulmonary inflammation offered by decentralization and ganglionectomy. Both decentralization and ganglionectomy appeared to increase the level of transcripts that encode immunomodulatory growth factors (nerve growth factor and epidermal growth factor) in submandibular glands, but these denervations evidently did not modify the transcripts for TGF beta 2. Systemic inflammatory events are regulated by the central nervous system at a level superior to the SCG probably through modulation of immunoregulatory factors in submandibular glands.

Microdialysis with high NaCl causes central release of amino acids and dopamine.

Abstract: Recent studies have shown that the neuropeptides arginine‐8‐vasopressin (AVP) and oxytocin (OXT) are released within the supraoptic (SON) and paraventricular (PVN) nuclei of the hypothalamus in response to microdialysis of these nuclei with high‐NaCl perfusion media. These results suggest an inherent osmosensitivity of SON and PVN neurons. To investigate whether the observed release of AVP/OXT is a unique phenomenon to these neuropeptides, several brain regions were examined for the release of amino acids or dopamine in response to high‐ or low‐NaCl stimulation. Urethane‐anesthetized male Sprague‐Dawley rats were perfused with five‐ion solution using U‐shaped microdialysis probes. Samples were collected at 30‐min intervals and analyzed for amino acids and dopamine by HPLC. In the dialysates of all perfusion areas, including the SON, PVN, hippocampus, and striatum, concentrations of Asp, Glu, Ser, Gln, Gly, taurine (Tau), and γ‐aminobutyric acid (GABA) were significantly increased during perfusion with high‐NaCl medium. This release was found to be dose dependent when tested in the hippocampus and striatum with perfusion medium containing 0.5 or 1.0 M NaCl. However, only the release of Glu and Ser was found to be Ca2+ dependent. In contrast, the use of mannitol, a nonionic osmolyte, for perfusions in the striatum in concentrations of 0.5 and 1 M resulted in reduced levels of amino acids in the dialysates (Glu, Ser, Gln, and Tau). Low‐NaCl perfusion medium (0.01 M) resulted in significantly increased Glu, Tau, Gly, and GABA levels in the striatum. In addition, dopamine levels in striatal dialysates were significantly increased during stimulation with 1 M NaCl. These results indicate that stimulation with high NaCl concentrations affects the release of several neurotransmitters and is not specific for AVP and OXT. The described phenomenon of the release of amino acids in response to this stimulation seems to be a response to the changed ionic concentration rather than to the osmolality. In light of these findings shown for amino acids and dopamine as well as those previously reported for AVP, OXT, and angiotensin, it would appear that sensitivity to tonicity changes brought about by microdialysis may be a feature of many transmitter systems.

The effects of intrathecal administration of arginine-vasopressin and substance P on blood pressure and adrenal secretion of epinephrine in rats

The effects of intrathecally administered arginine-vasopressin (AVP) and substance P (SP) on adrenal medullary secretion of epinephrine were examined in anesthetized Sprague-Dawley rats. Plasma epinephrine levels were measured in blood samples taken directly from the adrenal vein using a novel micropuncture technique. The blood samples (20-30 microliter in volume) were taken before, and 2 min, 15 min and 30 min after intrathecal injections of AVP, SP or vehicle only. Plasma was assayed for epinephrine using high pressure liquid chromatography. Adrenal venous epinephrine levels were not significantly altered by the intrathecal administration of AVP, thereby suggesting that adrenal epinephrine secretion is not involved in the cardiovascular responses previously reported to occur following similar doses of intrathecal AVP. Intrathecal SP administration, while causing blood pressure responses similar to those produced by AVP, resulted in significant increases in adrenal vein epinephrine. This finding suggests that activation of adrenal secretion of epinephrine may contribute to SP-initiated blood pressure changes.

Alcohol dependence and withdrawal in the rat: An effective means of induction and assessment

Numerous problems have been associated with previous attempts to develop a suitable method for the induction and assessment of alcohol dependence and withdrawal syndrome in the rat. Using our modification of a common inhalation method for the long-term administration of ethanol, these problems can be eliminated. Adult male rats (Long Evans and Brattleboro) were exposed to ethanol vapor concentrations of 7 to 35 mg/liter of air, which cause rapid development of tolerance and physical dependence. With this inhalation method, it is possible to obtain and easily maintain high levels of ethanol in the blood (150 to 400 mg/dl). When exposure to ethanol is terminated, ethanol is eliminated from the system within 1 to 6 hr. This rapid elimination of ethanol is accompanied by a high susceptibility to withdrawal reactions. The severity of the withdrawal syndrome was assessed within 6 to 24 hr after cessation of the ethanol administration by exposing each rat individually to a 60 to 120-sec period of bell ringing. Convulsive seizures were observed in nearly 90% of the animals tested, with a mortality rate of less than 20%.

Secretion and serotonin release in the isolated rat lacrimal gland : the effects of substance P and calcitonin gene-related peptide

A close anatomical relationship between nerves containing substance P and calcitonin gene-related peptide (CGRP) and mast cells containing serotonin has been demonstrated in the rat lacrimal gland. This study investigates the potential for peptidergic regulation of lacrimal mast cells by examining the actions of substance P, CGRP and serotonin on protein and peroxidase secretion from isolated lacrimal segments and on substance P and CGRP to release serotonin from the lacrimal mast cells. Substance P, CGRP and serotonin evoked marked increases in total protein and peroxidase from the lacrimal. Sodium cromoglycate, a mast cell stabilizer, significantly reduced or blocked the secretory responses elicited by these agonists. Chromatographic analysis using electrochemical detection revealed that substance P, but not CGRP, augmented the release of serotonin from the gland. The substance P evoked peroxidase secretion and serotonin release was blocked by CGRP and by sodium cromoglycate. These results support a role for mast cells in the regulation of lacrimal secretion and suggest a novel regulatory interaction between substance P and CGRP in the control of lacrimal function through a neuro-immune interaction.

Plasma catecholamines in conscious rabbits after central administration of vasopressin

Arterial levels of epinephrine (E) were significantly raised for all times sampled, after intracerebroventricular (i.c.v.) injection of arginine vasopressin (AVP) (1 nmol) into conscious rabbits. Venous levels of norepinephrine (NE) were significantly raised within the first 4 min after a similar i.c.v. injection of AVP. The significant increases in arterial E and venous NE correspond in time and therefore could account for changes in heart rate and blood pressure elicited by centrally injected AVP. Therefore, AVP could influence cardiovascular function by increasing the activity of the sympatho-adrenomedullary system.

I. Determination of the endogenous and evoked release of catecholamines from the hypothalamus and caudate nucleus of the conscious and unrestrained rat

The action of catecholamines within the CNS is important for the expression of numerous vegetative and behavioral functions. To understand the role these amines play, it is necessary to measure changes in the levels of these transmitter substances by utilizing new developments and methodology in the behaving animal. Utilizing new developments in methodology, it is possible to measure the release of amines into perfusates obtained from specific sites in the brain of the rat under basal and evoked conditions without prior purification or concentration. Using the push-pull perfusion technique, perfusates were obtained from the hypothalamus and caudate nucleus and analyzed by liquid chromatography with electrochemical detection. It is possible to readily determine basal release of dopamine from the caudate nucleus. Detection of both dopamine and noradrenaline is possible under ephedrine stimulated conditions from both the caudate nucleus and the hypothalamus. Although levels of serotonin (5-HT) were detected in brain perfusates, it may not be of neuronal origin. It may be possible to use these techniques to delineate the roles these amines play in various physiological functions.

Kainate evokes the release of endogenous glycine from striatal neurons in primary culture

The actions of 56 mM KCl and excitatory amino acid (EAA) agonists on the release of endogenous glycine (Gly) from striatal neurons in primary culture was examined. During a 3 min period, 2 x 10(6) striatal neurons released 743 +/- 51 pmol of Gly. In the presence of 56 mM KCl, an additional 492 +/- 52 pmol of Gly (+66%) were released, 75% of which was dependent upon the presence of extracellular calcium. When striatal neurons were exposed to 1 mM N-methyl-D-aspartate (NMDA) or quisqualate (QA), endogenous Gly released was increased by 370 +/- 71 (+50%) or 120 +/- 31 (+16%) pmol, respectively. In the presence of 1 mM kainate (KA), however, the release of endogenous Gly increased by 994 +/- 82 pmol (+135%). Interestingly, while KA (1 mM) was twice as effective as KCl (56 mM) in evoking the release of endogenous Gly, KCl was 5 times more effective than KA in evoking the release of endogenous gamma-aminobutyric acid (GABA). KA-induced increases of endogenously released Gly were dose-dependent (EC50, 100 microM), saturable and not significantly reduced in the absence of extracellular calcium. The actions of KA were blocked by coincubation with 6-cyano-2,3-dihydroxy-7-nitro-quinoxaline (CNQX), a competitive antagonist at the KA receptor. These data suggest that the release of endogenous Gly from striatal neurons in primary culture is regulated principally by EAA actions at the KA receptor system.

Depletion of central catecholamines reduces pressor responses to arginine vasopressin

Previous reports that central administration of arginine vasopressin (AVP) increases turnover of brain catecholamines raise the possibility that the pressor responses which follow central administration of AVP may be mediated, in part, by central catecholamines. To test this hypothesis, rats were given intraventricular injections of vehicle, or of the neurotoxin, 6-hydroxydopamine, which resulted in significant depletions of hypothalamic and medulla oblongata noradrenalin and hypothalamic dopamine, but not of medullary dopamine or of hypothalamic and medullary 5-hydroxytryptamine. Following a one week recovery, these conscious rats, fitted with indwelling arterial catheters, were given intraventricular injections of AVP; the increases in arterial pressure and heart rate were significantly reduced in the catecholamine-depleted animals. These data support the hypothesis that the pressor and tachycardia responses to intraventricular AVP are mediated, in part, by central catecholamine-containing neurons.

A method for continuous blood sampling during cold water immersion

A technique, consisting of a pre-calibrated, catheter-peristaltic pump combination, for continuous blood sampling was tested using six volunteers during a 20 min immersion in cold water at 14.7 +/- 0.9 degrees C. The device offered the advantage of continued collection of blood samples from an antecubital vein during the experiment with little discomfort for the subjects and in sufficient volume for assay of plasma constituents eg. catecholamines.