bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of sleep deprivation in neonatal rats
Authors: Frank Marcos G. , Morrissette Roger , Heller H. Craig
Published: December 2017

This investigation represents the first systematic study of sleep homeostasis in developing mammals that spans the preweaning and postweaning periods. Neonatal rats from 12 to 24 days of postnatal life ( P12– P24) were anesthetized with Metofane (methoxyflurane) and implanted with miniaturized electroencephalographic (EEG) and electromyographic electrodes. After 48 h of recovery, neonatal rats were sleep deprived for 3 h by either gentle handling or forced locomotion. We find that 3-h sleep deprivation produces dramatically different compensatory responses at different stages of postnatal development. In striking contrast to adult rats, sleep deprivation does not increase slow-wave sleep EEG delta (0.5–4.0 Hz) activity in rats younger than P24. However, P12– P20rats do show evidence of sleep regulation because they show compensatory increases in sleep time and sleep continuity during recovery. In P12 rats, ∼90% of total slow wave sleep time lost during the sleep-deprivation period was recovered during subsequent sleep. A similar recovery of active sleep time was observed in P20– P24rats. These findings suggest not only that sleep is regulated in neonatal rats but that the accumulation and/or discharge of sleep need changes dramatically between the third and fourth postnatal weeks.
ETAreceptor blockade attenuates the hypertension but not renal dysfunction in DOCA-salt rats
Authors: Allcock Graham H. , Venema Richard C. , Pollock David M.
Published: December 2017

Endothelin (ET)-1 has potent renal and systemic vasoconstrictor properties, and thus we investigated whether ET-1 plays a role in increasing blood pressure and decreasing renal function in DOCA-salt hypertension. After a right nephrectomy, rats had DOCA or placebo pellets implanted subcutaneously and were given saline or tap water to drink, respectively. Additional groups of rats were given the ETAreceptor antagonist A-127722 in their water. Rats were maintained in metabolic cages for monitoring excretory function and food and water intake. Three weeks after surgery, mean arterial pressure (MAP) was recorded in the conscious rats via a carotid artery catheter. As expected, DOCA-salt rats had significantly higher MAP compared with uninephrectomized controls (197 ± 6 vs. 133 ± 3 mmHg). Creatinine clearance, used as an estimate of glomerular filtration rate, was significantly reduced in DOCA-salt rats (2.9 ± 0.4 vs. 6.8 ± 0.3 dl ⋅ day−1⋅ 100 g−1body wt in controls). ETAreceptor blockade with A-127722 significantly reduced MAP (156 ± 8 mmHg) but had no effect on creatinine clearance of DOCA-salt-treated rats (2.8 ± 0.3 dl ⋅ day−1⋅ 100 g−1body wt). Plasma ET-1 levels were significantly raised after DOCA-salt treatment (1.4 ± 0.5 pg/ml vs. 0.4 ± 0.1 pg/ml in controls). A-127722 treatment increased circulating ET-1 levels in both placebo (2.3 ± 0.5 pg/ml) and DOCA-salt (5.6 ± 0.7 pg/ml) rats. However, ET-1 mRNA expression in renal cortical and medullary tissue was not affected by either A-127722 or DOCA-salt treatments. Thus ETAreceptors appear to play a role in the maintenance and development of DOCA-salt hypertension but not in the accompanying reduction of renal function.
Pharmacological characterization of ATP receptors in ampulla from frog semicircular canal
Authors: Butlen Daniel , Bernard Christian , Ferrary Evelyne
Published: December 2017

Phosphoinositidase C activities sensitive to purine and pyrimidine nucleotides have been identified earlier in ampulla from Rana ridibunda semicircular canal. The aim of this study was to characterize the pharmacological properties of other P2receptors borne by this structure. A microassay was developed to measure the binding of [35S]adenosine 5′- O-(2-thiodiphosphate) ([35S]ADPβS) to a few ampullas microdissected from frog semicircular canals. When determined at 4°C in the absence of divalent cations, [35S]ADPβS binding was saturable with incubation time and reversible after elimination of free radioligand. The dissociation kinetics were biphasic and comprised a major component that was rapidly reversible and a minor component that dissociated slowly. [35S]ADPβS binding was competitively inhibited by unlabeled ADPβS with an apparent dissociation constant of 0.48 ± 0.09 μM and a Hill coefficient of 0.70 ± 0.06, and Scatchard analysis revealed a minor class of high-affinity binding sites (RT1= 52 ± 11 fmol [35S]ADPβS bound/ampulla and Kd1= 0.15 ± 0.04 μM) and a major class of low-affinity binding sites (RT2= 436 ± 79 fmol [35S]ADPβS bound/ampulla and Kd2= 2.0 ± 0.8 μM). The pattern of stereospecificity for recognition of unlabeled structural ATP analogs was ADPβS ≥ α,β-methyleneadenosine 5′-triphosphate = ADP = adenosine 5′- O-(3-thiotriphosphate) > ATP = diadenosine tetraphosphate = AMP > 2′- and 3′- O-(4-benzoylbenzoyl)-adenosine 5′-triphosphate ≥ 2-methylthioadenosine 5′-triphosphate > 2-desoxythymidine 5′-triphosphate = guanosine 5′-triphosphate = inosine-5′-triphosphate = xanthosine 5′-triphosphate = cytosine 5′-triphosphate = uridine 5′-triphosphate = uridine-5′-diphosphate, whereas cAMP and adenosine were devoid of activity. For antagonists, suramin revealed competitive inhibitor potencies, whereas reactive blue 2 and DIDS acted as pure noncompetitive inhibitors. Results suggest that the population of labeled receptors is heterogeneous and contains a low number of P2Y-like receptors and a large number of P2X-like receptors whose molecular subtypes and functions in endolymph homeostasis remain to be defined.
Role of paraventricular nucleus parvicellular neurons in the compensatory responses to graded hemorrhage
Authors: Blair M. L. , Want A. , Olschowka J. A. , Piekut D.
Published: December 2017

The goal of this study was to determine the role of the parvicellular component of the paraventricular hypothalamic nucleus (PVH) in the compensatory responses to blood loss. Male Sprague-Dawley rats were prepared with bilateral ibotenate lesions of the parvicellular PVH (PVHx; n = 5) or with sham lesions (Sham; n = 8). After >10 days recovery, hemorrhage was performed by gradual withdrawal of 16 ml/kg blood over 34 min via an indwelling femoral arterial catheter while the rats were conscious and unrestrained. Basal serum corticosterone levels, plasma renin concentration (PRC), mean arterial pressure, and heart rate did not differ between PVHx and Sham, whereas basal hematocrit was lower in PVHx than Sham (40 ± 1 vs. 44 ± 1; P < 0.05). After hemorrhage, corticosterone increased fourfold in Sham ( P < 0.001) but did not increase significantly in PVHx. However, the blood pressure, heart rate, PRC, and hemodilution responses to hemorrhage were the same in Sham and PVHx during both the normotensive (7–13 ml/kg blood loss) and hypotensive (16 ml/kg blood loss) phases. In conclusion, the parvicellular PVH is essential for the corticosterone response, but not for the cardiovascular or renin responses to blood loss.
Reduction of NMDA receptor activity in cerebrocortex of turtles (Chrysemys picta) during 6 wk of anoxia
Authors: Bickler P. E. ,   (With the Technical Assistance of N. Verma)
Published: December 2017

Survival of brain anoxia during months of winter dormancy by the Western painted turtle, Chrysemys picta, may rely on inactivation of neuronal ion channels. During 2 h of anoxia, Ca2+influx via the N-methyl-d-aspartate (NMDA) subtype of glutamate receptor decreases 30–40%, but it is not known if prolonged anoxic dormancy is associated with even more profound downregulation of this important channel. Because ionized Ca2+in cerebrospinal fluid (CSF) increases five- to sixfold during prolonged anoxia, the potential for uncontrolled Ca2+influx and neurotoxicity is increased. To study the regulation of NMDA receptor activity, we measured NMDA-mediated changes in intracellular Ca2+(NMDA-ΔCa2+) in turtle cerebrocortical sheets with fura 2. Turtles were kept in N2-bubbled aquariums for 2 h to 6 wk at 2–3°C. NMDA-ΔCa2+decreased 60 ± 14% ( P < 0.05) after 2 h of anoxia and did not decrease further for 6 wk. Intracellular Ca2+increased from 135 to 183 nM ( P < 0.05) after 3 wk of anoxia and thereafter returned toward preanoxic levels. When NMDA receptor activity was assessed in artificial CSF containing the ions found in anoxic brain CSF (pH 7.25, 69 mM lactate, 8.4 mM Ca2+, and 5.1 mM Mg2+), NMDA-ΔCa2+was twice control initially but was 21% less than in normoxic artificial CSF after the end of 6 wk, suggesting altered sensitivity of the NMDA receptor to ionized Ca2+during prolonged anoxia. Regulation of NMDA receptor activity in turtle cerebrocortex during 6 wk of anoxia thus results in depression of NMDA receptor Ca2+flux, despite a sixfold increase in ionized extracellular Ca2+.
Inhibition of renal arachidonic acid ω-hydroxylase activity with ABT reduces blood pressure in the SHR
Authors: Su Ping , Kaushal K. Maya , Kroetz Deanna L.
Published: December 2017

The mechanism-based cytochrome P-450 (CYP) inhibitor 1-aminobenzotriazole (ABT) was characterized as an inhibitor of renal arachidonic acid metabolism and administered to spontaneously hypertensive rats (SHRs) to determine the effect of reduced eicosanoid production on mean arterial pressure (MAP). A single intraperitoneal dose of ABT to Sprague-Dawley rats caused a dose-dependent loss of renal CYP content, arachidonic acid metabolism, and CYP4A protein. In the cortex and outer medulla, ABT showed a high degree of selectivity for the CYP4A enzymes, reflected by the potent inhibition of 19- and 20-hydroxyeicosatetraenoic acid (19- and 20-HETE) formation. A 50 mg/kg dose of ABT reduced cortical 20-HETE formation to 16.1 ± 0.82% of control and outer medullary 20-HETE formation to 23.8 ± 0.45% of control. In contrast, there was no inhibition of renal epoxygenase activity at this dose. Renal CYP content, arachidonic acid ω- and (ω-1)-hydroxylase activity, and CYP4A protein levels gradually return to control levels by 72 h after a single dose of ABT. Cortical 20-HETE formation recovered from 17.9 ± 3.15% of control at 6 h to 84.8 ± 4.67% of control at 72 h after ABT administration. A single injection of ABT to 7-wk-old SHRs caused an acute reduction in MAP, which remained suppressed for at least 12 h. The effect was maximal within 4 h and averaged 17–23 mmHg during the 4- to 12-h period after administration. 20-HETE formation was inhibited 85% in the cortex and 70–80% in the outer medulla during the period when MAP was reduced. A structurally related ABT analog 1-hydroxybenzotriazole had no effect on blood pressure or renal arachidonic acid metabolism. These results identify ABT as a selective inhibitor of renal CYP4A activity and provide further support for a role for 20-HETE in the regulation of blood pressure.
Regulation of jejunal sodium and water absorption by angiotensin subtype receptors
Authors: Jin Xiao-Hong , Wang Zhi-Qin , Siragy Helmy M. , Guerrant Richard L. , Carey Robert M.
Published: December 2017

The purpose of this study was to determine the precise role of angiotensin subtype-1 (AT1) and -2 (AT2) receptors and the mechanisms by which they act to alter fluid transport in the rat jejunum. In rats on normal sodium intake, ANG II at low dose stimulated net jejunal fluid absorption, whereas at a high dose the peptide inhibited absorption. Low-dose ANG II-stimulated fluid absorption was blocked completely by the specific AT2receptor antagonist PD-123319 (PD) but was unchanged by the AT1receptor antagonist losartan (Los). The AT2receptor agonist CGP-42112A, caused an inversely dose-dependent increase in fluid absorption, which also was totally prevented by PD but was unaltered by Los. Conversely, high-dose ANG II inhibition of absorption was blocked by Los but not by PD. In animals receiving normal sodium intake, neither Los nor PD alone altered fluid absorption. In sodium-restricted animals, however, Los alone increased absorption and PD alone inhibited absorption. In rats on normal sodium intake, low-dose ANG II increased jejunal interstitial and luminal (loop) fluid concentrations of cGMP. These increases in cGMP were blocked with PD but not with Los. 8-Bromoguanosine-3′,5′-cyclic monophosphate administered via the mesenteric artery or the submucosal interstitial space markedly increased absorption, but it inhibited absorption when administered into the loop. High-dose ANG II decreased jejunal interstitial and loop fluid cAMP and increased PGE2. The increase in PGE2was blocked by Los but not by PD. The data demonstrate that ANG II mediates jejunal sodium and water absorption by an action at the AT2receptor involving cGMP formation. The data also show that ANG II inhibits absorption via the AT1receptor by a mechanism that is both negatively coupled to cAMP and increases jejunal PGE2production.
Effects of adrenalectomy and subsequent corticosterone replacement on rat sleep state and EEG power spectra
Authors: Bradbury Margaret J. , Dement William C. , Edgar Dale M.
Published: December 2017

Individual effects of corticotropin-releasing hormone (CRH) and glucocorticoids on sleep have been difficult to discern due to the feedback effects each hormone exerts on the other. In addition, it is not known whether hypothalamic-pituitary-adrenal axis hormones alter sleep homeostasis or circadian influences on sleep propensity. We therefore analyzed sleep architecture and electroencephalographic (EEG) power in freely moving rats before and after removal of corticosterone (thus elevating endogenous CRH) by surgical adrenalectomy. Adrenalectomy reduced the amplitude of the diurnal rhythms of maximal and average sleep bout lengths ( P < 0.004). After adrenalectomy, power from 1 to 4 Hz decreased ( P < 0.042), whereas power from 9 to 12 Hz increased in the power spectra of the EEG recording ( P = 0.001). Administration of physiological corticosterone replacement reversed some of these effects. Supraphysiological corticosterone replacement in adrenalectomized rats reduced the amount of non-rapid-eye-movement sleep in the 24-h cycle ( P = 0.001). During each endocrine condition, rats were sleep deprived for 6 h. Endocrine status did not alter the subsequent homeostatic response to sleep deprivation. Thus ADX and supraphysiological corticosteroid replacement each altered sleep architecture without a demonstrable effect on sleep homeostasis.
Brain cytokine mRNAs in anorectic rats bearing prostate adenocarcinoma tumor cells
Authors: Plata-Salamán Carlos R. , Ilyin Sergey E. , Gayle Dave
Published: December 2017

Cancer is consistently associated with anorexia. The Lobund-Wistar rat model of prostate cancer exhibits clinical manifestations (including anorexia) that resemble many aspects of the human disease. Cytokines are proposed to be involved in cancer-associated anorexia. Here we investigated mRNA profiles of feeding-modulatory cytokines and neuropeptides in specific brain regions of anorectic Lobund-Wistar rats bearing prostate adenocarcinoma tumor cells. Interleukin (IL)-1β system components (ligand, signaling receptor, receptor accessory proteins, receptor antagonist), tumor necrosis factor-α, transforming growth factor-β1, glycoprotein 130 (IL-6 receptor signal transducer), proopiomelanocortin (POMC, opioid peptide precursor), and neuropeptide Y (NPY) mRNAs were analyzed with sensitive and specific RNase protection assays. The same brain region sample was assayed for all components. The data show that early anorexia in tumor-bearing rats was associated with an upregulation of IL-1β mRNA in the brain regions examined (cerebellum, cortex, and hypothalamus). IL-1 receptor antagonist (IL-1Ra) mRNA and IL-1 receptor type I mRNA levels were also significantly increased in the cortex and hypothalamus. All other cytokine components, POMC, or NPY mRNA levels were not significantly different between tumor-bearing and pair-fed (control) rats. IL-1β mRNA and IL-1Ra mRNA were also significantly upregulated in the spleen of tumor-bearing rats. These data suggest that 1) IL-1β mRNA upregulation in the brain may be relevant to the anorexia exhibited by the tumor-bearing Lobund-Wistar rat and 2) in vivo characterization of cytokine components in discrete brain regions during cancer is necessary to understand underlying molecular mechanisms responsible for cancer-associated neurological manifestations.
Liposomal VIP attenuates phenylephrine- and ANG II-induced vasoconstriction in vivo
Authors: Ikezaki Hiroyuki , Önyüksel Hayat , Rubinstein Israel
Published: December 2017

The purpose of this study was to determine whether vasoactive intestinal peptide (VIP) modulates vasoconstriction elicited by phenylephrine and ANG II in vivo and, if so, to begin to elucidate the mechanisms underlying this phenomenon. Using intravital microscopy, we found that suffusion of phenylephrine and ANG II elicits significant vasoconstriction in the in situ hamster cheek pouch that is potentiated by VIP-(10—28), a VIP receptor antagonist, but not by VIP-(1—12) ( P< 0.05). Aqueous VIP has no significant effects on phenylephrine- and ANG II-induced vasoconstriction. However, VIP on sterically stabilized liposomes (SSL), a formulation where VIP assumes a predominantly α-helix conformation, significantly attenuates this response. Maximal effect is observed within 30 min and is no longer seen after 60 min. Empty SSL are inactive. Indomethacin has no significant effects on responses induced by VIP on SSL. The vasodilators ACh, nitroglycerin, calcium ionophore A-23187, 8-bromo-cAMP, and isoproterenol have no significant effects on phenylephrine- and ANG II-induced vasoconstriction. Collectively, these data suggest that vasoconstriction modulates VIP release in the in situ hamster cheek pouch and that α-helix VIP opposes α-adrenergic- and ANG II-induced vasoconstriction in this organ in a reversible, prostaglandin-, NO-, cGMP-, and cAMP-independent fashion.
Eating induced by perifornical cAMP is behaviorally selective and involves protein kinase activity
Authors: Gillard Elizabeth R. , Khan Arshad M. , Mouradi Bara , Nalamwar Omkar , Stanley B. Glenn
Published: December 2017

It has previously been shown that agents that increase endogenous cAMP elicit robust eating when injected into the perifornical hypothalamus (PFH) but not when injected into surrounding brain sites, suggesting that PFH cAMP may play a role in eating control. We report here that bilateral microinjection of the adenylyl cyclase activator 7-deacetyl-7- O-( N-methylpiperazino)-γ-butyryl-forskolin dihydrochloride (MPB forskolin; 300 nmol/0.3 μl) into the PFH is sufficient to elicit intense eating (up to 15.7 ± 2.3 g in 2 h) in satiated rats, without concomitant effects on other behaviors, including gnawing and drinking. In contrast, the inactive analog 1,9-dideoxyforskolin is ineffective, suggesting that the effects of MPB forskolin are behaviorally selective and pharmacologically specific. We also show that injection of the protein kinase A inhibitor H-89 (100 nmol) into the PFH reduced MPB forskolin-induced eating by up to 50%. Collectively, these results suggest that increased cAMP production in a single brain area may be sufficient to selectively generate a patterned, goal-oriented behavior by activating cAMP-dependent protein kinase.
Endothelin-1 increases the neuronal activity and augments the responses to glutamate in the NTS
Authors: Shihara Miwako , Hirooka Yoshitaka , Hori Nobuaki , Matsuo Isamu , Tagawa Tatsuya , Suzuki Satoshi , Akaike Norio , Takeshita Akira
Published: December 2017

The aims of this study were to determine 1) whether endothelin (ET)-1 affects the neuronal activity of the NTS neurons, 2) whether specific ET receptor antagonists affect the neuronal activity of the NTS neurons, and 3) whether ET-1 or ET receptor antagonists modulate the responses of the nucleus of the solitary tract (NTS) neurons to l-glutamate (Glu). The single-unit discharge was extracellularly recorded with a fine electrode from medulla brain slice preparations of rats. ET-1 and Glu were iontophoretically applied to the recorded neuron. Both ET-1 and Glu increased the neuronal activity. The ETAreceptor antagonist BQ-123 attenuated the basal neuronal activity. ET-1 augmented the magnitude of the increases in the neuronal activity evoked by Glu, and these responses were antagonized by BQ-123. These studies suggest the following conclusions: 1) ET-1 increases the neuronal activity of the NTS neurons via ETAreceptors, 2) endogenous ET plays a controlling role of the neuronal activity of NTS neurons, and 3) ET-1 augments the responses evoked by Glu, believed to be the neurotransmitter from the solitary tract, via ETAreceptors. These results suggest that ET-1 facilitates synaptic transmission in the NTS.
Decompression sickness risk in rats by microbial removal of dissolved gas
Authors: Kayar Susan R. , Miller Terry L. , Wolin Meyer J. , Aukhert Eugenia O. , Axley Milton J. , Kiesow Lutz A.
Published: December 2017

We present a method for reducing the risk of decompression sickness (DCS) in rats exposed to high pressures of H2. Suspensions of the human colonic microbe Methanobrevibacter smithii were introduced via a colonic cannula into the large intestines of the rats. While the rats breathed H2in a hyperbaric chamber, the microbe metabolized some of the H2diffusing into the intestine, converting H2and CO2to methane and water. Rate of release of methane from the rats, which was monitored by gas chromatography, varied with chamber H2pressure. This rate was higher during decompression than during compression, suggesting that during decompression the microbe was metabolizing H2stored in the rats’ tissues. Rats treated with M. smithii had a 25% (5 of 20) incidence of DCS, which was significantly lower ( P < 0.01) than the 56% (28 of 50) incidence of untreated controls, brought on by a standardized compression and decompression sequence. Thus using a microbe in the intestine to remove an estimated 5% of the body burden of H2reduced DCS risk by more than one-half. This method of biochemical decompression may potentially facilitate human diving.
Endogenous prostanoids modulate the ACTH and AVP responses to hypotension in late-gestation fetal sheep
Authors: Tong Haiyan , Lakhdir Farahaba , Wood Charles E.
Published: December 2017

We have previously reported that prostaglandin E2 and thromboxane A2 stimulate endocrine and cardiovascular responses similar to the responses to arterial hypotension. The present experiments were designed to test the hypothesis that prostanoids are involved in the generation of responses to hypotension induced by vena cava occlusion. Fetal sheep were either intact or subjected to a prior carotid sinus denervation and bilateral vagosympathetic nerve section. Indomethacin or vehicle was injected intravenously 90 min before the start of arterial hypotension. In intact fetuses treated with phosphate buffer, ACTH increased significantly from 83 ± 39 to 3,611 ± 774 pg/ml, arginine vasopressin (AVP) increased from 3.9 ± 0.5 to 1,079 ± 549 pg/ml, and cortisol increased from 4.7 ± 0.8 to 9.5 ± 1.7 ng/ml. Indomethacin treatment significantly reduced the magnitudes of the hormonal responses. Baroreceptor and chemoreceptor denervation attenuated the ACTH and AVP responses, but these responses were not further inhibited by indomethacin. We conclude that endogenous prostanoids partially mediate the reflex hormonal and hemodynamic responses to arterial hypotension in late-gestation fetal sheep.
Role of hypothalamic interleukin-1β in fever induced by cecal ligation and puncture in rats
Authors: Gourine Alexander V. , Rudolph Karin , Tesfaigzi Johannes , Kluger Matthew J.
Published: December 2017

Bacterial endotoxin induces fever by causing the release of interleukin (IL)-1β into the circulation or the brain. IL-1β is believed to mediate fever via triggering the production and/or release of IL-6 in the hypothalamus. The present study examined whether IL-1β and IL-6 in the hypothalamus of the rat are also involved in fever during bacterial sepsis caused by cecal ligation and puncture (CLP). CLP induces fever for 2 days. Polyclonal rabbit antibody against rat IL-1β (anti-IL-1β, 2 μg/μl) or control rabbit IgG (2 μg/μl) was unilaterally microinjected into the hypothalamus of rats immediately after or 24 h after CLP or sham-CLP surgery. Anti-IL-1β injected 24 h after CLP (when fever was already present) or sham-CLP surgery did not affect fever. Microinjection of anti-IL-1β into the hypothalamus immediately after surgery caused a significant decrease in body temperature during the night after CLP surgery and a 48% reduction of fever on the following day. Although blood plasma levels of IL-6 were significantly elevated 1.5, 6, 24, and 48 h after CLP surgery, there were no differences in IL-6 concentrations in the extracellular fluid of the anterior hypothalamus (collected by push-pull perfusion). These data suggest that fever due to bacterial sepsis is initiated by IL-1β within the hypothalamus, and this febrile response, unlike endotoxin-induced fever, is not accompanied by elevation in the hypothalamic concentration of IL-6.
Role of 17β-estradiol in the modulation of baroreflex sensitivity in male rats
Authors: Saleh Tarek M. , Connell Barry J.
Published: December 2017

Female mammals have an enhanced baroreflex sensitivity compared with their male counterparts, leading researchers to speculate that estrogen modulates autonomic tone. Therefore, this study tests the hypothesis that exogenous estrogen can enhance the baroreflex sensitivity of male rats. Male Sprague-Dawley rats anesthetized with thiobutabarbitol sodium (50 mg/kg) were instrumented to measure blood pressure and heart rate and for the intravenous injection of drugs. The baroreflex was tested using intravenous injections of phenylephrine (0.025, 0.05, and 0.1 mg/kg), and the cardiovascular responses were plotted to obtain a measure of the sensitivity of the cardiac baroreflex. Intravenous injection of estrogen produced dose-related increases in the baroreflex sensitivity due to an increase in the magnitude of the reflex bradycardia. In a separate group of animals, stimulation of the vagus nerve for 2 h resulted in a decrease in baroreflex sensitivity. This effect was blocked when estrogen (1 × 10−2mg/kg) was administered immediately before the end of stimulation. In conclusion, intravenous injection of estrogen in male rats significantly enhanced baroreflex sensitivity and blocked the attenuation in the baroreflex sensitivity observed after vagal stimulation.
IL-1β increases norepinephrine level in rat frontal cortex: involvement of prostanoids, NO, and glutamate
Authors: Kamikawa Hideki , Hori Tetsuro , Nakane Hideyuki , Aou Shuji , Tashiro Nobutada
Published: December 2017

The effects of local administration of interleukin-1β (IL-1β) were studied by using an intracerebral microdialysis technique in rats. A local injection of IL-1β (3 and 10 ng) induced an elevation of norepinephrine (NE) concentration in the medial prefrontal cortex (mPFC). IL-1-receptor antagonist (800 ng) completely blocked the IL-1β-induced NE increase. Diclofenac, a cyclooxygenase inhibitor (500 μM), and Nω-nitro-l-arginine, a nitric oxide (NO) synthase inhibitor (100 μM), applied through the dialysis probe, did not affect the initial rise in NE levels observed 20 min after injection of IL-1β but completely suppressed the late phase of IL-1β-induced NE increase at 40 min and thereafter. In contrast, local perfusion of 6-cyno-7-nitroquinoxaline-2,3-dione, a non- N-methyl-d-aspartic acid (NMDA) glutamate-receptor antagonist (50 μM), but notdl-2-amino-5-phosphonovaleric acid, an NMDA-receptor antagonist (100 μM), blocked both phases of IL-1β-induced NE increase. Furthermore, a microinjection of IL-1β elevated the extracellular concentration of glutamate in the mPFC. These findings suggest that the IL-1β-induced rise in NE levels in the mPFC is caused by activation of the glutamatergic system and the glutamate-induced increases in prostanoids and NO.
Circadian rhythms of lipoprotein lipase and hepatic lipase activities in intermediate metabolism of adult rat
Authors: Benavides Alex , Siches Mariona , Llobera Miquel
Published: December 2017

Although intermediate metabolism is known to follow circadian rhythms, little information is available on the variations in lipoprotein lipase (LPL) and hepatic lipase (HL) activities during the 24-h period, and there is also a lack of adequate statistical analysis. Here, adult male rats were fed ad libitum and kept at 21°C under 12:12-h light-dark cycles. They were killed in batches every 3 h over a 24-h period. Lipase activities were determined in plasma and fresh homogenates of epididymal white adipose tissue (EWAT), interscapular brown adipose tissue (IBAT), heart, skeletal muscle, and liver. Plasma insulin, corticosterone, glucose, triacylglycerol (TAG), cholesterol, glycerol, β-hydroxybutyrate, and liver and muscle glycogen were determined. Cosinor analysis was used to evaluate the presence (significance of fit of cosine curve to data and variance explained by rhythm) and characteristics of possible circadian rhythms [acrophase (φ), mesor, and amplitude]. Statistically significant circadian rhythms were detected for 1) all metabolites studied, except TAG, cholesterol, and liver HL activity; 2) LPL and HL activity in plasma (both φ in light phase); and 3) LPL activity in all tissues studied (φ: heart in light phase; skeletal muscle, IBAT, and EWAT in dark phase). Liver also showed a circadian rhythm of LPL activity, with φ near that in plasma. These findings demonstrate for the first time that, in physiological conditions, LPL activities in plasma and various tissues, including liver, and HL activity in plasma follow circadian rhythms. Their metabolic significance is discussed.
Effect of heating on the hemodynamic responses to vasoactive agents
Authors: Massett Michael P. , Lewis Stephen J. , Kregel Kevin C.
Published: December 2017

During hyperthermia, vasoconstrictor tone in the viscera is lost despite high levels of sympathetic neural outflow and plasma catecholamines, suggesting that vascular responsiveness to adrenergic receptor stimulation is reduced. The purpose of this study was to determine whether adrenoceptor-mediated control of vascular resistance is altered at high body core temperatures. The hemodynamic responses to adrenoceptor agonists were examined in chloralose-anesthetized rats heated to colonic temperatures (Tco) of 37, 39, and 41.5°C. Elevating Tcoto 39°C did not alter the hemodynamic responses to any of these agents. Further heating to 41.5°C markedly attenuated the hemodynamic responses to α- and β-adrenoceptor agonists. Similarly, the regional and systemic hemodynamic responses to ANG II and endothelin were also reduced at 41.5°C. In contrast, the hemodynamic responses to endothelium-dependent and -independent vasodilator agents were unchanged or slightly reduced at 41.5°C. The blunted hemodynamic responses observed at 41.5°C indicate that vascular reactivity to vasoconstrictor agents is reduced with hyperthermia and suggest that this nonspecific change in vascular responsiveness may contribute the circulatory collapse associated with high body temperatures.
Thermal acclimation of phase behavior in plasma membrane lipids of rainbow trout hepatocytes
Authors: Hazel Jeffrey R. , McKinley Susan J. , Gerrits Martin F.
Published: December 2017

The fluorescent probes laurdan (6-dodecanoyl-2-dimethylaminonapthalene) and N-[7-nitrobenz-2-oxa-1,3-diazol-4-yl] dipalmitoyl-l-α-phosphatidylethanolamine (NBD-PE) in addition to Fourier transform infrared spectroscopy (FTIR) were employed to measure the phase behavior and physical properties of hepatocyte plasma membranes isolated from the livers of thermally acclimated (5 and 20°C) rainbow trout ( Oncorhynchus mykiss). The primary objective was to determine the extent to which the phase behavior of membrane lipids is conserved at different growth temperatures. Arrhenius plots of laurdan-generalized polarization revealed a single discontinuity believed to reflect either the onset of the gel-fluid phase transition or the formation of gel phase microdomains, and this discontinuity occurred at significantly higher temperatures in membranes of 20°C (13.2 ± 0.7°C)- than 5°C (7.2 ± 0.1°C)-acclimated trout. Similarly, acclimation from 5 to 20°C increased both the onset temperature (from 2.0 ± 0.3 to 7.2 ± 0.6°C) and the thermal range (from 10.9 ± 0.5 to 16.0 ± 1.0) of the gel-fluid transition as assessed by FTIR. The gel-fluid transition midpoint (approximately −2°C) and completion temperatures (−9°C) were unchanged by thermal acclimation. The anisotropy of NBD-PE fluorescence displayed a distinct minimum in membranes of both warm- and cold-acclimated trout (reflecting alterations in lipid packing that in pure lipid membranes ultimately lead to the formation of nonlamellar phases) in the range of 56–58°C; only membranes of 5°C-acclimated trout displayed an additional minimum at significantly lower temperatures (24.5 ± 1.7°C). Collectively, these data suggest that the regulation of both the temperature at which gel phase lipids begin to form in response to cooling as well as the propensity of membrane lipids to form nonlamellar phases at higher temperatures may be key features of membrane organization subject to adaptive regulation.
Influence of acclimation temperature on mitochondrial DNA, RNA, and enzymes in skeletal muscle
Authors: Battersby Brendan James , Moyes Christopher D.
Published: December 2017

Skeletal muscle fibers typically undergo modifications in their mitochondrial content, concomitant with alterations in oxidative metabolism that occur during the development of muscle fiber and in response to physiological stimuli. We examined how cold acclimation affects the mitochondrial properties of two fish skeletal muscle fiber types and how the regulators of mitochondrial content differed between tissues. After 2 mo of acclimation to either 4 or 18°C, mitochondrial enzyme activities in both red and white muscle were higher in cold-acclimated fish. No significant differences were detected between acclimation temperatures in the abundance of steady-state mitochondrial mRNA (cytochrome- c oxidase 1, subunit 6 of F0F1-ATPase), rRNA (16S), or DNA copy number. Steady-state mRNA for nuclear-encoded respiratory (adenine nucleotide translocase 1) and glycolytic genes showed high interindividual variability, particularly in the cold-acclimated fish. Although mitochondrial enzymes were 10-fold different between the two muscle types, mitochondrial DNA copy number differed only 4-fold. The relative abundance of mitochondrial mRNA and nuclear mRNA in red and white muscle reflected the differences in copy number of their respective genes. These data suggest that the response to physiological stimuli and determination of tissue-specific mitochondrial properties likely result from the regulation of nuclear-encoded genes.
Leptin causes body weight loss in the absence of in vivo activities typical of cytokines of the IL-6 family
Authors: Agnello Davide , Meazza Cristina , Rowan Christopher G. , Villa Pia , Ghezzi Pietro , Senaldi Giorgio
Published: December 2017

To investigate if leptin shares in vivo activities with interleukin (IL)-6 family cytokines, it was tested in normal mice for the ability, after a single injection, to induce the acute-phase protein serum amyloid A, to potentiate the induction by IL-1 of serum corticosterone and IL-6, and to inhibit the induction by lipopolysaccharide of serum tumor necrosis factor and, after seven daily injections, to cause body weight loss and to change peripheral blood cell counts. At a 0.5 mg/kg dose, leptin caused body weight loss but did not show any of the other activities above. At a dose of 5 mg/kg, which also caused body weight loss, leptin potentiated the induction by IL-1 of serum corticosterone and IL-6 but did not show any other activity. In addition to causing body weight loss, leptin shows only some of the in vivo activities typical of IL-6 family cytokines and only if used at a dose that exceeds the one sufficient to affect body weight. In vivo, leptin seems to chiefly control body weight and not inflammatory or hematopoietic processes.
Febrile nonresponsiveness of vagotomized animals: is it due to endotoxin translocation from the gut and tolerance?
Authors: Romanovsky Andrej A.
Published: December 2017

The following is the abstract of the article discussed in the subsequent letter:

Scammell, Thomas E., John D. Griffin, Joel K. Elmquist, and Clifford B. Saper. Microinjection of a cyclooxygenase inhibitor into the anteroventral preoptic region attenuates LPS fever. Am. J. Physiol.274 ( Regulatory Integrative Comp. Physiol. 43): R933–R935, 1998.—Considerable evidence supports the role of prostaglandins in fever production, but the neuroanatomic sites of prostaglandin synthesis that produce fever remain unknown. With the use of a novel microinjection technique, we injected the cyclooxygenase inhibitor ketorolac into the preoptic area (POA) to determine which preoptic regions produce the prostaglandins required for fever. Initial experiments demonstrated that intravenous ketorolac blocked the fever normally produced by lipopolysaccharide (LPS) 5 μg/kg iv. Microinjection of ketorolac into the POA had no effect on body temperature, and injection of artificial cerebrospinal fluid into the POA did not alter LPS fever. Injection of ketorolac into the anteroventral POA markedly decreased the fever produced by LPS, compared with injections into more rostral, caudal, or dorsal locations. These observations indicate that prostaglandin synthesis in the anteroventral preoptic region is necessary for the production of fever.
Differential suppression of upper airway motor activity during carbachol-induced, REM sleep-like atonia
Authors: Fenik Victor , Davies Richard O. , Pack Allan I. , Kubin Leszek
Published: December 2017

Microinjections of carbachol into the pontine tegmentum of decerebrate cats have been used to study the mechanisms underlying the suppression of postural and respiratory motoneuronal activity during the resulting rapid eye movement (REM) sleep-like atonia. During REM sleep, distinct respiratory muscles are differentially affected; e.g., the activity of the diaphragm shows little suppression, whereas the activity of some upper airway muscles is quite strong. To determine the pattern of the carbachol-induced changes in the activity of different groups of upper airway motoneurons, we simultaneously recorded the efferent activity of the recurrent laryngeal nerve (RL), pharyngeal branch of the vagus nerve (Phar), and genioglossal branch of the hypoglossal (XII) and phrenic (Phr) nerves in 12 decerebrate, paralyzed, vagotomized, and artificially ventilated cats. Pontine carbachol caused a stereotyped suppression of the spontaneous activity that was significantly larger in Phar expiratory (to 8.3% of control) and XII inspiratory motoneurons (to 15%) than in Phr inspiratory (to 87%), RL inspiratory (to 79%), or RL expiratory motoneurons (to 72%). The suppression in upper airway motor output was significantly greater than the depression caused by a level of hypocapnia that reduced Phr activity as much as carbachol. We conclude that pontine carbachol evokes a stereotyped pattern of suppression of upper airway motor activity. Because carbachol evokes a state having many neurophysiological characteristics similar to those of REM sleep, it is likely that pontine cholinoceptive neurons have similar effects on the activity of upper airway motoneurons during both states.
Inhibitors of alternative pathways of arachidonate metabolism differentially affect fever in mice
Authors: Kozak Wieslaw , Archuleta Inez , Mayfield Kimberly P. , Kozak Anna , Rudolph Karin , Kluger Matthew J.
Published: December 2017

Inhibitors of cyclooxygenases prevent fever. The purpose of this study was to test the hypothesis that selective and dual inhibitors of the other enzyme systems of arachidonic acid oxygenation (i.e., lipoxygenase and epoxygenase) affect the time course or magnitude of fever in mice. Swiss Webster mice kept at 30°C ambient temperature were implanted with biotelemeters to monitor body temperature. Fever was induced by intraperitoneal injection of lipopolysaccharide at doses from 10 μg/kg to 2.5 mg/kg. Phenidone (20–30 mg/kg ip), a dual lipoxygenase and cyclooxygenase inhibitor, prevented fever in these mice, but esculetin (1–10 mg/kg ip), a selective inhibitor of lipoxygenases, did not affect fever. Intramuscular injection of nordihydroguaiaretic acid (10–20 mg/kg), a dual lipoxygenase and epoxygenase inhibitor, as well as SKF-525A (5 mg/kg ip) and clotrimazole (20 mg/kg im), inhibitors of the cytochrome P-450/epoxygenase pathway, augmented fever in mice. Indomethacin (5 mg/kg ip), an inhibitor of cyclooxygenase, suppressed the exacerbation of fever due to clotrimazole, suggesting that the epoxygenase inhibitor-induced potentiation of fever in mice is a prostaglandin-mediated effect. From this study, we hypothesize that the cytochrome P-450/epoxygenase branch of the arachidonate cascade is involved in antipyresis and in controlling the upper limit of fever.
Continuity between wound macrophage and fibroblast phenotype: analysis of wound fibroblast phagocytosis
Authors: Arlein Wes J. , Shearer Jeffry D. , Caldwell Michael D.
Published: December 2017

Analysis of phagocytic activity in wound fibroblasts was chosen as a means to assess the possible continuity between macrophage and fibroblast phenotypes. Fibroblast phagocytosis of uncoated, IgG-coated, or collagen-coated fluorescent beads was analyzed by flow cytometry in vivo and in vitro. Phagocytosis of fluorescent beads by procollagen I-positive cells (fibroblasts) was evaluated in vivo by injecting beads into subcutaneously implanted sponge wounds in anesthetized Fisher rats. Phagocytic activity of a purified population of wound fibroblasts was measured in vitro and correlated with oxidation state using hydroethidium. In the wound environment, 50–60% of the cells that engulfed uncoated, IgG-coated, or collagen-coated beads were procollagen I-positive cells (i.e., fibroblasts). Procollagen I-positive cells engulfed uncoated and IgG-coated beads in preference to collagen-coated beads in vivo. Cultured wound fibroblasts engulfed uncoated, IgG-coated, and collagen-coated particles. The majority of fibroblasts that engulfed beads were in an elevated oxidation state. We conclude that substantial fibroblast phagocytosis occurs in the wound, but scavenger receptor-mediated fibroblast phagocytosis is different from that of macrophages. Additional markers will be helpful in defining the macrophage fibroblast continuum.
Altered expression of type 2 CRH receptor mRNA in the VMH by glucocorticoids and starvation
Authors: Makino Shinya , Nishiyama Mitsuru , Asaba Koichi , Gold Philip W. , Hashimoto Kozo
Published: December 2017

In the rat, high-dose corticosterone (Cort) administration, the hypercortisolism of starvation, and adrenalectomy are all associated with decreased food intake and weight loss. We report here a study of the effects of high-dose Cort administration, starvation, and adrenalectomy on two peripheral hormones known to influence food intake and energy use, insulin and leptin. We also studied the impact of these interventions on the levels of type 2 corticotropin-releasing hormone receptor (CRHR-2) mRNA in the hypothalamic paraventricular nucleus (PVN) and ventromedial hypothalamus (VMH). The VMH is classically referred to as the satiety center because electrical stimulation of the VMH leads to inhibition of food intake, whereas CRHR-2 are thought to transduce the profound anorexogenic effects of CRH or its related peptide urocortin. Starvation and adrenalectomy each lowered plasma insulin and leptin levels and were associated with decrements in CRHR-2 mRNA levels in the VMH. Cort administration increased plasma leptin levels profoundly, as well as plasma insulin levels and the levels of VMH CRHR-2 mRNA. Under all experimental conditions, a positive correlation was seen between plasma leptin levels and VMH CRHR-2 mRNA. These data suggest that decreased food intake and weight loss after high-dose Cort administration at least partially depend on the profound impact of Cort on plasma leptin secretion in the rat; they suggest, moreover, an additional mechanism for the satiety-inducing effects of leptin, namely increasing CRHR-2 in the VMH. The concordance of a fall in plasma insulin and leptin levels with the fall in VMH CRHR-2 mRNA levels further supports the idea that compensatory responses during starvation and adrenalectomy include not only the disinhibiting effects of reduced insulin and leptin levels on appetite through already-described mechanisms but also via an effect of leptin on VMH CRHR-2. Neither Cort administration, starvation, nor adrenalectomy influenced the levels of CRHR-2 mRNA in the PVN, suggesting that these receptors are differentially regulated in different hypothalamic regions.
Cytokines mediate protective stimulation of glucocorticoid output during autoimmunity: involvement of IL-1
Authors: Del Rey Adriana , Klusman Isabel , Besedovsky Hugo O.
Published: December 2017

Endogenous glucocorticoid levels are increased during experimental autoimmune encephalomyelitis (EAE) in Lewis rats. Although this endocrine response is essential for survival, the mechanism that triggers the stimulation of glucocorticoid output during the disease remains unknown. We report here that 1) after immunization with the encephalitogenic antigen myelin basic protein (MBP), increased blood glucocorticoid levels are not only observed in Lewis rats, but also in PVG rats, which do not develop EAE; 2) immune cells obtained from animals with EAE and stimulated in vitro with MBP produced mediators that increased glucocorticoid levels when administered to naive recipients; and 3) acute in vivo blockade of interleukin-1 (IL-1) receptors inhibited, to a large extent, the increase in corticosterone levels during EAE. These results show that the increase in corticosterone levels after immunization with MBP can be dissociated from the stress of the paralytic attack that characterizes EAE. Furthermore, they indicate that an endocrine response, which is decisive for the prevention or moderation of EAE, is mainly the result of the stimulation of the hypothalamic-pituitary-adrenal axis by cytokines produced during the immune response that induces the autoimmune disease.
Role of central catecholaminergic pathways in the actions of endogenous ANG II on sympathetic reflexes
Authors: Gaudet Elisabeth A. , Godwin Shirley J. , Head Geoffrey A.
Published: December 2017

In the present study, we examined the effect of blockade of the brain stem renin-angiotensin system on renal sympathetic baroreflexes and chemoreflexes in conscious rabbits and examined the role of central catecholaminergic pathways in these responses. Eleven rabbits underwent preliminary surgical instrumentation and pretreatment with central 6-hydroxydopamine (6-OHDA, 500 μg/kg) or ascorbic acid 6 wk before the commencement of the experiments. Baroreflex curves were determined under conditions of normoxia and hypoxia (10% O2+ 3% CO2) before and after central administration of either Ringer solution, the ANG II receptor antagonist losartan (10 μg), or the angiotensin-converting enzyme inhibitor enalaprilat (500 ng) on separate days. Losartan increased the upper plateau and the range of the mean arterial pressure (MAP)-renal sympathetic nerve activity (RSNA) curve (79 and 78%, respectively) in intact rabbits, whereas this effect was not observed in 6-OHDA-pretreated rabbits. Hypoxia elicited an increase in resting RSNA (111% in intact rabbits and 74% in 6-OHDA-injected rabbits) and elevated the upper plateau of the RSNA-MAP curve in both groups (89% in intact rabbits and 114% in 6-OHDA-injected rabbits). During hypoxia, losartan and enalaprilat increased the RSNA upper plateau in intact rabbits but had no effect in 6-OHDA-pretreated rabbits. No effects on the MAP-heart rate baroreflex curves were observed. Thus the effect of losartan to increase RSNA, particularly during hypoxia and baroreceptor unloading, being abolished by central noradrenergic depletion suggests that the endogenous ANG II which normally causes an inhibition of renal sympathetic motoneurons is dependent on the integrity of central catecholaminergic pathways.