Abstract P389: Post-traumatic Stress-induced Sensitization of Angiotensin II Hypertension is Reversed by Blockade of Angiotensin-converting Enzyme or Tumor Necrosis Factor-alpha

Using an Induction-Delay-Expression experimental paradigm, our previous studies demonstrated that post-traumatic stress disorder (PTSD) sensitizes angiotensin (ANG) II-elicited hypertension, which was associated with upregulation of central renin-angiotensin system (RAS) components and proinflammatory cytokines (PICs). The present study investigated whether inhibition of angiotensin-converting enzyme (ACE) or tumor necrosis factor-α (TNF-α) prior to PTSD blocks sensitization of ANG II-elicited hypertensive response. The resident-intruder paradigm was used to model PTSD. Each intruder rat (male Sprague-Dawley) was pretreated with ACE inhibitor (captopril, 0.5 mg/Ml) or with TNF-α inhibitor (pentoxifylline, PTX, 100 mg/kg/day) in the drinking water for two weeks and then exposed to a different resident (male Long-Evans) for 2 hours on three days with each session separated by 1 day. Beginning 3 days after the last exposure, the intruder (PTSD) rats and unstressed control rats received a subcutaneous infusion of ANG II (120 ng/kg/min) for 2 weeks. The PTSD rats had a significantly enhanced hypertensive response to the ANG II infusion and an upregulation of mRNA expression of RAS and PIC components and of a microglial marker in the lamina terminalis (LT) when compared to control rats. Both the sensitized hypertensive response and enhanced gene expression were blocked by pre-treatment with either ACE inhibitor or TNF-α antagonist. These results suggest

that upregulation of the brain RAS and PICs produced by a severe stress contribute to PTSD-induced sensitization of the hypertensive response to ANG II.

Abstract P306: Maternal High Fat Diet Acts on the Brain to Induce Baroreflex Dysfunction and Sensitization of Angiotensin II-induced Hypertension in Adult Offspring

Accumulating evidence indicates that maternal high fat diet (HFD) is associated with metabolic syndrome and cardiovascular disease in adult offspring. The present study tested the hypothesis that maternal HFD modulates the brain renin-angiotensin system (RAS), oxidative stress and proinflammatory cytokines that alters angiotensin II and tumor necrosis factor-α (TNF-α) actions to sensitize the angiotensin II-elicited hypertensive response in adult offspring. All offspring were cross-fostered by dams on the same or opposite diet to yield 4 groups: offspring from normal fat control diet (CD)-fed dams suckled by CD-fed dams (OCC) or by HFD-fed dams (OCH) and offspring from HFD-fed dams fed HFD suckled by CD-fed dams (OHC) or by HFD-fed dams (OHH). RT-PCR analyses of the lamina terminalis (LT) and paraventricular nucleus (PVN) indicated upregulation of mRNA expression of several RAS components, NADPH oxidase and proinflammatory cytokines in 10-week old male offspring of dams fed HFD during either pregnancy, lactation or both (OHC, OCH and OHH). These offspring also showed decreased baroreflex sensitivity and increased pressor responses to intracerebroventricular microinjection of either angiotensin II or TNF-α. Furthermore, chronic systemic infusion of angiotensin II resulted in enhanced upregulation of mRNA expression of RAS components, NADPH oxidase and proinflammatory cytokines in the LT and PVN and an augmented hypertensive response in the OHC, OCH and OHH groups when compared to the OCC. The results suggest that maternal HFD blunts baroreflex function and enhances pressor responses to angiotensin II or proinflammaroty cytokines through upregulation of the brain RAS, oxidative stress and inflammation.

Brain Transforming Growth Factor-β Resists Hypertension Via Regulating Microglial Activation

BACKGROUND AND PURPOSE

Hypertension is the major risk factor for stroke. Recent work unveiled that hypertension is associated with chronic neuroinflammation; microglia are the major players in neuroinflammation, and the activated microglia elevate sympathetic nerve activity and blood pressure. This study is to understand how brain homeostasis is kept from hypertensive disturbance and microglial activation at the onset of hypertension.

METHODS

Hypertension was induced by subcutaneous delivery of angiotensin II, and blood pressure was monitored in conscious animals. Microglial activity was analyzed by flow cytometry and immunohistochemistry. Antibody, pharmacological chemical, and recombinant cytokine were administered to the brain through intracerebroventricular infusion. Microglial depletion was performed by intracerebroventricular delivering diphtheria toxin to CD11b-diphtheria toxin receptor mice. Gene expression profile in sympathetic controlling nucleus was analyzed by customized qRT-PCR array.

RESULTS

Transforming growth factor-β (TGF-β) is constitutively expressed in the brains of normotensive mice. Removal of TGF-β or blocking its signaling before hypertension induction accelerated hypertension progression, whereas supplementation of TGF-β1 substantially suppressed neuroinflammation, kidney norepinephrine level, and blood pressure. By means of microglial depletion and adoptive transfer, we showed that the effects of TGF-β on hypertension are mediated through microglia. In contrast to the activated microglia in established hypertension, the resting microglia are immunosuppressive and important in maintaining neural homeostasis at the onset of hypertension. Further, we profiled the signature molecules of neuroinflammation and neuroplasticity associated with hypertension and TGF-β by qRT-PCR array.

CONCLUSIONS

Our results identify that TGF-β-modulated microglia are critical to keeping brain homeostasis responding to hypertensive disturbance.

Goosefish Lophius americanus fecundity and spawning frequency, with implications for population reproductive potential

To improve knowledge of goosefish Lophius americanus' reproductive biology, females were collected during 2009-2012 from the Mid-Atlantic Bight shelf region of the U.S. east coast. Batch fecundity increased with total length (L_T ), from 229 100 to 2 243 300 mature oocytes per female (L_T range: 55·5-112 cm; n = 54). This estimate of fecundity at L_T is lower than one derived from a sample collected during 1982-1985. Examination of whole oocyte diameters in different months indicated that L. americanus is a serial spawner, releasing more than one egg veil per spawning season, as suspected or observed for other Lophius species. Seasonality of spawning was evident from whole oocytes and gonad histology, and from larval fish surveys spanning the U.S. north-east shelf, and confirmed a protracted (c. 6 months) spawning period. Peak spawning activity progressed northward from spring to autumn. The population-level implications of these results were explored by estimating population reproductive potential (P_RP ), which considered the value of both current and future per capita reproduction using decade-specific age structure and fecundity at length. P_RP is now more than 50% lower compared with the historical period (1982-1985), a result of the lower proportions of large females and reduced fecundity across all sizes. Mechanisms that could explain this loss of stock productivity are fishing-induced size-age truncation or regime shifts in egg production caused by changes in energy density of common forage species.

Measuring the efficacy of flunixin meglumine and meloxicam for lame sows using a GAITFour pressure mat and an embedded microcomputer-based force plate system

Pain associated with lameness on farm is a negative affective state and has a detrimental impact on individual farm animal welfare. Animal pain can be managed utilizing husbandry tools and through pharmacological approaches. Nonsteroidal anti-inflammatory drugs including meloxicam and flunixin meglumine are compounds used in many species for pain management because they are easy to administer, long lasting, and cost-effective. Assessing an animal's biomechanical parameters using such tools as the embedded microcomputer-based force plate system and GAITFour pressure mat gait analysis walkway system provides an objective, sensitive, and precise means to detect animals in lame states. The objectives of this study were to determine the efficacy of meloxicam and flunixin meglumine for pain mitigation in lame sows using the embedded microcomputer-based force plate system and GAITFour pressure mat gait analysis walkway system. Lameness was induced in 24 mature mixed-parity sows using a chemical synovitis model and compared 3 treatments: meloxicam (1.0 mg/kg per os), flunixin meglumine (2.2 mg/kg intramuscular) and sterile saline (intramuscular). Weight distribution (kg) for each foot was collected twice per second for a total of 5 min for each time point using the embedded microcomputer-based force plate system. Stride time, stride length, maximum pressure, activated sensors, and stance time were collected using 3 quality walks (readings) for each time point using the GAITFour pressure mat gait analysis walkway system. Sows administered flunixin meglumine or meloxicam tolerated more weight on their lame leg compared with saline sows (P < 0.005). Sows administered flunixin meglumine or meloxicam had smaller differences in stance time, maximum pressure, and activated sensors between the sound and lame legs compared with saline-treated sows between 37 and 60 h after lameness induction (P < 0.03). In conclusion, flunixin meglumine and meloxicam administration mitigated pain sensitivity in sows after lameness induction when pain sensitivity was evaluated with the embedded microcomputer-based force plate system and GAITFour pressure mat gait analysis walkway system. Analgesic drugs may be a key tool to manage negative pain affective states associated with lameness.

Abstract P193: Upregulation of Brain Renin-angiotensin System and Inflammation Mediates Leptin Sensitization of Angiotensin Ii-induced Hypertension

Leptin, an adipocyte-derived hormone, contributes to the increase in blood pressure (BP) associated with obesity. Obesity has also been shown to promote the renin-angiotensin system (RAS) activity and inflammation in the hypothalamus that increase BP and sympathetic activity. Our previous studies using an Induction-Delay-Expression experimental design demonstrated that a central leptin pretreatment resulted in an enhanced hypertensive response to subsequent treatment with angiotensin (ANG) II. The present study tested whether this central leptin sensitization of ANG II-induced hypertension is mediated by an increase in RAS acitivity and inflammation in the brain. Male rats prepared for telemetry BP recording and were pretreated during Induction with central leptin (20 ng/kg/min, ICV) alone or with either ANG II type 1 receptor (AT1R) antagonist irbesartan (125 μg/d) or the TNF-α synthesis inhibitor pentoxifylline (10 μg/h) for one week. After one week Delay, rats were treated during Expression with subcutaneous ANG II (120 ng/kg/min) for 2 weeks. The animals pretreated with central leptin responded with enhanced hypertension to ANG II ([[Unable to Display Character: &#8710;]]39.3±3.8 mmHg vs. [[Unable to Display Character: &#8710;]]21.2±5.2 mmHg). Central infusion of pentoxifylline or irbesartan during Induction blocked the sensitization produced by central leptin. RT-PCR analysis of tissue from the lamina terminalis indicated that leptin up-regulated mRNA expression of several components of the RAS and proinflammatory cytokines including AT1R, angiotensin converting enzyme, TNF-α and interleukin 1β. The results indicate that leptin-induced sensitization of ANG II-elicited hypertension is mediated by upregulation of central RAS and proinflammatory cytokines.

Consumption of a high n-3 polyunsaturated fatty acid diet during gradual mild physiological stress in rats

n-3 Polyunsaturated fatty acids (n-3PUFAs) may be beneficial for anxiety and depression under stressful conditions. Studies however, typically utilise physical or sudden physiological stress, while gradual physiological stress is also relevant to human conditions. Using deoxycorticosterone acetate (DOCA) administration to induce gradual physiological stress, this study investigated the impact of n-3PUFAs under gradual physiological stress in rats. Animals (aged 2 months) (N=8-12/group) received daily injections of DOCA or vehicle and were concurrently fed a high n-3PUFA or control diet for eight weeks. Behavioural measures were taken throughout. Behavioural tests and physiological measures were conducted after six and eight weeks respectively. DOCA administration decreased plasma renin, plasma proteins and relative adrenal weight, and increased water intake, relative kidney weight, and anxiety in the open field. These findings demonstrate disruptions to the renin-angiotensin-aldosterone system, a result of mild physiological stress, that also impact on anxiety behaviours. No effects of n-3PUFAs were found.

Abstract 441: Sex Differences in Microglia Activation During Subpressor Dose of Angiotensin (Ang) II Sensitization of Subsequent Pressor Dose of Ang II

In previous studies using the Induction-Delay-Expression (I-D-E) experimental design we have shown that there are sex differences in the effects of one-week Ang II pre-treatment to sensitize the brain to produce an enhanced hypertensive response to subsequent Ang II. In other studies, we have shown that females are protected from hypertension and brain infiltration of T lymphocytes during Ang II infusion. The purpose of the present study was to test whether there is a sex difference in brain microglia activation on the sensitizing effects of Ang II. The present studies followed an I-D-E experimental design. Three male and three female Sprague-Dawley rats were assigned to each of the following experimental groups: 1) Control ( I saline + D) ; 2) I-Ang II+D ( I with subpressor dose of Ang II, 10 ng/kg/min); 3) I-saline+D+E-Ang II (I with saline plus E with a pressor dose of Ang II, 120 ng/kg/min); 4) I-Ang II+D+E-Ang II (I with subpressor dose of Ang II plus E with pressor dose of Ang II). At the end of the experiment, animals were anesthetized and perfused with formalin. Thirty-micron frozen slices of the area postrema (AP), nucleus tractus solitarius (NTS), and subfornical organ (SFO) were processed for IHC staining with IBa-1 microglia antibody (WAKO, 1:200). The number of IBa-1+ activated microglia (MG) in each region were counted in an approx 3 consecutive brain slices from 3 separate animals. The subpressor dose of Ang II resulted in a significant increase in NTS activated microglia in males (MG 19.2 vs. 5.1) but not in females (MG 1.5 vs 2.3) when compared to control. In females, the pressor dose of Ang II did not increase the activated microglia in the NTS. The numbers of activated microglia in the AP was similar in males and females in the I-Ang II+D+E-Ang II group, but in the I-Sal+D+E-Ang II, males had greater number of MG in the AP as compared to females (21.5 vs 11.8, P=0.05). The number of MG in the SFO were low across all groups compared to the number of MG in other regions examined (males I-Ang II+D+E-Ang II group averaged 3.9 MG vs females averaged 2.3 MG). These results suggest that sex differences observed in the brain sensitization to Ang II may involve differential induction of microglia activation in selective brain regions important for Ang II generation of hypertension.

Evaluation of mechanical and thermal nociception as objective tools to measure painful and nonpainful lameness phases in multiparous sows

The objective of this study was to quantify pain sensitivity differences using mechanical nociception threshold (MNT) and thermal nociception threshold (TNT) tests when sows were in painful and nonpainful transient lameness phases. A total of 24 mixed parity crossbred sows (220.15 ± 21.23 kg) were utilized for the MNT test, and a total of 12 sows (211.41 ± 20.21 kg) were utilized for the TNT test. On induction day (D0), all sows were anesthetized and injected with Amphotericin B (10mg/mL) in the distal interphalangeal joint space in both claws of one randomly selected hind limb to induce transient lameness. Three days were compared: (1) D-1 (sound phase, defined as 1 d before induction), (2) D+1 (most lame phase, defined as 1 d after induction), and (3) D+6 (resolution phase, defined as 6 d after induction). After completion of the first round, sows were given a 7-d rest period and then the procedures were repeated with lameness induced in the contralateral hind limb. During the MNT test, pressure was applied perpendicularly to 3 landmarks in a randomized sequence for each sow: 1) middle of cannon on the hind limb (cannon), 2) 1 cm above the coronary band on the medial hind claw (medial claw), and 3) 1 cm above the coronary band on the lateral hind claw (lateral claw). During the TNT test, a radiant heat stimulus was directed 1 cm above the coronary band. The data were analyzed using the MIXED procedure in SAS with sow as the experimental unit. Differences were analyzed between sound and lame limbs on each day. For the MNT test, pressure tolerated by the lame limb decreased for every landmark (P < 0.05) when comparing D-1 and D+1. The sound limb tolerated more pressure on D+1 and D+6 than on baseline D-1 (P < 0.05). Thermal stimulation tolerated by the sound limb did not change over the 3 d (P > 0.05). However, the sows tolerated less heat stimulation on their lame limb on D+1 compared to D-1 levels (P < 0.05). Both MNT and TNT tests indicated greater pain sensitivity thresholds when sows were acutely lame.

Determining the influence of dietary roughage concentration and source on ruminal parameters related to sulfur toxicity

Cattle feedlot diets often include ethanol coproducts that provide excess dietary sulfate, which is reduced to sulfide by ruminal bacteria and can be converted to hydrogen sulfide, which has been correlated to S toxicity. The objective of this study was to determine the impact of feeding varying concentrations of NDF from chopped cornstalks (CS) or chopped bromegrass hay (BH) on ruminal pH, ruminal H2S concentration, and DMI of steers fed a high-S finishing diet. Five ruminally fistulated steers (595 ± 87 kg BW) were used in a 6 × 6 Latin square with 14-d periods and fed diets containing 0.45% S from a mixture of dried distillers grains and condensed corn distillers solubles. The study was a 2 × 3 factorial arrangement of treatments with 2 roughage sources--CS or BH--and 3 concentrations of added roughage NDF (rNDF)--4, 7, or 10%. Steers had individual ad libitum access to feed and adapted to each diet for the first 7 d of each period. Effective NDF linearly increased (P < 0.01) as rNDF increased and did not differ between sources (P = 0.44). There was no effect of concentration or source of rNDF on DMI (P ≥ 0.69). Steer behavior was observed on d 13 of each period for 3 h postfeeding. Source of rNDF did not affect time at bunk, DMI during observation, or rate of DMI (P ≥ 0.42). Time at bunk linearly increased as rNDF increased (P = 0.01), while rate of DMI linearly decreased (P = 0.02). Area under the curve for ruminal pH of 5.4, 5.6, and 5.8, calculated using data from d 8 to 14 via an indwelling ruminal bolus, were linearly decreased (P ≤ 0.03) as rNDF increased. Manual ruminal pH taken 6 h postfeeding on d 14 of each period did not differ by source (P = 0.12) but linearly increased (P < 0.01) as rNDF increased. Ruminal H2S concentrations measured 6 h postfeeding on d 14 of each period did not differ by source (P = 0.47) but linearly decreased (P < 0.01) as rNDF increased (0.62, 0.35, 0.31 g/m(3) for 4, 7, and 10% rNDF, respectively). A segmented linear model was found to best fit the ruminal pH and H2S relationship data, suggesting that at or below a pH of 5.6 ± 0.08 with 95% confidence intervals of 5.4 and 5.8, pH is a strong predictor of H2S (P ≤ 0.05), while above this pH range H2S concentrations are not well correlated with ruminal pH (P > 0.50). In conclusion, adding at least 7% NDF from CS or BH to high-S feedlot cattle diets will increase ruminal pH and decrease H2S concentrations, thus decreasing potential for S toxicity.

Angiotensinergic and cholinergic receptors of the subfornical organ mediate sodium intake induced by GABAergic activation of the lateral parabrachial nucleus

Bilateral injections of the GABA(A) agonist muscimol into the lateral parabrachial nucleus (LPBN) induce 0.3 M NaCl and water intake in satiated and normovolemic rats, a response reduced by intracerebroventricular (icv) administration of losartan or atropine (angiotensinergic type 1 (AT₁) and cholinergic muscarinic receptor antagonists, respectively). In the present study, we investigated the effects of the injections of losartan or atropine into the subfornical organ (SFO) on 0.3M NaCl and water intake induced by injections of muscimol into the LPBN. In addition, using intracellular calcium measurement, we also tested the sensitivity of SFO-cultured cells to angiotensin II (ANG II) and carbachol (cholinergic agonist). In male Holtzman rats with cannulas implanted bilaterally into the LPBN and into the SFO, injections of losartan (1 μg/0.1 μl) or atropine (2 nmol/0.1 μl) into the SFO almost abolished 0.3M NaCl and water intake induced by muscimol (0.5 nmol/0.2 μl) injected into the LPBN. In about 30% of the cultured cells of the SFO, carbachol and ANG II increased intracellular calcium concentration ([Ca²⁺](i)). Three distinct cell populations were found in the SFO, i.e., cells activated by either ANG II (25%) or carbachol (2.6%) or by both stimuli (2.3%). The results suggest that the activation of angiotensinergic and cholinergic mechanisms in the SFO is important for NaCl and water intake induced by the deactivation of LPBN inhibitory mechanisms with muscimol injections. They also show that there are cells in the SFO activated by both angiotensinergic and cholinergic stimuli, perhaps those involved in the responses to muscimol into the LPBN.

Development and refinement of a technique for short-term intravascular auricular vein catheter placement in mature sows

Intravenous drug administration in adult swine is difficult to perform due to inaccessible superficial veins and thick subcutaneous fat layers. However, successful intravenous drug administration is critical for many biomedical applications including pharmacokinetic studies as extravascular drug administration can influence the drug’s absorption and elimination rate. The purpose of this study was to develop and refine an effective technique for indwelling auricular vein catheter placement in the conscious mature sow. We developed a protocol using a topical anesthetic cream and minimal physical restraint to place indwelling catheters in the auricular vein of six multiparous sows. This method was quick (3 min 20 s ± 8 s [mean ± SE per catheter]), effective (11/12 catheters successfully placed) and reliable, allowing a large drug volume (20–22 mL) to be administrated successfully during the trial without relying on prolonged restraint or general anesthesia of the sow.

Abstract 515: Central Angiotensin (ang) (1-7) Inhibits the Sensitizing Effects of a Low Dose Ang Ii in Hypertension Produced by a Subsequent Slow Pressor Dose of Ang Ii in Male and Female Rats

Previous studies using an Induction-Delay-Expression (I-D-E) experimental design demonstrated that pre-treatment with ANG II for 1 week produces a sensitized hypertensive response to subsequent ANG II administration in males but not in females. In this sensitization process, several brain renin-angiotensin-aldosterone system components including angiotensin converting enzyme 2 (ACE2) expressions were enhanced. It has been shown that ANG (1-7), formed from ANG II by ACE2, plays an anti-hypertensive role in the central nervous system. The present study tested whether central ANG (1-7) protects against the sensitizing effects of a low dose of ANG II.

Male and female rats were implanted for telemetered blood pressure (BP) recording. During I low doses of ANG II alone or with concurrent icv administration of ANG (1-7) or its antagonist A-779 were given for 1 week. After a 1 week rest ( D ), a slow pressor dose of ANG II was given for 2 weeks ( E ).

In males, the low dose of ANG II during I resulted in an enhanced pressor response to the subsequent slow pressor dose of ANG II given during E in comparison to those rats receiving vehicle during I (Δ42.8±7.2 vs Δ21.2±5.3 mmHg). Central administration of ANG (1-7) during I blocked the low dose ANG II-induced sensitization (Δ16.4±4.0 mmHg). In contrast, the low dose of ANG II did not sensitize the hypertensive response in females to the subsequent slow pressor dose of ANG II (Δ13.0±5.4 vs Δ9.9±3.4 mmHg). Central blockade of ANG (1-7) by icv infusion of A-779 during I resulted in sensitization by the low dose of ANG II (Δ26.7±2.0 mmHg) in females. The results indicate that ANG (1-7) plays a protective role during the sensitization process, especially in females, and its administration can attenuate the development of ANG II-induced hypertension in both male and female.

Validation of a lameness model in sows using physiological and mechanical measurements

The objective of this study was to develop a validated, transient, chemically induced lameness model in sows using subjective and objective lameness detection tools. Experiment 1 determined an effective joint injection technique based on volume and placement of dye using feet collected from 9 finisher pigs and 10 multiparity cull sow carcasses. Experiment 2 confirmed the injection technique in live animals and produced a transient clinical lameness in 4 anesthetized sows injected with amphotericin B (15 mg/mL) in the distal interphalangeal joints of the claw. Clinical lameness was assessed by a categorical lameness scoring system, and a postmortem visual confirmation of joint injection technique was obtained. In Exp. 3, 6 sows were injected with 0, 10, or 15 mg/mL amphotericin B in either the left or right hind foot and were monitored until clinical resolution. Treated sows demonstrated elevated clinical lameness scores. These changes resolved by 7 d after lameness induction. Control sows injected with sterile saline developed a clinical lameness score of 0.5, which resolved 72 h post injection. In Exp. 4, 36 sows were injected with 10 mg/mL amphotericin B in 1 of 4 injection sites (left front claws, right front claws, left rear claws, and right rear claws). All injected sows exhibited a decrease in maximum pressure, stance time, and number of sensors activated on the GaitFour (P < 0.05) sensor system. A static force plate also demonstrated a decrease in weight (kg) being placed on the injected foot when all feet were injected (P ≤ 0.05). Injection of amphotericin B induced a predictable acute lameness that resolved spontaneously and is an effective method to model lameness in sows.

Abstract 658: Pressor And Sympathetic Response To 2% Saline Augmented By Prior Treatment With Intracerebroventricular (icv) Angiotensin II (ANGII)

Previous studies from our laboratory demonstrate that the sensitizing effects of sub-pressor ANGII or aldosterone treatments on ANGII-induced hypertension are mediated through the CNS. The present study tested if pressor response sensitization extends to another hypertensive challenge, 2% saline given as the sole drinking fluid. The study followed an Induction-Delay-Expression ( I-D-E ) experimental design. We instrumented rats with telemetry devices to continuously record blood pressure (BP) and heart rate throughout the experiments. After one week recovery and one week baseline ( B ) recording, rats underwent a second surgery to implant icv cannulas to continuously deliver ANGII (1 ng/kg/min; prior ANGII) or vehicle (control) for one week ( I ). After I and after a 1 week D , drinking water was switched to 2% saline ( E ). The degree of autonomic tone was assessed via ganglionic blockade (hexamethonium, 30 mg/kg, ip) during B , after I , and during E . During B, group BPs were not different (103±2 mmHg control vs. 107±4mmHg, prior-ANGII). Although drinking only 2% saline increased BPs in both groups (122±3 mmHg, control vs. 141±9 mmHg, prior-ANGII), the absolute increase was greater in rats treated with ANGII during I (19±3, control vs. 34±6, prior-ANGII, p<0.05). At B, control and prior-ANGII treated rats showed no difference in the depressor response to hexamethonium (-17±3%, control vs. -13±1%, prior-ANGII) or after I (-13±5%, control vs. -20±9%, prior-ANGII). However, during E while drinking2% saline, prior-ANGII treated rats displayed a significantly larger fall in BP to hexamethonium than controls (-20±5%, control vs. -36±7%, prior-ANGII, p<0.05), suggesting that during E a higher degree of sympathetic tone maintained BP in the prior-ANGII treated rats. These data show that icv treatment with ANGII sensitizes the hypertensive response induced by 2% saline intake and that this enhanced pressor effect is accompanied by elevated sympathetic tone. These results provide new insights into the etiology of salt-sensitive hypertension by implicating a role for ANGII-induced neuroplasticity in CNS systems controlling sympathetic tone.

Abstract 411: Cytokine Receptors in the Subfornical Organ Mediate Sympathetic and Hemodynamic Responses to Peripherally Administered TNF-α and IL-1β in Rat

Introduction: Pro-inflammatory cytokines (PIC) play an important role in regulating autonomic and cardiovascular function in hypertension (HTN) and heart failure (HF). Peripherally administered PIC such as tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) act within the brain to increase blood pressure (BP), heart rate (HR) and renal sympathetic nerve activity (RSNA). These molecules are too big to cross blood brain barrier (BBB), and so the mechanisms by which they activate sympathetic drive to elicit hemodynamic responses remain quite a mystery. Our preliminary data indicate a dense distribution of TNF-α and IL-1β receptors in the subfornical organ (SFO), a forebrain which lacks a BBB and can be accessed readily by circulating PIC. The SFO projects to the hypothalamic paraventricular nucleus, which has been implicated as an important source of cardiovascular and autonomic dysfunction in HTN and HF.

Hypothesis: SFO neurons sense circulating PIC and mediate their effects on sympathetic drive and hemodynamic responses.

Methods: One week after an SFO lesion or a sham lesion (SHAM), urethane anesthetized male SD rats underwent an intracarotid artery (ICA) injection of TNF-α (200 ng) or IL-1β (200 ng). BP (mmHg), HR (beats/min) and RSNA (% change) responses were recorded.

Results: In SHAM rats (n=5), ICA TNF-α dramatically increased (* p<0.05 vs. baseline) the BP (23 ± 1.5*), HR (61 ± 5*) and RSNA (88.5 ± 4.3 %*) responses, which peaked ∼30 min after injection. These early excitatory responses to ICA TNF-α were absent in SFO-lesioned rats (n=5), though a moderate excitatory response occurred hours later. Similarly, ICA IL-1β elicited increases in BP (21.8 ± 2.1*), HR (62 ± 6*) and RSNA (116.5 ± 5.2*) in the SHAM rats (n=5). In the SFO-lesioned rats (n=5), the BP (8.6 ± 1.3 †), HR (24 ± 2 †) and RSNA (26.8 ± 1.6 †) responses to ICA IL-1β were significantly († <0.05 vs. SHAM) attenuated.

Conclusion: These data suggest that the SFO plays an important role as a central nervous system sensor of the peripheral inflammatory state, mediating the effects of circulating PIC on sympathetic drive and cardiovascular function in inflammatory conditions such as HTN and HF. The later occurring excitatory responses to PIC are unexplained but may involve their known vascular effects.

Abstract 417: Central PPAR-γ Activation Attenuates Angiotensin II-Induced Hypertension by Inhibiting Brain Inflammation and Renin-Angiotensin System Activity in Rats

Upregulation of inflammation and renin-angiotensin system (RAS) activity in the brain contributes to hypertension through effects on fluid intake, vasopressin release, and sympathetic nerve activity. Peroxisome proliferator-activated receptor (PPAR)-γ, a nuclear transcription factor, is expressed in key brain areas involved in drinking, vasopressin release and cardiovascular regulation, including the paraventricular nucleus of hypothalamus (PVN). We recently reported that activation of brain PPAR-γ reduced inflammation and RAS activity in the PVN and ameliorated the peripheral manifestations of heart failure. Here we hypothesized that activation of central PPAR-γ might have beneficial effects on angiotensin II (ANG II)-induced hypertension. Spague-Dawley rats received a continuous 2 week subcutaneous infusion of ANG II (120 ng/kg/min), combined with intracerebroventricular infusion of vehicle (VEH) or the PPAR-γ agonist pioglitazone (3 nmoL/h). At 2 weeks, blood pressure (BP) had significantly (*P<0.05) increased (131±3* vs 98±3 mmHg) and the BP response to ganglionic blockade (70±4* vs 43±3 mmHg) was greater in conscious VEH-treated ANG II rats compared with normal (control) rats. Water intake (34±2* vs 25±2 mL) and plasma vasopressin following 4 hours of water restriction (20.79±2.62* vs 10.62±1.27 pg/mL) were increased. PPAR-γ mRNA in the PVN was unchanged in VEH-treated ANG II rats, compared with control rats, but PPAR-γ DNA binding activity (0.05±0.01* vs 0.09±0.01 OD 450nm ) was reduced and mRNA for interleukin-1β (2.76±0.22* vs 1.09±0.21 fold change), tumor necrosis factor-α (1.58±0.09* vs 1.04±0.12 fold change) and ANG II type-1 receptor (1.71±0.15* vs 1.03±0.10 fold change) was augmented. All of these findings were ameliorated (by 24-36%*) in ANG II rats treated with pioglitazone, which increased PPAR-γ mRNA and PPAR-γ DNA binding activity in the PVN (by 73-77%*). The results suggest that activating brain PPAR-γ to reduce central inflammation and RAS activity, thereby suppressing fluid intake, vasopressin release and sympathetic drive, may be a novel approach to the treatment of ANG II-dependent hypertension.

Altered ADAR 2 equilibrium and 5HT(2C) R editing in the prefrontal cortex of ADAR 2 transgenic mice

Modulation of serotonin signaling by RNA editing of the serotonin 2C receptor (5HT(2C) R) may be relevant to affective disorder as serotonin functions regulate mood and behavior. Previously, we observed enhanced endogenous behavioral despair in ADAR2 transgenic mice. As the transcript of the 5HT(2C) R is a substrate of ADAR2, we hypothesized that perturbed ADAR2 equilibrium in the prefrontal cortex of ADAR2 transgenic mice alters the normal distribution of edited amino acid isoforms of the 5HT(2C) R and modifies the receptor function in downstream basal extracellular signal-regulated kinase (ERK) signaling. We examined groups of naive control and ADAR2 transgenic mice and found significantly increased ADAR2 expression, increased RNA editing at A, C, D and E sites and significantly altered normal distribution of edited amino acid isoforms of the 5HT(2C) R with increased proportions of valine asparagine valine, valine serine valine, valine asparagine isoleucine, isoleucine asparagine valine and decreased isoleucine asparagine isoleucine amino acid isoforms of the 5HT(2C) R in ADAR2 transgenic mice. Localized serotonin levels (5-HT) were unchanged and perturbed ADAR2 equilibrium coincides with dysregulated edited amino acid isoforms of the 5HT(2C) R and reduced basal ERK signaling. These results altogether suggest that altered 5HT(2C) R function could be contributing to enhanced depression-like behavior of ADAR2 transgenic mice and further implicate ADAR2 as a contributing factor in cases of affective disorder.

The effect of selection for residual feed intake on general behavioral activity and the occurrence of lesions in Yorkshire gilts

The objectives of this study were to determine the effect of selection for improved residual feed intake on behavior, activity, and lesion scores in gilts in their home pen. A total of 192 gilts were used, 96 from a line that had been selected for decreased residual feed intake over 5 generations (LRFI) and 96 from a randomly bred control line. Gilts were housed in 12 pens (16 gilts/pen; 0.82 m(2)/gilt) containing 8 gilts from each line in a conventional grow-finish unit. Twelve hours of video footage were collected on the day of placement and then every 4 wk for 3 more observational periods. Video was scored using a 10-min instantaneous scan sampling technique for 4 postures (standing, lying, sitting, and locomotion) and 1 behavior (at drinker). Categories of active (standing, locomotion, and at drinker) and inactive (sitting and lying) were also created. Lesion scores were collected 24 h after behavior collection had begun. The body of a gilt was divided into 4 regions, with each region receiving a score of 0 (0 lesions) to 3 (5+ lesions). All statistical analyses used Proc Mixed of SAS. Data were analyzed separately for the day of placement and the subsequent 3 rounds. General activity was summarized on a percentage basis by each posture and behavior and subjected to an arcsine square root transformation to normalize data and stabilize variance. Analysis was performed on each behavior and posture. Lesion scores for each region of the body were analyzed as repeated measures. There were no differences (P > 0.05) between genetic lines for all postures and the behavior at drinker on the day of placement. However, over subsequent rounds it was observed that LRFI gilts spent less (P = 0.03) time standing, more time sitting (P = 0.05), and were less active (P = 0.03) overall. Gilts from the LRFI line had decreased (P < 0.045) lesion scores on the day after placement. However, over subsequent rounds there were no (P > 0.05) differences between the genetic lines. In conclusion, on the day of placement there were no postural, behavior, or general activity differences between genetic lines, but LRFI gilts had decreased lesion scores. Behavioral differences were observed between genetic lines over subsequent rounds, with LRFI gilts becoming less active, but there were no differences in lesion scores.

Performance and carcass characteristics of finishing beef cattle managed in a bedded hoop-barn system

The use of bedded hoop barns in finishing systems for beef cattle has not been widely researched. In this management system, beef cattle are confined to hoop barns throughout finishing, and bedding is used to absorb animal waste, which results in minimal effluent. The objective of this study was to compare the performance and carcass characteristics of finishing beef steers (n = 1,428) managed in a bedded hoop-barn management system vs. an open-feedlot system with shelter. Six feeding trials were conducted over a 3-yr period. Three trials were conducted during summer-fall and 3 trials were conducted during winter-spring. Crossbred steers were allotted to 3 pens in the hoop-barn system and to 3 pens in the open-lot system (approximately 40 steers per pen in both facility systems). Stocking densities for the steers were 4.65 m(2) per steer in the hoop-barn system and 14.7 m(2) per steer in the open-lot system. The steers were begun on trial weighing 410 and 411 kg (SD = 21), were fed for 102.3 and 103.0 d (SD = 3.8), and were weighed off test at 595 and 602 kg (SD = 21) for the hoop-barn and open-lot systems, respectively. Steer performance measures consisted of ADG, DMI, and G:F. Carcass characteristics were HCW, fat thickness, LM area, KPH percentage, marbling score, USDA yield grade, and USDA quality grade. No year, season, or pen (management system) main effects, or season x management system and year x management system interactions were observed for any of the items measured related to cattle performance or carcass characteristics (P > 0.05). Final mud scores (a subjective evaluation of the amount of soil and manure adhering to the hair coat of the animals) were greater for the steers from the open-lot system compared with those from the hoop-barn system (P < 0.02), suggesting steers in the hoop-barn system carried less mud than steers from the open-lot system. Average daily cornstalk bedding use in the hoop-barn system was 2.3 kg/steer during summer-fall and 2.6 kg/steer during winter-spring. The performance of finishing cattle managed in a hoop-barn system was not different from the performance of cattle managed in an open-feedlot system with shelter during summer and winter. Managing beef cattle in hoop barns required more bedding but resulted in decreased mud scores compared with cattle managed in an open-lot system with shelter. Hoop barns are a viable alternative housing management system for finishing beef cattle.

Drinking behavior in nursery pigs: determining the accuracy between an automatic water meter versus human observers

Assimilating accurate behavioral events over a long period can be labor-intensive and relatively expensive. If an automatic device could accurately record the duration and frequency for a given behavioral event, it would be a valuable alternative to the traditional use of human observers for behavioral studies. Therefore, the objective of this study was to determine the accuracy in the time spent at the waterer and the number of visits to the waterer by individually housed nursery pigs between human observers scoring video files using Observer software (OBS) and an automatic water meter Hobo (WM, control) affixed onto the waterline. Eleven PIC USA genotype gilts (22 +/- 2 d of age; 6.5 +/- 1.4 kg of BW) were housed individually in pens with ad libitum access to a corn-based starter ration and one nipple waterer. Behavior was collected on d 0 (day of weaning), 7, and 14 of the trial using 1 color camera positioned over 4 attached pens and a RECO-204 DVR at 1 frame per second. For the OBS method, 2 experienced observers recorded drinking behavior from the video files, which was defined as when the gilt placed her mouth over the nipple waterer. Data were analyzed using nonparametric methods and the general linear model and regression procedures in SAS. The experimental unit was the individual pen housing 1 gilt. The GLM model included the method of observation (WM vs. OBS) and time (24 h) as variables, and the gilt nested within method was used as the error term. Gilts consumed more water (P = 0.04) on d 14 than on d 0. The time of day affected (P < 0.001) the number of visits and the time spent at the waterer regardless of the method. However, the OBS method underestimated (P < 0.001) the number of visits to the waterer (3.48 +/- 0.33 visits/h for OBS vs. 4.94 +/- 0.33 for WM) and overestimated (P < 0.001) the time spent at the waterer (22.6 +/- 1.46 s/h for OBS vs. 13.9 +/- 1.43 for WM) compared with WM. The relationship between the 2 methods for prediction of time spent at the waterer and number of visits made by the gilts was weak (R(2) = 0.56 and 0.69, respectively). Collectively, these data indicate that the use of the traditional OBS method for quantifying drinking behavior in pigs can be misleading. Quantifying drinking behavior and perhaps other behavioral events via the OBS method must be more accurately validated.