A Glutamate Scavenging Protocol Combined with Deanna Protocol in SOD1-G93A Mouse Model of ALS

Amyotrophic lateral sclerosis (ALS) is a progressive disease of neuronal degeneration in the motor cortex, brainstem, and spinal cord, resulting in impaired motor function and premature demise as a result of insufficient respiratory drive. ALS is associated with dysfunctions in neurons, neuroglia, muscle cells, energy metabolism, and glutamate balance. Currently, there is not a widely accepted, effective treatment for this condition. Prior work from our lab has demonstrated the efficacy of supplemental nutrition with the Deanna Protocol (DP). In the present study, we tested the effects of three different treatments in a mouse model of ALS. These treatments were the DP alone, a glutamate scavenging protocol (GSP) alone, and a combination of the two treatments. Outcome measures included body weight, food intake, behavioral assessments, neurological score, and lifespan. Compared to the control group, DP had a significantly slower decline in neurological score, strength, endurance, and coordination, with a trend toward increased lifespan despite a greater loss of weight. GSP had a significantly slower decline in neurological score, strength, endurance, and coordination, with a trend toward increased lifespan. DP+GSP had a significantly slower decline in neurological score with a trend toward increased lifespan, despite a greater loss of weight. While each of the treatment groups fared better than the control group, the combination of the DP+GSP was not better than either of the individual treatments. We conclude that the beneficial effects of the DP and the GSP in this ALS mouse model are distinct, and appear to offer no additional benefit when combined.

Seizures Caused by Exposure to Hyperbaric Oxygen in Rats Can Be Predicted by Early Changes in Electrodermal Activity

Hyperbaric oxygen (HBO₂) is breathed during undersea operations and in hyperbaric medicine. However, breathing HBO₂ by divers and patients increases the risk of central nervous system oxygen toxicity (CNS-OT), which ultimately manifests as sympathetic stimulation producing tachycardia and hypertension, hyperventilation, and ultimately generalized seizures and cardiogenic pulmonary edema. In this study, we have tested the hypothesis that changes in electrodermal activity (EDA), a measure of sympathetic nervous system activation, precedes seizures in rats breathing 5 atmospheres absolute (ATA) HBO₂. Radio telemetry and a rodent tether apparatus were adapted for use inside a sealed hyperbaric chamber. The tethered rat was free to move inside a ventilated animal chamber that was flushed with air or 100% O₂. The animal chamber and hyperbaric chamber (air) were pressurized in parallel at ~1 atmosphere/min. EDA activity was recorded simultaneously with cortical electroencephalogram (EEG) activity, core body temperature, and ambient pressure. We have captured the dynamics of EDA using time-varying spectral analysis of raw EDA (TVSymp), previously developed as a tool for sympathetic tone assessment in humans, adjusted to detect the dynamic changes of EDA in rats that occur prior to onset of CNS-OT seizures. The results show that a significant increase in the amplitude of TVSymp values derived from EDA recordings occurs on average (±SD) 1.9 ± 1.6 min before HBO₂-induced seizures. These results, if corroborated in humans, support the use of changes in TVSymp activity as an early "physio-marker" of impending and potentially fatal seizures in divers and patients.

Exogenous ketone ester delays CNS oxygen toxicity without impairing cognitive and motor performance in male Sprague-Dawley rats

Hyperbaric oxygen (HBO2) is breathing >1 atmosphere absolute (ATA; 101.3 kPa) O2 and is used in HBO2 therapy and undersea medicine. What limits the use of HBO2 is the risk of developing central nervous system (CNS) oxygen toxicity (CNS-OT). A promising therapy for delaying CNS-OT is ketone metabolic therapy either through diet or exogenous ketone ester (KE) supplement. Previous studies indicate that KE induces ketosis and delays the onset of CNS-OT; however, the effects of exogeneous KE on cognition and performance are understudied. Accordingly, we tested the hypothesis that oral gavage with 7.5 g/kg induces ketosis and increases the latency time to seizure (LSz) without impairing cognition and performance. A single oral dose of 7.5 g/kg KE increases systemic β-hydroxybutyrate (BHB) levels within 0.5 h and remains elevated for 4 h. Male rats were separated into three groups: control (no gavage), water-gavage, or KE-gavage, and were subjected to behavioral testing while breathing 1 ATA (101.3 kPa) of air. Testing included the following: DigiGait (DG), light/dark (LD), open field (OF), and novel object recognition (NOR). There were no adverse effects of KE on gait or motor performance (DG), cognition (NOR), and anxiety (LD, OF). In fact, KE had an anxiolytic effect (OF, LD). The LSz during exposure to 5 ATA (506.6 kPa) O2 (≤90 min) increased 307% in KE-treated rats compared with control rats. In addition, KE prevented seizures in some animals. We conclude that 7.5 g/kg is an optimal dose of KE in the male Sprague-Dawley rat model of CNS-OT.

Effects of Cardiac Hormones on Arterial Pressure and Sodium Excretion in NPRA Knockout Mice

These studies were designed to determine if the atria contains natriuretic substances that act through a non–natriuretic peptide type A (NPRA) receptor mechanism. C57BL/6 mice, either wild-type NPRA++ (WT) or NPRA —- knockout (KO), were anesthetized with pentobarbital. Catheters were placed in the trachea, carotid artery, jugular vein, and bladder. Urine was collected for six 30-min periods. Both groups received an iv injection of 100 ng of rat atrial natriuetic peptide (rANP) in 200 μl of saline after the first period (30 mins) and 200 μl of rat atrial extract after the fourth period (120 mins). ANP injection increased urine flow (UF) to 2.7 ± 0.5 μl/min in the WT versus 1.9 ± 0.2 in KO. Extract increased UF to 7.9 ± 1.5 μl/min in WT versus 2.7 ± 0.4 in KO (P < 0.01). ANP increased sodium excretion (ENa) to 0.47 ± 0.10 μmoles/min in WT versus 0.27 ± 0.04 in KO (P < 0.05). Extract increased ENa to 1.44 ± 0.47 μmoles/min in WT versus 0.26 ± 0.06 in KO (P < 0.05). Extract decreased mean arterial pressure (MAP) to 62 ± 3 mm Hg in the WT versus 81 ± 5 in KO (P < 0.01). ENa and MAP responses to extract in KO were not different from responses to 200 μl of saline. A constant 150-min infusion of rat atrial extract increased urine flow by 3-fold and ENa by 5-fold (both P < 0.05) in the WT mice but had no significant effect in the KO mice. Thus, acute renal and MAP responses to atrial extracts require the NPRA receptor.

Metabolic therapy with Deanna Protocol supplementation delays disease progression and extends survival in amyotrophic lateral sclerosis (ALS) mouse model

Amyotrophic Lateral Sclerosis (ALS), also known as Lou Gehrig's disease, is a neurodegenerative disorder of motor neurons causing progressive muscle weakness, paralysis, and eventual death from respiratory failure. There is currently no cure or effective treatment for ALS. Besides motor neuron degeneration, ALS is associated with impaired energy metabolism, which is pathophysiologically linked to mitochondrial dysfunction and glutamate excitotoxicity. The Deanna Protocol (DP) is a metabolic therapy that has been reported to alleviate symptoms in patients with ALS. In this study we hypothesized that alternative fuels in the form of TCA cycle intermediates, specifically arginine-alpha-ketoglutarate (AAKG), the main ingredient of the DP, and the ketogenic diet (KD), would increase motor function and survival in a mouse model of ALS (SOD1-G93A). ALS mice were fed standard rodent diet (SD), KD, or either diets containing a metabolic therapy of the primary ingredients of the DP consisting of AAKG, gamma-aminobutyric acid, Coenzyme Q10, and medium chain triglyceride high in caprylic triglyceride. Assessment of ALS-like pathology was performed using a pre-defined criteria for neurological score, accelerated rotarod test, paw grip endurance test, and grip strength test. Blood glucose, blood beta-hydroxybutyrate, and body weight were also monitored. SD+DP-fed mice exhibited improved neurological score from age 116 to 136 days compared to control mice. KD-fed mice exhibited better motor performance on all motor function tests at 15 and 16 weeks of age compared to controls. SD+DP and KD+DP therapies significantly extended survival time of SOD1-G93A mice by 7.5% (p = 0.001) and 4.2% (p = 0.006), respectively. Sixty-three percent of mice in the KD+DP and 72.7% of the SD+DP group lived past 125 days, while only 9% of the control animals survived past that point. Targeting energy metabolism with metabolic therapy produces a therapeutic effect in ALS mice which may prolong survival and quality of life in ALS patients.

Female rats are more susceptible to central nervous system oxygen toxicity than male rats

Tonic–clonic seizures typify central nervous system oxygen toxicity (CNS‐OT) in humans and animals exposed to high levels of oxygen, as are encountered during scuba diving. We previously demonstrated that high doses of pseudoephedrine (PSE) decrease the latency to seizure (LS) for CNS‐OT in young male rats. This study investigated whether female rats respond similarly to PSE and hyperbaric oxygen (HBO). We implanted 60 virgin stock (VS) and 54 former breeder (FB) female rats with radio‐telemetry devices that measured brain electrical activity. One week later, rats were gavaged with saline or PSE in saline (40, 80, 120, 160, or 320 mg/kg) before diving to five atmospheres absolute in 100% oxygen. The time between reaching maximum pressure and exhibiting seizure was LS. Vaginal smears identified estrus cycle phase. PSE did not decrease LS for VS or FB, primarily because they exhibited low LS for all conditions tested. VS had shorter LS than males at 0, 40, and 80 mg/kg (−42, −49, and −57%, respectively). FB also had shorter LS than males at 0, 40, and 80 mg/kg (−60, −86, and −73%, respectively). FB were older than VS (286 ± 10 days vs. 128 ± 5 days) and weighed more than VS (299 ± 2.7 g vs. 272 ± 2.1 g). Males tested were younger (88 ± 2 days), heavier (340 ± 4.5 g), and gained more weight postoperatively (7.2 ± 1.6 g) than either VS (−0.4 ± 1.5 g) or FB (−1.6 ± 1.5 g); however, LS correlated poorly with age, body mass, change in body mass, and estrus cycle phase. We hypothesize that differences in sex hormones underlie females' higher susceptibility to CNS‐OT than males.

We previously reported that high doses of pseudoephedrine (PSE), a decongestant commonly used by scuba divers, decreases latency to seizure in a male rat model of central nervous system oxygen toxicity (CNS‐OT). We have now found that PSE does not have the same effect in female rats (either virgin stock [VS] or former breeders [FB]), primarily because female rats exhibit an inherently low latency to seizure. This sex difference appears to be independent of age, body mass, and estrus cycle phase.

High doses of pseudoephedrine hydrochloride accelerate onset of CNS oxygen toxicity seizures in unanesthetized rats

Pseudoephedrine (PSE) salts (hydrochloride and sulfate) are commonly used as nasal and paranasal decongestants by scuba divers. Anecdotal reports from the Divers Alert Network suggest that taking PSE prior to diving while breathing pure O₂ increases the risk for CNS oxygen toxicity (CNS-OT), which manifests as seizures. We hypothesized that high doses of PSE reduce the latency time to seizure (LS) in unanesthetized rats breathing 5 atmospheres absolute (ATA) of hyperbaric oxygen. Sixty-three male rats were implanted with radio-transmitters that recorded electroencephalogram activity and body temperature. After ≥7-day recovery, and 2 h before "diving", each rat was administered either saline solution (control) or PSE hydrochloride intragastrically at the following doses (mg PSE/kg): 0, 40, 80, 100, 120, 160, and 320. Rats breathed pure O₂ and were dived to 5ATA until the onset of behavioral seizures coincident with neurological seizures. LS was the time elapsed between reaching 5ATA and exhibiting seizures. We observed a significant dose-dependent decrease in the LS at doses of 100-320 mg/kg, whereas no significant differences in LS from control value were observed at doses ≤80 mg/kg. Our findings showed that high doses of PSE accelerate the onset of CNS-OT seizures in unanesthetized rats breathing 5ATA of poikilocapnic hyperoxia. Extrapolating our findings to humans, we conclude that the recommended daily dose of PSE should not be abused prior to diving with oxygen-enriched gas mixes or pure O₂.

Therapeutic ketosis with ketone ester delays central nervous system oxygen toxicity seizures in rats

Central nervous system oxygen toxicity (CNS-OT) seizures occur with little or no warning, and no effective mitigation strategy has been identified. Ketogenic diets (KD) elevate blood ketones and have successfully treated drug-resistant epilepsy. We hypothesized that a ketone ester given orally as R,S-1,3-butanediol acetoacetate diester (BD-AcAc(2)) would delay CNS-OT seizures in rats breathing hyperbaric oxygen (HBO(2)). Adult male rats (n = 60) were implanted with radiotelemetry units to measure electroencephalogram (EEG). One week postsurgery, rats were administered a single oral dose of BD-AcAc(2), 1,3-butanediol (BD), or water 30 min before being placed into a hyperbaric chamber and pressurized to 5 atmospheres absolute (ATA) O2. Latency to seizure (LS) was measured from the time maximum pressure was reached until the onset of increased EEG activity and tonic-clonic contractions. Blood was drawn at room pressure from an arterial catheter in an additional 18 animals that were administered the same compounds, and levels of glucose, pH, Po(2), Pco(2), β-hydroxybutyrate (BHB), acetoacetate (AcAc), and acetone were analyzed. BD-AcAc(2) caused a rapid (30 min) and sustained (>4 h) elevation of BHB (>3 mM) and AcAc (>3 mM), which exceeded values reported with a KD or starvation. BD-AcAc(2) increased LS by 574 ± 116% compared with control (water) and was due to the effect of AcAc and acetone but not BHB. BD produced ketosis in rats by elevating BHB (>5 mM), but AcAc and acetone remained low or undetectable. BD did not increase LS. In conclusion, acute oral administration of BD-AcAc(2) produced sustained ketosis and significantly delayed CNS-OT seizures by elevating AcAc and acetone.

A potential early physiological marker for CNS oxygen toxicity: hyperoxic hyperpnea precedes seizure in unanesthetized rats breathing hyperbaric oxygen

Hyperbaric oxygen (HBO(2)) stimulates presumptive central CO2-chemoreceptor neurons, increases minute ventilation (V(min)), decreases heart rate (HR) and, if breathed sufficiently long, produces central nervous system oxygen toxicity (CNS-OT; i.e., seizures). The risk of seizures when breathing HBO(2) is variable between individuals and its onset is difficult to predict. We have tested the hypothesis that a predictable pattern of cardiorespiration precedes an impending seizure when breathing HBO2. To test this hypothesis, 27 adult male Sprague-Dawley rats were implanted with radiotelemetry transmitters to assess diaphragmatic/abdominal electromyogram, electrocardiogram, and electroencephalogram. Seven days after surgery, each rat was placed in a sealed, continuously ventilated animal chamber inside a hyperbaric chamber. Both chambers were pressurized in parallel using poikilocapnic 100% O(2) (animal chamber) and air (hyperbaric chamber) to 4, 5, or 6 atmospheres absolute (ATA). Breathing 1 ATA O(2) initially decreased V(min) and HR (Phase 1 of the compound hyperoxic ventilatory response). With continued exposure to normobaric hyperoxia, however, V(min) began increasing toward the end of exposure in one-third of the animals tested. Breathing HBO2 induced an early transient increase in V(min) (Phase 2) and HR during the chamber pressurization, followed by a second significant increase of V(min) ≤8 min prior to seizure (Phase 3). HR, which subsequently decreased during sustained hyperoxia, showed no additional changes prior to seizure. We conclude that hyperoxic hyperpnea (Phase 3 of the compound hyperoxic ventilatory response) is a predictor of an impending seizure while breathing poikilocapnic HBO(2) at rest in unanesthetized rats.

Phenol injury-induced hypertension stimulates proximal tubule Na+/H+ exchanger activity

Injection of 50 microl 10% phenol into rat renal cortex activates renal sympathetic nerve activity which provokes acute hypertension that persists for weeks. We have previously shown with membrane fractionation that phenol injury caused a redistribution of the main proximal tubule (PT) apical transporter NHE3 (Na+/H+ exchanger isoform 3) to low density membranes enriched in apical microvilli. The aim of this study was to determine whether phenol injury increases PT apical Na+/H+ exchanger (NHE) activity. NHE activity was measured in vivo as the initial rate of change in intracellular pH (dpH(i)/dt) during luminal Na+ removal in PT preloaded with the pH-sensitive fluorescence dye BCECF. Injection of 50 microl 10% phenol increased blood pressure from 113 +/- 5.2 to 130 +/- 4.6 mmHg without changing glomerular filtration rate or urine output. NHE activity increased 2.6-fold by 70 min after phenol injury. The increase of NHE activity was accompanied with an increase of tubular reabsorption. Total NHE activity/NHE3 protein in cortical brush-border membrane (BBM) vesicles, measured by acridine orange quench and immunoblot, respectively, was unchanged by phenol injury. In conclusion, acute phenol injury provokes coincident increases in PT apical NHE activity, redistribution of NHE3 into low density apical membranes, and hypertension. The increase in NHE activity may contribute to the lack of pressure-diuresis and the maintenance of chronic hypertension in this model.

CytochromeP-450 metabolites in endothelin-stimulated cardiac hormone secretion

We examined the role of cytochrome P-450-arachidonate (CYP450-AA) metabolites in endothelin-1 (ET-1)-stimulated atrial natriuretic peptide (ANP) and pro-ANP-(1-30) secretion from the heart. 17-Octadecynoic acid (17-ODYA, 10-5M) significantly inhibited ANP secretion stimulated by ET-1 (10-8M) in the isolated perfused rat atria and inhibited pro-ANP-(1-30) secretion stimulated by ET-1 (10-8M) or 20-hydroxyeicosatetraenoic acid in cultured neonatal rat ventricular myocytes (NRVM). In NRVM, 17-ODYA significantly ( P < 0.05) increased secretion of cAMP but had no significant effect on the secretion of cGMP from NRVM. Staurosporine, an inhibitor of protein kinase C, completely blocked the inhibitory action of 17-ODYA, whereas a protein kinase A inhibitor, H-89 (5 × 10-5M), did not significantly attenuate the effects of 17-ODYA. The results show that the inhibitory action of 17-ODYA on ET-1-augmented ANP secretion is mediated through cAMP and suggest that CYP450-AA may play an important role in ET-1-induced cardiac hormone secretion.

Neutralization of proANP (1-30) exacerbates hypertension in the spontaneously hypertensive rat

1. The aim of the present studies was to determine the role of proANP (1-30) in the regulation of arterial pressure. It was hypothesized that blocking endogenous proANP (1-30) would exacerbate the hypertension in susceptible animal models. 2. Pentobarbital-anaesthetized spontaneously hypertensive rats (SHR) were pretreated i.v. with 1.2 mL rabbit serum containing an antibody directed specifically against rat proANP (1-30) (SHR-AB group; n = 7) or an equal volume of normal rabbit serum as a control (SHR-NRS group; n = 5). 3. Following a 1 h equilibration period and two 30 min baseline periods, rats were volume expanded with 3 mL of 6% albumin in Krebs' solution and observed for an additional 3 h to determine the effects of the anti-proANP on arterial pressure. 4. Arterial pressure increased in both groups compared with their own baselines with volume expansion, but was significantly greater in the anti-proANP SHR group compared with the SHR-NRS group throughout the volume expansion period. A maximum difference of 21 mmHg between the anti-proANP SHR group and the NRS-SHR group was observed at 150 min of the study (183 +/- 5 vs 162 +/- 3 mmHg, respectively; P < 0.005. 5. These results suggest a protective role for proANP (1-30) in the SHR model of hypertension.

Reciprocal paracrine pathways link atrial natriuretic peptide and somatostatin secretion in the antrum of the stomach

Atrial natriuretic peptide (ANP) as well as its receptor, NPR-A, have been identified in gastric antral mucosa, suggesting that ANP may act in a paracrine fashion to regulate gastric secretion. In the present study, we have superfused antral mucosal segments obtained from rat stomach to examine the paracrine pathways linking ANP and somatostatin secretion in this region.ANP (0.1 pM to 0.1 microM) caused a concentration-dependent increase in somatostatin secretion (EC(50), 0.3 nM). The somatostatin response to ANP was unaffected by the axonal blocker tetrodotoxin but abolished by addition of the selective NPR-A antagonist, anantin. Anantin alone inhibited somatostatin secretion by 18+/-3% (P<0.005), implying that endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion. Somatostatin (1 pM to 1 microM) caused a concentration-dependent decrease in ANP secretion (EC(50), 0.7 nM) that was abolished by addition of the somatostatin subtype 2 receptor (sst2) antagonist, PRL2903. Neutralization of ambient somatostatin with somatostatin antibody (final dilution 1:200) increased basal ANP secretion by 70+/-8% (P<001), implying that endogenous somatostatin inhibits ANP secretion. We conclude that antral ANP and somatostatin secretion are linked by paracrine feedback pathways: endogenous ANP, acting via the NPR-A receptor, stimulates somatostatin secretion, and endogenous somatostatin, acting via the sst2 receptor, inhibits ANP secretion.

Evidence supporting a physiological role for proANP-(1-30) in the regulation of renal excretion

The experiments, performed in pentobarbital sodium-anesthetized rats, consisted of a 1-h equilibration period followed by two 30-min control periods. Subsequently, synthetic rat pro atrial natriuretic peptide (ANP) [proANP-(1-30)] (n = 8) was given as a bolus of 10 microg in 1 ml of 0.9% saline followed by an infusion at 30 ng/min (20 microl/min) for six additional periods. Control rats (n = 6) received only 0.45% saline in the appropriate volumes. Mean arterial pressure, renal blood flow, and glomerular filtration rate did not change significantly in either group during the proANP-(1-30) infusion. Urine flow and potassium excretion increased approximately 50% in the proANP-(1-30)-infused group only (P < 0.05). Sodium excretion and fractional excretion of sodium, expressed as the change from their own baselines, were significantly increased by the proANP-(1-30) infusion (P < 0.05), whereas cGMP excretion was similar in both groups. These results suggest that the rat sequence of proANP-(1-30) produces a natriuresis in the rat independent of changes in hemodynamics and renal cGMP production. In a second study, rats (n = 8) were prepared as above and pretreated with 0.4 ml iv of rabbit serum containing an antibody directed against proANP-(1-30) (anti-proANP group). The rats were volume expanded with 3 ml of 6% albumin in Krebs and observed for 3 h to determine if the anti-proANP would attenuate the responses to volume expansion. Control rats (n = 7) received 0.4 ml of normal rabbit serum. The elevation in potassium excretion in response to volume expansion was significantly attenuated in the anti-proANP group (P < 0.05). Sodium excretion and urine flow responses also tended to be reduced but not significantly. These results suggest that in the rat, proANP-(1-30) plays a physiological role in regulating renal excretion.

Increased bioactivity of rat atrial extracts: relation to aging and blood pressure regulation

The purpose of this study was to evaluate the possible role of atrial factor(s) in the regulation of cardiovascular homeostasis and their relationship to aging. Rats were anesthetized and received jugular vein, carotid artery, and bilateral ureteral catheterization. After a half-hour equilibration period, the rats received 0.5 ml of atrial extract with a concentration of proANP (atrial natriuretic peptide) of 150 microg/ml prepared from either aged (18-20 month, "aged extract group", n = 12) or young (2-3 month, "young extract group", n = 12) rats. Mean arterial pressure (MAP) and renal function were monitored over five 20-minute periods. The atrial extract caused MAP to fall significantly in the aged extract group (p < .05) but MAP was unchanged in young extract group. There was a significant difference in MAP between the two groups (p < .05). Urine output increased significantly in both groups after extract infusion (p < .05 in both cases). Sodium and potassium excretion showed similar responses. However, the diuresis, natriuresis, and kaliuresis after extract infusion would have been expected to be relatively lower in the aged extract group compared to the young extract group considering the significantly lower MAP in the aged extract group. High performance gel permeation chromatography (HP-GPC) analysis of the atrial extract showed an increased quantity of a large molecular weight C-terminal peptide in atrial extracts from aged rats compared to young rat atria. Plasma levels of ANP and proANP 1-30 both increased significantly after extract infusion in both aged and young groups, and there was no significant difference in ANP concentration between the two groups. However, the concentration of proANP 1-30 was significantly increased in the aged group compared to the young group after extract infusion. These results suggest that changes in the structure or processing of proANP in aging may contribute to the different hemodynamic responses.

Amyloid-beta peptide induced inflammatory reaction is mediated by the cytokines tumor necrosis factor and interleukin-1

A chronic inflammatory response possibly mediated by amyloid-beta (A beta) is believed to be a major factor in the pathology of Alzheimer's disease (AD). Recently, we demonstrated that in vivo administration of A beta produces an inflammatory response and vascular disruption as seen in the brains of AD patients. In an inflammatory response, leukocyte activation and extravasation involves cytokine production. Previous studies have indicated that immune interactions exist between the central nervous system and the peripheral immune mechanisms in AD. Increased levels of interleukin-1 beta (IL-1 beta) have been detected in brain tissue, cerebrospinal fluid, and blood/serum from AD patients. In addition, A beta stimulated the production of tumor necrosis factor-alpha (TNF-alpha) in brain astrocytes and murine monocytes. Using an animal model we investigated the role of the cytokines, TNF-alpha and IL-1 beta, in the A beta-induced inflammatory response. Adult male rats were perfused via an intra-aortic cannula with either A beta alone, interleukin-1 receptor antagonist (IL-1 ra) plus A beta, tumor necrosis factor-binding protein (TNF-bp) plus A beta or sterile saline. Serum analysis for TNF-alpha, IL-1 beta, A beta and NO showed a significant increase in TNF-alpha and A beta but not in IL-1 beta or NO after the injection of A beta. Control values for serum A beta averaged 1.6 ng/ml and in rats injected with A beta, 99.6% of this peptide was removed from the blood within 30 min. The mesenteric arterioles and venules were video recorded for 1-2 h and then processed for electron microscopy (EM). In rats given A beta alone there was extensive vascular disruption, including endothelial and smooth muscle damage with leukocyte adhesion and migration. Animals receiving either IL-1 ra or TNF-bp before A beta showed no in vivo leukocyte extravasation or vascular damage under EM. Therefore, the cytokines TNF-alpha and IL-1 beta seem to mediate the vascular disruption and inflammatory response initiated by A beta. Antagonism of these pro-inflammatory cytokines may offer new avenues for AD therapy.

Alterations in the opioid control of LHRH release from hypothalami isolated from aged male rats

Several lines of evidence have suggested that the opioid control of gonadotropin secretion in the male rat is altered with aging. Because neural control of gonadotropins is mediated through luteinizing hormone releasing hormone (LHRH) secreting neurons, we examined the postulated changes in the opioid control of gonadotropins more directly by studying isolated hypothalamic fragments in vitro. Hypothalami from young (75-90 days) and old (18-20 months) males were examined for their ability to release LHRH when incubated with increasing doses of naloxone in a semi-static culture system. Serum concentrations of testosterone and luteinizing hormone (LH) in the donor animals were both significantly lower in old male rats compared with young males. Basal secretion of LHRH was similar in both age groups. Two-way repeated measures ANOVA indicated that naloxone stimulated a significant dose-dependent increase in the release of LHRH into the media. ANOVA also indicated a significant effect of age. We conclude that the changes in the endogenous opioid systems reported to occur with aging are, in fact, linked to differences in LHRH secretion and thus to differences in the dynamic relationship between testosterone and LH in older male rats.

Alterations in atrial natriuretic peptide (ANP) secretion and renal effects in aging

Aging is associated with hypertension and electrolyte disturbances. The purpose of this study was to determine the effect of aging upon secretion and renal actions of atrial natriuretic peptide (ANP). Rats were anesthetized and received tracheal, jugular vein, carotid artery, and bilateral uretheral catheterization. One set of young (2-3 mo) rats (Group 2, n = 9) and one set of old (18-21 mo) rats (Group 4, n = 7) received bilateral atrial appendectomies. Control young (Group 1, n = 8) and old (Group 3, n = 8) rats received a sham appendectomy. All rats were infused (iv) with 6% albumin in Krebs buffer, sufficient to increase blood volume by 15%. Finally, each rat was injected with ANP (1 microgram/kg). Sodium excretion rate (U(Na+)V) in response to volume expansion was significantly decreased in all groups compared to Group 1 (young control, p < .05). All groups demonstrated a striking increase in U(Na+)V with the ANP injection, but the response was greatest in young control rats when factored by body weight (p < .05). There were no significant differences in MAP between the groups, suggesting that the differences in U(Na+)V observed were not the result of hemodynamic factors. Isolated perfused atria from young (n = 9) and old (n = 8) rats were subjected to stretch and endothelin stimulation (50 nM). Atria from young rats showed a dramatic increase in ANP secretion in response to atrial stretch and a further marked increase in secretion in response to endothelin, whereas both of these responses were markedly attenuated in old rats (p < .05). These results suggested that the secretion and renal effects of ANP are impaired in aging. Changes in secretion and actions of ANP in aging could contribute to the development of hypertension or heart failure.

Opioid inhibition of adrenergic and dopaminergic but not serotonergic stimulation of luteinizing hormone releasing hormone release from immortalized hypothalamic neurons

Opioids are known to have an inhibitory effect on the secretion of luteinizing hormone releasing hormone (LHRH) when administered to whole animals in vivo or when applied to hypothalamic fragments in vitro. Whether opioids have this effect by acting directly on the LHRH secreting neurons or require the mediation of an interneuron is controversial. To examine this question, a clonal cell line derived from a hypothalamic neuron (GT1-7) was perfused and fractions collected every 6 min. Morphine treatment had no effect on basal secretion of LHRH, nor on the spontaneous, pulsatile release of LHRH. Isoproterenol, dopamine, and serotonin all produced significant increments in LHRH secretion. Pretreatment of GT1-7 cells for 2 h with morphine, suppressed the LHRH response to isoproterenol and dopamine but had no apparent effect on serotonin-induced LHRH release. These data indicate that morphine has a direct effect on GT1-7 cells that alters their responsiveness to some, but not all, LHRH secretagogues. These results suggest that, in vivo, the inhibitory effects that opioids have on LHRH release may not require an interneuron.