Increased fragmentation of sleep-wake cycles in the 5XFAD mouse model of Alzheimer's disease.

Sleep perturbations including fragmented sleep with frequent night-time awakenings and daytime naps are common in patients with Alzheimer's disease (AD), and these daily disruptions are a major factor for institutionalization. The objective of this study was to investigate if sleep-wake patterns are altered in 5XFAD mice, a well-characterized double transgenic mouse model of AD which exhibits an early onset of robust AD pathology and memory deficits. These mice have five distinct human mutations in two genes, the amyloid precursor protein (APP) and Presenilin1 (PS1) engineered into two transgenes driven by a neuron-specific promoter (Thy1), and thus develop severe amyloid deposition by 4 months of age. Age-matched (4-6.5 months old) male and female 5XFAD mice were monitored and compared to wild-type littermate controls for multiple sleep traits using a non-invasive, high throughput, automated piezoelectric system which detects breathing and gross body movements to characterize sleep and wake. Sleep-wake patterns were recorded continuously under baseline conditions (undisturbed) for 3 days and after sleep deprivation of 4h, which in mice produces a significant sleep debt and challenge to sleep homeostasis. Under baseline conditions, 5XFAD mice exhibited shorter bout lengths (14% lower values for males and 26% for females) as compared to controls (p<0.001). In females, the 5XFAD mice also showed 12% less total sleep than WT (p<0.01). Bout length reductions were greater during the night (the active phase for mice) than during the day, which does not model the human condition of disrupted sleep at night (the inactive period). However, the overall decrease in bout length suggests increased fragmentation and disruption in sleep consolidation that may be relevant to human sleep. The 5XFAD mice may serve as a useful model for testing therapeutic strategies to improve sleep consolidation in AD patients.

Vasopressin-central nervous system interactions in the development of DOCA hypertension.

DOCA-salt hypertension does not develop in rats with hereditary lack of vasopressin (DI rats) nor in rats with lesion of the anteroventral region of the third ventricle (AV3V), an area controlling vasopressin (VP) release. We examined, therefore, the effect of VP treatment on the development of DOCA salt hypertension in AV3V-lesioned (AV3V-L) normal Sprague-Dawley rats and in Brattleboro rats homozygous for diabetes insipidus (DI rats). We also examined changes in vascular reactivity in isolated, perfused kidneys in the experimental groups. Whereas sham-lesioned (SL) rats showed hypertension at 5 weeks, AV3V-L rats showed no change in arterial pressure (AP) after DOCA. AV3V-L rats given VP exhibited only an intermediate rise in AP in spite of the fact that plasma VP levels were comparable in DOCA-treated SL rats and AV3V-L rats. SL and AV3V-L rats given VP showed enhanced renal vascular activity whereas no vascular changes occurred in AV3V-L rats. At 5 weeks post DOCA, intact DI rats given VP were hypertensive and exhibited enhanced renal vascular reactivity. AV3V lesion in DI rats completely prevented VP-induced DOCA/salt hypertension and enhanced vascular responsiveness. These data suggest that VP plays a primary role in DOCA-salt hypertension through an induction of enhanced vascular reactivity and through central mechanisms requiring the integrity of the AV3V region.

Comparative central and peripheral antihypertensive mechanisms of urapidil and prazosin.

The central effects of urapidil were investigated in conscious rats with sinoaortic denervation. Intraventricular urapidil administration (40 to 100 micrograms) produced a transient depressor response followed by a pressor response coupled with tachycardia. In comparison, intraventricular prazosin administration (2.5 to 5.0 micrograms) produced only a prolonged depressor effect. The effect of intravenously administered urapidil (3 mg/kg) on arterial pressure, heart rate, and mesenteric, renal, and hindquarter resistances was then compared with that of prazosin (0.5 mg/kg) in conscious rats with sinoaortic denervation, instrumented with pulsed Doppler flow probes. Both agents caused similar significant decreases in arterial pressure and vascular resistances, but urapidil decreased renal resistance significantly more than did prazosin. Prazosin increased heart rate, whereas no change was found with urapidil. Prazosin blocked the pressor and regional constrictor effects of intravenously administered norepinephrine more effectively than urapidil.

Evidence that central dopamine receptors modulate sympathetic neuronal activity to the adrenal medulla to alter glucoregulatory mechanisms.

Previous reports suggest that analogs of dopamine (DA) can produce hyperglycemia in rats by interacting with DA receptors. Experiments reported here indicate the site of action and describe the metabolic sequalae associated with the hyperglycemic effect of apomorphine (APO), produced in conscious unrestrained rats. Apomorphine was more potent when administered by intracerebroventricular (i.c.v.) injection than when given subcutaneously (s.c.). Very small doses of the DA receptor antagonist pimozide, given intraventricularly, blocked the hyperglycemic effect of apomorphine administered subcutaneously. Sectioning of the spinal cord at thoracic vertebra T1-2 or sectioning the greater splanchnic nerve blocked apomorphine-induced hyperglycemia; whereas section of the superior colliculus or section at T5-6 had no effect. A dose of apomorphine or epinephrine (EPI) producing a similar degree of hyperglycemia elevated the concentration of EPI in serum to a similar degree, and the increase in EPI in serum preceded the increase in glucose in serum. Fasting animals for 2 or 18 hr had no significant effect on EPI- or apomorphine-induced hyperglycemia despite a reduction (91-93%) of the glycogen content of liver and skeletal muscle during the 18 hr fast. 5-Methoxyindole-2-carboxylic acid (MICA), an inhibitor of gluconeogenesis, blocked EPI- and apomorphine-induced hyperglycemia in rats fasted for 18 hr. However, 5-methoxyindole-2-carboxylic acid was ineffective in blocking hyperglycemia in animals fasted for 2 hr. Changes in insulin or glucagon in serum alone cannot account for the hyperglycemic action of apomorphine. These data demonstrate that apomorphine interacts with central DA receptors located in the hindbrain to activate sympathetic neuronal activity to the adrenal gland which subsequently releases epinephrine to alter homeostasis of glucose. Epinephrine may then, depending on the nutritional status, facilitate glycogenolytic or gluconeogenic processes to produce hyperglycemia.

Synergistic effects of combined converting enzyme inhibition and angiotensin II antagonism on blood pressure in conscious telemetered spontaneously hypertensive rats.

OBJECTIVE: To investigate the chronic effects of combined administration of an angiotensin II receptor antagonist (valsartan) and an angiotensin converting enzyme inhibitor (benazeprilat) on blood pressure and heart rate in conscious telemetered spontaneously hypertensive rats. METHODS: Blood pressure and heart rate were monitored (by radiotelemetry) during 2-week infusions of 0.5-10 mg/kg valsartan per day and 0.5-10 mg/kg benazeprilat per day, alone or in combination, into conscious spontaneously hypertensive rats. Also, responses of blood pressure in conscious spontaneously hypertensive rats to exogenous angiotensin I and II were determined. RESULTS: Synergistic antihypertensive effects were observed when valsartan and benazeprilat were coadministered at submaximal monotherapy doses in the range 0.5-1.5 mg/kg per day. For all combination groups, the area over the curve (mmHg x days) for lowering of blood pressure was significantly greater (synergy) than that predicted from the sum of the monotherapy responses. Combination therapy abrogated pressor responses to angiotensin I more effectively than did comparable doses of the monotherapies. CONCLUSIONS: These results demonstrate that combination therapy aimed at interrupting operation of the renin-angiotensin system simultaneously at multiple sites can prevent the partial escape which occurs during chronic angiotensin converting enzyme inhibitor monotherapy. Furthermore, multiple-site intervention results in a more efficacious antihypertensive response than that achieved with high doses of the individual monotherapies.

Synthesis, resolution, absolute stereochemistry, and enantioselectivity of 3',4'-dihydroxynomifensine.

3',4'-Dihydroxynomifensine, 8-amino-1,2,3,4-tetrahydro-4-(3,4-dihydroxyphenyl)-2-methylisoquinoli ne (1a), is an agonist of dopamine receptors in central and peripheral systems. Since this dopamine receptor agonist bears an asymmetric center at position 4, its synthesis and resolution were undertaken as part of a study directed toward determining the mode of interaction of these agents with the receptor(s). The enantiomers of 3',4'-dihydroxynomifensine are of particular interest, as they provide additional probes of present conceptual models of the dopamine receptor(s). Initial attempts to prepare 1a were inefficient or unsuccessful; instead, an isomeric compound, 1,2,4,5-tetra-hydro-2-(3,4-dihydroxyphenyl)-4- methyl-3H-1,4-benzodiazepine (9), was obtained. For this reason, a new route to 3',4'-dihydroxynomifensine was employed. The racemic dimethoxy intermediate 1d, thus obtained, was resolved. Methoxyl cleavage of the isomers of 1d afforded the enantiomers of 1a. Enantiomeric excess of these antipodes or appropriate derivatives was examined by NMR, CD, and HPLC methods. CD analysis suggests an enantiomeric excess greater than 99%. Determination of the absolute configuration of the enantiomers of 1a was determined by single-crystal X-ray diffractometric analysis. Examination of the isomers in several pharmacological test systems revealed a high degree of enantioselectivity. D-1 dopaminergic activity resides almost exclusively in the S enantiomer. The findings of the study have been employed to suggest an accessory binding site on the dopamine receptor(s) that differs from that advanced earlier. This accessory binding site may be specific for the D-1 subpopulation of dopamine receptors.

Design, synthesis, and biological activity of a peptide mimic of vasopressin.

Our molecular modeling studies suggested that the conformational effects of the "cystine-line" residue Pmp1-Cys6 on the cyclohexapeptide ring of the vasopressin antagonist [Pmp1,D-Phe2,Val4]AVP might be mimicked by substitution of D-aminoadipic acid at position 6 and cyclization of its side-chain carboxyl to the alpha-amine of residue 2. The peptide was prepared with DL-aminoadipic acid, and following cyclization, the two diastereomeric peptides were separated and purified by preparative high-performance liquid chromatography. The structure of each was confirmed by amino acid analysis and fast atom bombardment mass spectrometry. The chirality of the aminoadipic acid residue of each peptide was determined by chiral gas chromatography. The circular dichroism spectrum of each peptide was run and compared with the appropriate agonist and antagonist peptide standards. These peptides demonstrated in vitro poor V2-receptor affinity and an inability to inhibit or stimulate vasopressin-induced adenylate cyclase formation, suggesting that they lack one or more key features of the agonist/antagonist pharmacophore.

2-(Arylalkylamino)adenosin-5'-uronamides: a new class of highly selective adenosine A2 receptor ligands.

The synthesis and receptor-binding profiles at adenosine receptor subtypes for a series of 2-(arylalkylamino)-adenosin-5'-uronamides is described. Halogenated 2-phenethylamino analogues such as 3e show greater than 200-fold selectivity for the A2 receptor subtype on the basis of rat brain receptor binding. The general structure-activity relationship of this series of compounds is discussed both in terms of potency at A2 receptors as well as receptor subtype selectivity. It is possible to introduce a hydrophilic carboxyalkyl substituent to this series such as in CGS 21680A (3h) and still retain good potency and selectivity for A2 receptors. In addition, functional data in a perfused working rat heart model shows that these compounds possess full agonist properties at A2 receptors with 3h having a greater than 1500-fold separation between A2 (coronary vasodilatory) and A1 (negative chronotropic) receptor mediated events.

Highly selective adenosine A2 receptor agonists in a series of N-alkylated 2-aminoadenosines.

A wide variety of 2-substituted aminoadenosines were prepared for comparison with the moderately A2 receptor selective adenosine agonist 2-anilinoadenosine (CV-1808). High selectivity combined with significant affinity at the A2 receptor in rat membranes was observed for those amines bearing a two-carbon chain to which was attached an aryl, heteroaryl, or alicyclic moiety. 2-(2-Phenethylamino)adenosine (3d), a 14-fold A2 selective compound, was modified by introduction of a variety of substituents in the benzene ring and the side chain. Some of these changes led to improved A2 affinity and increased selectivity. Replacement of the phenyl moiety by cyclohexenyl produced a 210-fold selective agonist 3ag (CGS 22989) whereas the cyclohexanyl analogue 3af (CGS 22492) was 530-fold selective at the A2 site. These compounds showed hypotensive activity in rat models over a range of doses without the bradycardia observed with less selective agonists.

Effects of valsartan and hydrochlorothiazide alone and in combination on blood pressure and heart rate in conscious-telemetered spontaneously hypertensive rats (SHR).

The purpose of this study was to examine the effectiveness of combined administration of the angiotensin AT1 receptor antagonist valsartan, with the diuretic hydrochlorothiazide (HCTZ), on blood pressure in conscious spontaneously hypertensive rats (SHR). Both drugs were administered continuously via subcutaneously implanted osmotic minipumps alone or in combination for a period of 2 weeks. Mean arterial pressure and heart rate were monitored throughout the infusion interval by means of chronically-implanted radiotransmitters. Coadministration of a diuretic with valsartan potentiated the blood pressure lowering effect in conscious SHR. Responses varied in magnitude from additive (valsartan at 1 mg/kg/day + hydrochlorothiazide at 3 and 10 mg/kg/day) to synergistic (valsartan at 3 mg/kg/day + hydrochlorothiazide at 10 mg/kg/day). The greater blood pressure lowering seen in SHR receiving combination therapy was associated with only a transient increase in heart rate. A similar potentiation of the antihypertensive effect was seen during coadministration of hydrochlorothiazide (HCTZ) with the angiotensin converting enzyme inhibitor benazeprilat. Additivity was noted with benazeprilat at 1 mg/kg/day + hydrochlorothiazide at 3 mg/kg/day, whereas a higher dose of HCTZ resulted in a synergistic response. These findings suggest that the similar results obtained with angiotensin converting enzyme inhibitors and AT1 receptor antagonists are due to the capacity to which diuretic-induced activation of the renin angiotensin system occurs.

Carotid endarterectomy in a metropolitan community: comparison of results from three institutions.

The hospitalizations of 300 patients who had carotid endarterectomies (CEA) in three different kinds of hospital were analyzed. 100 patients had CEA performed by experienced vascular surgeons in a university hospital (UH), 100 patients had CEA performed by experienced vascular surgeons in private community hospitals (PCH), and 100 patients had CEA performed by senior general surgery residents (GSR) assisted by experienced vascular surgeons in a university-affiliated Veterans Administration hospital (VA). Analysis of patient characteristics revealed that, compared with the other groups, VA patients were (1) younger (62 +/- 7 years; p less than 0.001); (2) had a higher frequency of peripheral vascular operations (51%; p less than 0.01; (3) were more often cigarette smokers (84%; p less than 0.001); and (4) had more contralateral carotid occlusions (19%) and ulcerated lesions (73%) (p less than 0.01). GSR had longer operating room times and cerebral ischemia times during shunt insertion and removal (6 +/- 2.8 minutes) and during the CEA (30 +/- 27 minutes) (p less than 0.001). Postoperative hypertension and neck hematomas were less common in PCH patients (p less than 0.001) than in the other groups. Although their duration of hospitalization (17 +/- 12 days) was longer, the VA patients experienced no increased morbidity. There was a high rate of cranial nerve injury in all groups (27%, 15%, 17%) but symptoms were not often permanent (9%, 6%, 6%). Our data indicate that results of vascular operations performed by well-supervised residents are comparable in all important respects to those performed by fully trained surgeons.

The cardiovascular effects of centrally and peripherally administered indoramin in conscious rats.

Indoramin has centrally mediated hypotensive effects in anesthetized animals. In the present study, the cardiovascular effect of central and peripheral indoramin was determined in conscious, freely moving rats. Animals were instrumented with femoral arterial and venous catheters and miniaturized pulsed-Doppler flow probes were placed on the superior mesenteric and renal arteries and lower abdominal aorta. Injection of indoramin (25-100 micrograms) in the lateral cerebroventricle produced an immediate (1.5 min) increase in arterial pressure which was accompanied by vasoconstriction in all three vascular beds. By 10 min all values had returned to control except for heart rate which was decreased. Vehicle alone or intravenous indoramin (100 micrograms) had no effect. In baroreceptor-denervated rats smaller effects were seen. Intravenous indoramin (3.0-13.5 mg/kg) produced dose-related decreases in arterial pressure, heart rate, and hindquarter vascular resistance. The 13.5 mg/kg dose blocked to a similar degree the cardiovascular effect produced by intravenous norepinephrine or stimulation of the paraventricular nucleus. These data suggest that indoramin is an effective peripheral alpha-adrenergic receptor antagonist but does not appear to be centrally active as a hypotensive agent.

Beneficial effects of combined thromboxane synthase inhibition/receptor blockade with CGS 22652 in a canine model of coronary thrombosis.

Various antiplatelet agents were examined for their effectiveness as adjuncts to thrombolytic therapy in a canine model of thrombin-induced coronary thrombosis. Aspirin (5 mg/kg i.v. bolus), CGS 15435A (thromboxane synthase inhibitor (TxSI), 0.1 mg/kg i.v. bolus +0.04 mg/kg per h) and BM 13.505 (thromboxane receptor antagonist (TxRA), 0.5 mg/kg i.v. bolus +0.2 mg/kg per h) administered concurrently with streptokinase (750,000 units/h) were examined for their effects on reperfusion and reocclusion, as were a combination therapy with CGS 15435A + BM 13.505 or the dual TxRA/TxSI inhibitor, CGS 22652 (1 mg/kg i.v. bolus +0.4 mg/kg per h). All dogs received heparin (150 U/kg bolus + 50 U/kg per h) throughout the experimental protocol. Survival analysis at reperfusion indicated that thrombolysis was significantly improved in dogs treated with CGS 15435A, BM 13.505, CGS 15435A+BM 13.505 or CGS 22652 over that of vehicle-treated animals. Both dual inhibitor groups and the BM 13.505 group were significantly different from aspirin. Aspirin-treated dogs were not different from vehicle. Otherwise, all treatments differed from the vehicle-treated group at reocclusion. Time and incidence of reocclusion for CGS 22652 was significantly improved over that of BM 13.505. Residual thrombus weight was significantly reduced in the CGS 22652-treated and BM 13.505 + CGS 15435A-treated animals. These findings demonstrate that streptokinase-induced thrombolysis is accompanied by TxA2/prostaglandin H2 synthesis and platelet activation and suggest a role for platelet activation during reocclusion following clot lysis. These studies also show it is possible to combine the beneficial effects of both a TxRA and TxSI into a single chemical entity, CGS 22652, which, when administered as adjunctive therapy to streptokinase, results in an apparent synergistic antithrombotic effect.

Dopaminergic mediation of the diuretic and natriuretic effects of ANF in the rat.

Atrial natriuretic factor (ANF) increases sodium (Na+) and water excretion 8-10 fold on repeated administration to anesthetized rats. SCH-23390 (80 micrograms/kg i.v.) and R-sulpiride (80 micrograms/kg i.v.), selective antagonists of dopamine receptors in the renal vasculature, inhibited diuresis and natriuresis induced by AP III and dopamine. These findings suggest that ANF exerts its effects on renal Na+ and water handling via a dopaminergic mechanism; however, changes in intrarenal hemodynamics secondary to dopamine receptor blockade may attenuate the actions of ANF.

Popliteal artery injury complicating arthroscopic menisectomy.

Inadvertent popliteal artery injury during arthroscopic menisectomy is an unusual occurrence. Prompt diagnosis and treatment are essential to achieve a good outcome, as illustrated in two of the five patients described herein. Pitfalls in diagnosis led to late recognition and therapy in three patients, with subsequent serious complications; namely, arteriovenous fistula, false aneurysm, and amputation. On the basis of this limited but poignant experience, we propose an outline of steps in management to help others avoid similar problems. If popliteal injury is suspected, we advise exploration immediately to avoid a potential limb-loss crisis. Heparin should be given as soon as diagnosis is made. A posterior incision in the knee crease, rather than the conventional medial approach, gives expedient exposure for precise repair. We also advise passing a no. 3 thrombectomy catheter distally to rule out or retrieve any clot that may have embolized. A completion angiogram is also helpful. Compartment pressure may be measured, but if any doubt exists, a three-compartment fasciotomy should be performed.

Autologous blood retrieval in thoracic, cardiovascular, and orthopedic surgery.

A significant amount of red blood cells were conserved with use of the Cell Saver in cardiac surgery patients and in some orthopedic and vascular surgery patients. No major complications have been associated with its use in our cases. Our results are similar to those of others who have reported on the use of this device. In the cardiac surgery patients we observed significant serum protein losses which had to be replaced. We recommend the use of intraoperative albumin to help maintain adequate urinary output and hemodynamic stability.

Surgical complications with the cochlear multiple-channel intracochlear implant: experience at Hannover and Melbourne.

The surgical complications for the first 153 multiple-channel cochlear implant operations carried out at the Medizinische Hochschule in Hannover and the first 100 operations at the University of Melbourne Clinic, The Royal Victorian Eye and Ear Hospital, are presented. In the Hannover experience the major complications were wound breakdown, wound infection, electrode tie erosion through the external auditory canal, electrode slippage, a persistent increase in tinnitus, and facial nerve stimulation. The incidence of wound breakdown requiring removal of the package was 0.6% in Hannover and 1.0% in Melbourne. The complications for the operation at both clinics were at acceptable levels. It was considered that wound breakdown requiring implant removal could be kept to a minimum by making a generous incision and suturing the flap without tension.

Banded intracochlear electrode array: evaluation of insertion trauma in human temporal bones.

A banded free-fit scala tympani array was inserted into the basal turn of nine human cochleas to evaluate the trauma produced by the procedure. These nine cochleas, together with five nonimplanted controls, were serially sectioned and examined microscopically for damage to the membranous labyrinth, in particular the spiral ligament, the basilar and Reissner's membranes, the stria vascularis, and the osseous spiral lamina. The severity and location of any trauma along the cochlear spiral were recorded. The results indicate that the insertion of the banded scala tympani array resulted in minimal mechanical damage, occurring primarily to a localized region of the spiral ligament. This would not result in significant neural degeneration, and therefore would not compromise the efficacy of the multichannel cochlear prosthesis.

Surgery for an improved multiple-channel cochlear implant.

An improved multiple-channel cochlear implant has been developed. The titanium container with enclosed electronics, the receiver coil, and the connector are embedded in medical-grade Silastic. The upper half of the implant has a diameter of 35 mm and a height of 4.5 mm, and the lower half a diameter of 23 mm and a height of 5 mm. The electrode array has also been designed to reduce the possibility of breakage due to repeated movements over many years. The surgery involves drilling a bed in the mastoid bone for the receiver-stimulator, and fixing the proximal electrode under the mastoid cortex. Gentle insertion of the electrode array through the round window and along the scala tympani is achieved with a specially designed microclaw .

PKPD modelling of the interrelationship between mean arterial BP, cardiac output and total peripheral resistance in conscious rats.

BACKGROUND AND PURPOSE: The homeostatic control of arterial BP is well understood with changes in BP resulting from changes in cardiac output (CO) and/or total peripheral resistance (TPR). A mechanism-based and quantitative analysis of drug effects on this interrelationship could provide a basis for the prediction of drug effects on BP. Hence, we aimed to develop a mechanism-based pharmacokinetic-pharmacodynamic (PKPD) model in rats that could be used to characterize the effects of cardiovascular drugs with different mechanisms of action (MoA) on the interrelationship between BP, CO and TPR. EXPERIMENTAL APPROACH: The cardiovascular effects of six drugs with diverse MoA, (amlodipine, fasudil, enalapril, propranolol, hydrochlorothiazide and prazosin) were characterized in spontaneously hypertensive rats. The rats were chronically instrumented with ascending aortic flow probes and/or aortic catheters/radiotransmitters for continuous recording of CO and/or BP. Data were analysed in conjunction with independent information on the time course of drug concentration using a mechanism-based PKPD modelling approach. KEY RESULTS: By simultaneous analysis of the effects of six different compounds, the dynamics of the interrelationship between BP, CO and TPR were quantified. System-specific parameters could be distinguished from drug-specific parameters indicating that the model developed is drug-independent. CONCLUSIONS AND IMPLICATIONS: A system-specific model characterizing the interrelationship between BP, CO and TPR was obtained, which can be used to quantify and predict the cardiovascular effects of a drug and to elucidate the MoA for novel compounds. Ultimately, the proposed PKPD model could be used to predict the effects of a particular drug on BP in humans based on preclinical data.