Effects of vatinoxan on cardiorespiratory function, fecal output and plasma drug concentrations in horses anesthetized with isoflurane and infusion of medetomidine

A constant rate infusion (CRI) of medetomidine is used to balance equine inhalation anesthesia, but its cardiovascular side effects are a concern. This experimental crossover study aimed to evaluate the effects of vatinoxan (a peripheral α2-adrenoceptor antagonist) on cardiorespiratory and gastrointestinal function in anesthetized healthy horses. Six horses received medetomidine hydrochloride 7μg/kg IV alone (MED) or with vatinoxan hydrochloride 140μg/kg IV (MED+V). Anesthesia was induced with midazolam and ketamine and maintained with isoflurane and medetomidine CRI for 60min. Heart rate, carotid and pulmonary arterial pressures, central venous pressure, cardiac output and arterial and mixed venous blood gases were measured. Selected cardiopulmonary parameters were calculated. Plasma drug concentrations were determined. Fecal output was measured over 24h. For statistical comparisons, repeated measures analysis of covariance and paired t-tests were applied. Heart rate decreased slightly from baseline in the MED group. Arterial blood pressures decreased with both treatments, but significantly more dobutamine was needed to maintain normotension with MED+V (P=0.018). Cardiac index (CI) and oxygen delivery index (DO₂I) decreased significantly more with MED, with the largest difference observed at 20min: CI was 39±2 and 73±18 (P=0.009) and DO₂I 7.4±1.2 and 15.3±4.8 (P=0.014)mL/min/kg with MED and MED+V, respectively. Fecal output or plasma concentrations of dexmedetomidine did not differ between the treatments. In conclusion, premedication with vatinoxan induced hypotension, thus its use in anesthetized horses warrants further studies. Even though heart rate and arterial blood pressures remained clinically acceptable with MED, cardiac performance and oxygen delivery were lower than with MED+V.

Effects of vatinoxan on cardiorespiratory function and gastrointestinal motility during constant-rate medetomidine infusion in standing horses

Background

Medetomidine suppresses cardiovascular function and reduces gastrointestinal motility in horses mainly through peripheral α₂‐adrenoceptors. Vatinoxan, a peripheral α₂‐antagonist, has been shown experimentally to alleviate the adverse effects of some α₂‐agonists in horses. However, vatinoxan has not been investigated during constant‐rate infusion (CRI) of medetomidine in standing horses.

Objectives

To evaluate effects of vatinoxan on cardiovascular function, gastrointestinal motility and on sedation level during CRI of medetomidine.

Study design

Experimental, randomised, blinded, cross‐over study.

Methods

Six healthy horses were given medetomidine hydrochloride, 7 μg/kg i.v., without (MED) and with (MED+V) vatinoxan hydrochloride, 140 μg/kg i.v., followed by CRI of medetomidine at 3.5 μg/kg/h for 60 min. Cardiorespiratory variables were recorded and borborygmi and sedation levels were scored for 120 min. Plasma drug concentrations were measured. The data were analysed using repeated measures ANCOVA and paired t‐tests as appropriate.

Results

Initially heart rate (HR) was significantly lower and mean arterial blood pressure (MAP) significantly higher with MED compared with MED+V. For example at 10 min HR (mean ± s.d.) was 26 ± 2 and 31 ± 5 beats/minute (P = 0.04) and MAP 129 ± 15 and 103 ± 13 mmHg (P<0.001) respectively. At 10 min, cardiac index was lower (P = 0.02) and systemic vascular resistance higher (P = 0.001) with MED than with MED+V. Borborygmi were reduced after MED; this effect was attenuated by vatinoxan (P<0.001). All horses were sedated with medetomidine, but the mean sedation scores were reduced with MED+V until 20 min (6.8 ± 0.8 and 4.5 ± 1.5 with MED and MED+V, respectively, at 10 min, P = 0.001). Plasma concentration of dexmedetomidine was significantly lower in the presence of vatinoxan (P = 0.01).

Main limitations

Experimental study with healthy, unstimulated animals.

Conclusions

Vatinoxan administered i.v. with a loading dose of medetomidine improved cardiovascular function and gastrointestinal motility during medetomidine CRI in healthy horses. Sedation was slightly yet significantly reduced during the first 20 min..

The Summary is available in Portuguese – see Supporting Information

Experimental evolution gone wild

Because of their large population sizes and rapid cell division rates, marine microbes have, or can generate, ample variation to fuel evolution over a few weeks or months, and subsequently have the potential to evolve in response to global change. Here we measure evolution in the marine diatom Skeletonema marinoi evolved in a natural plankton community in CO2-enriched mesocosms deployed in situ. Mesocosm enclosures are typically used to study how the species composition and biogeochemistry of marine communities respond to environmental shifts, but have not been used for experimental evolution to date. Using this approach, we detect a large evolutionary response to CO2 enrichment in a focal marine diatom, where population growth rate increased by 1.3-fold in high CO2-evolved lineages. This study opens an exciting new possibility of carrying out in situ evolution experiments to understand how marine microbial communities evolve in response to environmental change.

Involvement of the first transmembrane segment of human α(2) -adrenoceptors in the subtype-selective binding of chlorpromazine, spiperone and spiroxatrine

BACKGROUND AND PURPOSE

Some large antagonist ligands (ARC239, chlorpromazine, prazosin, spiperone, spiroxatrine) bind to the human α(2A) -adrenoceptor with 10- to 100-fold lower affinity than to the α(2B)- and α(2C)-adrenoceptor subtypes. Previous mutagenesis studies have not explained this subtype selectivity.

EXPERIMENTAL APPROACH

The possible involvement of the extracellular amino terminus and transmembrane domain 1 (TM1) in subtype selectivity was elucidated with eight chimaeric receptors: six where TM1 and the N-terminus were exchanged between the α(2)-adrenoceptor subtypes and two where only TM1 was exchanged. Receptors were expressed in CHO cells and tested for ligand binding with nine chemically diverse antagonist ligands. For purposes of interpretation, molecular models of the three human α(2)-adrenoceptors were constructed based on the β(2)-adrenoceptor crystal structure.

KEY RESULTS

The affinities of three antagonists (spiperone, spiroxatrine and chlorpromazine) were significantly improved by TM1 substitutions of the α(2A)-adrenoceptor, but reciprocal effects were not seen for chimaeric receptors based on α(2B)- and α(2C)-adrenoceptors. Molecular docking of these ligands suggested that binding occurs in the orthosteric ligand binding pocket.

CONCLUSIONS AND IMPLICATIONS

TM1 is involved in determining the low affinity of some antagonist ligands at the human α(2A)-adrenoceptor. The exact mechanism is not known, but the position of TM1 at a large distance from the binding pocket indicates that TM1 does not participate in specific side-chain interactions with amino acids within the binding pocket of the receptor or with ligands bound therein. Instead, molecular models suggest that TM1 has indirect conformational effects related to the charge distribution or overall shape of the binding pocket.

Dexmedetomidine inhibits gastric emptying and oro-caecal transit in healthy volunteers

BACKGROUND

Dexmedetomidine is a potent and selective α2-adrenoceptor agonist used for perioperative and intensive care sedation with certain beneficial qualities. However, based on preclinical observations, it might inhibit gastric emptying and gastrointestinal transit, which could result in unwanted effects in intensive care patients. This study evaluated the effects of dexmedetomidine on gastric emptying and oro-caecal transit time in healthy volunteers.

METHODS

Twelve healthy male subjects were given 1 µg kg(-1) of dexmedetomidine i.v. over 20 min followed by a continuous i.v. infusion of 0.7 µg kg(-1) h(-1) for 190 min. For comparison, subjects were also given 0.10 mg kg(-1) of morphine hydrochloride i.v. over 20 min and a placebo infusion in a randomized order. Gastric emptying was assessed with the paracetamol absorption test and oro-caecal transit time with the hydrogen breath test.

RESULTS

The time to maximum paracetamol concentration in plasma was significantly longer, maximum paracetamol concentration was significantly lower, the area under the plasma paracetamol concentration-time curve was significantly smaller, and oro-caecal transit time was significantly longer during dexmedetomidine infusion compared with morphine or placebo infusion.

CONCLUSIONS

Dexmedetomidine markedly inhibits gastric emptying and gastrointestinal transit in healthy volunteers.

Follow-up of [11C]PIB uptake and brain volume in patients with Alzheimer disease and controls

OBJECTIVE

In Alzheimer disease (AD), the accumulation pattern of beta-amyloid over time and its relationship with dementia severity are unclear. We investigated the brain uptake of the amyloid ligand (11)C-labeled Pittsburgh compound B ([(11)C]PIB) and volumetric brain changes over a 2-year follow-up in patients with AD and in aged healthy controls.

METHODS

Fourteen patients with AD (mean age 72 years, SD 6.6) and 13 healthy controls (mean age 68 years, SD 5.4) were examined at baseline and after 2 years (patients with AD: mean 2.0 years, SD 0.2; controls: mean 2.1 years, SD 0.6) with [(11)C]PIB PET, MRI, and neuropsychological assessments. [(11)C]PIB uptake was analyzed with a voxel-based statistical method (SPM), and quantitative data were obtained with automated region-of-interest analysis. MRI data were analyzed with voxel-wise tensor-based morphometry.

RESULTS

The [(11)C]PIB uptake of the patients with AD did not increase significantly during follow-up when compared with that of the controls. MRI showed progressive brain volume change in the patients with AD, e.g., in the hippocampal region, temporal cortex, and precuneus (p < 0.05). The mean Mini-Mental State Examination score of the patients with AD declined from 24.3 (SD 3.1) at baseline to 21.6 (SD 3.9) at follow-up (p = 0.009). Cognitive decline was also evident in other neuropsychological test results. Baseline neocortical [(11)C]PIB uptake ratios predicted subsequent volumetric brain changes in the controls (r = 0.725, p = 0.005).

CONCLUSIONS

The results suggest no (or only little) increase in (11)C-labeled Pittsburgh compound B ([(11)C]PIB) uptake during 2 years of Alzheimer disease progression, despite advancing brain atrophy and declining cognitive performance. Nevertheless, changes in [(11)C]PIB uptake during a longer follow-up cannot be excluded. High cortical [(11)C]PIB uptake may predict ongoing brain atrophy in cognitively normal individuals.

The diet board: welfare impacts of a novel method of dietary restriction in laboratory rats

Laboratory rats are commonly fed ad libitum (AL). Moderate dietary restriction (DR) decreases mortality and morbidity when compared with AL feeding, but there are several obstacles to the implementation of DR. Traditional methods of restricted feeding disrupt normal diurnal eating rhythms and are not compatible with group housing. We have designed a novel method, the diet board, to restrict the feeding of group-housed rats. Animals fed from the diet board had 15% lower body weight than the AL-fed animals at the age of 17 weeks. The welfare effects of diet board feeding were assessed by comparing the stress physiology of diet board fed animals with that of AL-fed animals. Diet board feeding was associated with higher serum corticosterone levels and lower faecal secretion of IgA, suggesting the diet board causes a stress reaction. However, the AL-fed group had larger adrenal glands with higher adrenaline and noradrenaline content than the diet board animals. No gastric ulcers were found in any of the animals at necropsy. The diet board thus appears to cause a stress reaction when compared with AL-fed rats, but no apparent pathology was associated with this reaction. The diet board could help to solve the health problems associated with AL feeding, while allowing the rats to be group-housed and to maintain their normal diurnal eating rhythms. The diet board can also be seen as a functional cage furniture item, dividing the cage into compartments and thus increasing the structural complexity of the environment. In conclusion, the diet board appears to possess refinement potential compared with traditional methods of DR.

Assessment of MAO-B occupancy in the brain with PET and [11C]-L-deprenyl-D2: a dose-finding study with a novel MAO-B inhibitor, EVT 301

Inhibition of monoamine oxidase type B (MAO-B) activity in the brain is a putative strategy for the treatment of Alzheimer's disease (AD). We performed a dose-selection and validation study of a novel, reversible MAO-B inhibitor, EVT 301. Sixteen healthy volunteers received selegiline (10 mg) or EVT 301 (25, 75, or 150 mg) daily for 7-8 days, and four subjects with AD received 75 mg of EVT 301. MAO-B occupancy in the brain was assessed using positron emission tomography (PET) with [11C]-L-deprenyl-D2. EVT 301 was found to dose-dependently occupy MAO-B in the human brain, with occupancy ranging from 58-78% at a dose of 25 mg to 73-90% at a dose of 150 mg. The corresponding occupancy after selegiline was 77-92%. Determination of MAO-B inhibition in blood platelets underestimated the actual brain occupancy achieved with EVT 301. A daily EVT 301 dose of 75 or 150 mg appears suitable for clinical efficacy studies in patients with AD.

Effects of feedborne fusarium mycotoxins on brain regional neurochemistry of turkeys

An experiment was conducted to investigate the effects of feeding grains naturally contaminated with Fusarium mycotoxins on brain regional neurochemistry of turkeys. The possible preventative effect of a poly-meric glucomannan mycotoxin adsorbent (GMA) was also determined. Forty-five 1-d-old male turkey poults were fed wheat-, corn-, and soybean meal-based diets up to wk 6, formulated with control grains, contaminated grains, or contaminated grains + 0.2% GMA. Deoxynivalenol was the major contaminant, and the concentrations were 2.2 and 3.3 mg/kg of feed during starter and grower phases, respectively. Concentrations of brain monoamine neurotransmitters and metabolites were measured in discrete regions of the brain including the pons, hypothalamus, and cortex by HPLC with electrochemical detection. Neurotransmitters and metabolites analyzed included norepinephrine, dopamine, 3,4-dihydroxyphenylacetic acid, serotonin (5-hydroxytryptamine, 5-HT), and 5-hydroxyindoleacetic acid (5-HIAA). The concentration of 5-HIAA and the 5-HIAA:5-HT-ratio were significantly decreased in pons after feeding contaminated grains. Dietary supplementation with GMA prevented these effects. In the pons, a significant positive correlation (r = 0.52, P < 0.05) was observed between the concentration of 5-HT and BW gain after feeding contaminated diets. The feeding of contaminated diet had no significant effects on the concentrations of neurotransmitters and metabolites in hypothalamus and cortex. It was concluded that consumption of grains naturally contaminated with Fusarium mycotoxins adversely altered the pons serotonergic system of turkeys. Supplementation with GMA partially inhibited these effects.

alpha2A-adrenoceptor antagonism increases insulin secretion and synergistically augments the insulinotropic effect of glibenclamide in mice

BACKGROUND AND PURPOSE

The imidazoline-type alpha2-adrenoceptor antagonists (+/-)-efaroxan and phentolamine increase insulin secretion and reduce blood glucose levels. It is not known whether they act by antagonizing pancreatic beta-cell alpha2-adrenoceptors or by alpha2-adrenoceptor-independent mechanisms. Many imidazolines inhibit the pancreatic beta-cell KATP channel, which is the molecular target of sulphonylurea drugs used in the treatment of type II diabetes. To investigate the mechanisms of action of (+/-)-efaroxan and phentolamine, alpha2A-adrenoceptor knockout (alpha2A-KO) mice were used.

EXPERIMENTAL APPROACH

Effects of (+/-)-efaroxan, 5 mg kg(-1), and phentolamine, 1 mg kg(-1), on blood glucose and insulin levels were compared with those of the non-imidazoline alpha2-adrenoceptor antagonist [8aR,12aS,13aS]-5,8,8a,9,10,11,12,12a,13,13a-decahydro-3-methoxy-12-(ethylsulphonyl)-6H-isoquino[2,1-g][1,6]naphthyridine (RS79948-197), 1 mg kg(-1), and the sulphonylurea glibenclamide, in alpha2A-KO and control (wild type (WT)) mice.

KEY RESULTS

In fed WT mice, (+/-)-efaroxan, phentolamine and RS79948-197 reduced blood glucose and increased insulin levels. Fasting abolished these effects. In fed alpha2A-KO mice, (+/-)-efaroxan, phentolamine and RS79948-197 did not alter blood glucose or insulin levels, and in fasted alpha2A-KO mice, blood glucose levels were increased. Glibenclamide, at a dose only moderately efficacious in WT mice (5 mg kg(-1)), caused severe hyperinsulinaemia and hypoglycaemia in alpha2A-KO mice. This was mimicked in WT mice by co-administration of RS79948-197 with glibenclamide.

CONCLUSIONS AND IMPLICATIONS

These results suggest that (+/-)-efaroxan and phentolamine increase insulin secretion by inhibition of beta-cell alpha2A-adrenoceptors, and demonstrate a critical role for alpha2A-adrenoceptors in limiting sulphonylurea-induced hyperinsulinaemia and hypoglycaemia.

Electroencephalogram spindle activity during dexmedetomidine sedation and physiological sleep

BACKGROUND

Dexmedetomidine, a selective alpha(2)-adrenoceptor agonist, induces a unique, sleep-like state of sedation. The objective of the present work was to study human electroencephalogram (EEG) sleep spindles during dexmedetomidine sedation and compare them with spindles during normal physiological sleep, to test the hypothesis that dexmedetomidine exerts its effects via normal sleep-promoting pathways.

METHODS

EEG was continuously recorded from a bipolar frontopolar-laterofrontal derivation with Entropy Module (GE Healthcare) during light and deep dexmedetomidine sedation (target-controlled infusions set at 0.5 and 3.2 ng/ml) in 11 healthy subjects, and during physiological sleep in 10 healthy control subjects. Sleep spindles were visually scored and quantitatively analyzed for density, duration, amplitude (band-pass filtering) and frequency content (matching pursuit approach), and compared between the two groups.

RESULTS

In visual analysis, EEG activity during dexmedetomidine sedation was similar to physiological stage 2 (S2) sleep with slight to moderate amount of slow-wave activity and abundant sleep spindle activity. In quantitative EEG analyses, sleep spindles were similar during dexmedetomidine sedation and normal sleep. No statistically significant differences were found in spindle density, amplitude or frequency content, but the spindles during dexmedetomidine sedation had longer duration (mean 1.11 s, SD 0.14 s) than spindles in normal sleep (mean 0.88 s, SD 0.14 s; P=0.0014).

CONCLUSIONS

Analysis of sleep spindles shows that dexmedetomidine produces a state closely resembling physiological S2 sleep in humans, which gives further support to earlier experimental evidence for activation of normal non-rapid eye movement sleep-promoting pathways by this sedative agent.

The second extracellular loop of alpha2A-adrenoceptors contributes to the binding of yohimbine analogues

BACKGROUND AND PURPOSE

Rodent alpha(2A)-adrenoceptors bind the classical alpha(2)-antagonists yohimbine and rauwolscine with lower affinity than the human alpha(2A)-adrenoceptor. A serine-cysteine difference in the fifth transmembrane helix (TM; position 5.43) partially explains this, but all determinants of the interspecies binding selectivity are not known. Molecular models of alpha(2A)-adrenoceptors suggest that the second extracellular loop (XL2) folds above the binding cavity and may participate in antagonist binding.

EXPERIMENTAL APPROACH

Amino acids facing the binding cavity were identified using molecular models: side chains of residues 5.43 in TM5 and xl2.49 and xl2.51 in XL2 differ between the mouse and human receptors. Reciprocal mutations were made in mouse and human alpha(2A)-adrenoceptors at positions 5.43, xl2.49 and xl2.51, and tested with a set of thirteen chemically diverse ligands in competition binding assays.

KEY RESULTS

Reciprocal effects on the binding of yohimbine and rauwolscine in human and mouse alpha(2A)-adrenoceptors were observed for mutations at 5.43, xl2.49 and xl2.51. The binding profile of RS-79948-197 was reversed only by the XL2 substitutions.

CONCLUSIONS AND IMPLICATIONS

Positions 5.43, xl2.49 and xl2.51 are major determinants of the species preference for yohimbine and rauwolscine of the human versus mouse alpha(2A)-adrenoceptors. Residues at positions xl2.49 and xl2.51 determine the binding preference of RS-79948-197 for the human alpha(2A)-adrenoceptor. Thus, XL2 is involved in determining the species preferences of alpha(2A)-adrenoceptors of human and mouse for some antagonists.

PET amyloid ligand [11C]PIB uptake is increased in mild cognitive impairment

BACKGROUND

Patients with mild cognitive impairment (MCI) have increased risk to develop Alzheimer disease (AD). In AD increased brain amyloid burden has been demonstrated in vivo with PET using N-methyl-[(11)C]2-(4'-methylaminophenyl)-6-hydroxybenzothiazole ([(11)C]PIB) as a tracer.

OBJECTIVE

To investigate whether patients with amnestic MCI would show increased [(11)C]PIB uptake, indicating early AD process.

METHODS

We studied 13 patients with amnestic MCI and 14 control subjects with PET using [(11)C]PIB as tracer. Parametric images were computed by calculating the region-to-cerebellum ratio in each voxel over 60 to 90 minutes. Group differences in [(11)C]PIB uptake were analyzed with statistical parametric mapping (SPM) and automated region-of-interest (ROI) analysis.

RESULTS

The SPM analysis showed that patients with MCI had significantly higher [(11)C]PIB uptake vs control subjects in the frontal, parietal, and lateral temporal cortices as well as in the posterior cingulate showing the most prominent differences. These results were supported by the automated ROI analysis in which MCI patients showed in comparison with healthy control subjects increased [(11)C]PIB uptake in the frontal cortex (39% increase from the control mean, p < 0.01), the posterior cingulate (39%, p < 0.01), the parietal (31%, p < 0.01) and lateral temporal (28%, p < 0.001) cortices, putamen (17%, p < 0.05), and caudate (25%, p < 0.05). Individually, in the frontal cortex and posterior cingulate, 8 of 13 patients with MCI had [(11)C]PIB uptake values above 2 SD from the control mean. MCI subjects having at least one APOE epsilon4 allele tended to have higher [(11)C]PIB uptake than MCI subjects without APOE epsilon4.

CONCLUSIONS

At group level the elevated N-methyl-[(11)C]2-(4'-methylaminophenyl)-6-hydroxybenzothiazole ([(11)C]PIB) uptake in patients with mild cognitive impairment (MCI) resembled that seen in Alzheimer disease (AD). At the individual level, about half of the MCI patients had [(11)C]PIB uptake in the AD range, suggestive of early AD process.

Assessing the depth of dexmedetomidine-induced sedation with electroencephalogram (EEG)-based spectral entropy

BACKGROUND

Adequate sedation of critically ill patients improves the outcome of intensive care. Maintaining an optimal level of sedation in the intensive care unit (ICU) is difficult because of a lack of appropriate monitoring methods to guide drug dosing. Dexmedetomidine, a selective alpha(2)-adrenoceptor agonist, has recently been introduced for the sedation of ICU patients. This study investigated the utility of electroencephalogram (EEG)-based spectral entropy monitoring (with M-ENTROPY, GE Healthcare, Helsinki, Finland) for the assessment of dexmedetomidine-induced sedation.

METHODS

Eleven healthy, non-smoking men, aged 23.9 +/- 2.5 years (mean +/- standard deviation), were recruited. Spectral entropy was recorded before and during low (0.5 ng/ml) and high (5 ng/ml) plasma concentrations of dexmedetomidine. At the end of the infusion, subjects were awakened by verbal command and light shaking.

RESULTS

Spectral entropy decreased from 84 +/- 5 to 66 +/- 16 (P= 0.029) during low dexmedetomidine levels and from 84 +/- 5 to 20 +/- 12 (P < 0.001) during high dexmedetomidine levels. Transitions during loss and regaining of consciousness were analysed separately. Entropy decreased from 76 +/- 8 before to 43 +/- 10 (P < 0.001) after loss of consciousness, and increased from 14 +/- 4 to 63 +/- 13 (P < 0.001) on regaining of consciousness. These changes were consistent across all subjects. Prediction probability and sensitivity values indicated a high predictive performance of the method.

CONCLUSION

The depth of dexmedetomidine-induced sedation can be monitored with EEG-based spectral entropy. These results should be confirmed in a clinical setting.

Voxel-based analysis of PET amyloid ligand [11C]PIB uptake in Alzheimer disease

BACKGROUND

PET studies with N-methyl-[(11)C]2-(4':-methylaminophenyl)-6-hydroxybenzothiazole ([(11)C]PIB) have revealed an increased tracer uptake in several brain regions in Alzheimer disease (AD).

OBJECTIVE

To employ voxel-based analysis method to identify brain regions with significant increases in [(11)C]PIB uptake in AD vs healthy control subjects, indicative of increased amyloid accumulation in these regions.

METHODS

We studied 17 patients with AD and 11 control subjects with PET using [(11)C]PIB as tracer. Parametric images were computed by calculating a region-to-cerebellum ratio over 60 to 90 minutes in each voxel. Group differences in [(11)C]PIB uptake were analyzed with statistical parametric mapping (SPM) and automated region-of-interest (ROI) analysis.

RESULTS

SPM showed increased uptake (p < 0.001) in the frontal, parietal, and lateral temporal cortices as well as in the posterior cingulate and the striatum. No significant differences in uptake were found in the primary sensory and motor cortices, primary visual cortex, thalamus, and medial temporal lobe. These results were supported by automated ROI analysis, with most prominent increases in AD subjects in the frontal cortex ([(11)C]PIB uptake 163% of the control mean) and posterior cingulate (146%) followed by the parietal (146%) and temporal (145%) cortices and striatum (133%), as well as small increases in the occipital cortex (117%) and thalamus (115%).

CONCLUSIONS

Voxel-based analysis revealed widespread distribution of increased [(11)C]PIB uptake in Alzheimer disease (AD). These findings are in accordance with the distribution and phases of amyloid pathology in AD, previously documented in postmortem studies.

Pharmacokinetics of deramciclane and N-desmethylderamciclane after single and repeated oral doses in healthy volunteers

OBJECTIVE

To study the pharmacokinetics and accumulation of deramciclane and its metabolite N-desmethylderamciclane after 60 mg twice daily doses for 4 weeks.

METHODS

Sixteen healthy male subjects, age range of 20-29 years, participated in this randomized, double-blind, parallel-group, placebo-controlled study. Ten subjects first received a single 60 mg dose of deramciclane followed by 60 mg deramciclane b.i.d. between days 4 and 31. Six subjects received matching placebo in a similar manner. Pharmacokinetics of deramciclane and N-desmethylderamciclane were determined on days 1, 10, 17, 24 and 31. Plasma prolactin concentrations were measured before drug administration and 4 hours after on the same days. Safety was monitored using repeat laboratory determinations and ECG recordings.

RESULTS

The mean (SD) AUC(0-infinity) of deramciclane was 1,251 (385) ng x h/ml after the first dose. The AUC(tau) calculated for the dosing interval was significantly higher at week 1 (p = 0.048) than the AUC(0-infinity) after the first dose but thereafter there was no further accumulation of deramciclane. The mean accumulation indices at weeks 1, 2, 3 and 4 varied between 2.3 and 2.7 with no tendency to increase over time. The mean apparent elimination half-life of deramciclane was 24.9 (3.5) hours after the first dose and 29.3 (9.3) hours after 4-week repeated dosing; this difference was not statistically significant. The accumulation index of N-desmethylderamciclane increased from week 1 to week 2 but remained stable thereafter. The treatment was well tolerated. Plasma prolactin levels were not influenced by deramciclane administration.

CONCLUSIONS

Deramciclane administration, 60 mg twice daily for 4 weeks to healthy male volunteers, is well tolerated, and there is no evidence of continuous accumulation of the drug during maintenance treatment. Deramciclane at a dose of 60 mg b.i.d. does not antagonize dopamine receptors to a significant degree.

Regional distribution of alpha(2C)-adrenoceptors in brain and spinal cord of control mice and transgenic mice overexpressing the alpha(2C)-subtype: an autoradiographic study with [(3)H]RX821002 and [(3)H]rauwolscine

Behavioral studies on gene-manipulated mice have started to elucidate the neurobiological functions of the alpha(2C)-adrenoceptor (AR) subtype. In this study, we applied quantitative receptor autoradiography to investigate the potential anatomical correlates of the observed functional effects of altered alpha(2C)-AR expression. Labeling of brain and spinal cord sections with the subtype non-selective alpha(2)-AR radioligand [(3)H]RX821002 and the alpha(2C)-AR-preferring ligand [(3)H]rauwolscine revealed distinct binding-site distribution patterns. In control mice, [(3)H]rauwolscine binding was most abundant in the olfactory tubercle, accumbens and caudate putamen nuclei, and in the CA1 field of the hippocampus. A mouse strain with overexpression of alpha(2C)-AR regulated by a gene-specific promoter showed approximately two- to four-fold increased levels of [(3)H]rauwolscine binding in these regions. In addition, dramatic increases in [(3)H]rauwolscine binding were seen in the nerve layer of the olfactory bulb, the molecular layer of the cerebellum, and the ventricular system of alpha(2C)-AR-overexpressing mice, representing "ectopic" alpha(2C)-AR expression. Competition-binding experiments with several alpha(2)-AR ligands confirmed the alpha(2C)-AR identity of these sites. Our results provide quantitative evidence of the predominance of the alpha(2A)-AR subtype in most regions of the mouse CNS, but also disclose the wide distribution of alpha(2C)-AR in the normal mouse brain, although at relatively low density, except in the ventral and dorsal striatum and the hippocampal CA1 area. alpha(2C)-AR are thus present in brain regions involved in the processing of sensory information and in the control of motor and emotion-related activities such as the accumbens and caudate putamen nuclei, the olfactory tubercle, the lateral septum, the hippocampus, the amygdala, and the frontal and somatosensory cortices. The current results may help in specifying an anatomical framework for the functional roles of the alpha(2A)- and alpha(2C)-AR subtypes in the mouse CNS.

Behavioral and neurochemical characterization of alpha(2A)-adrenergic receptor knockout mice

Genetic manipulation of mice now provides new tools to evaluate the biological functions of the alpha(2)-adrenergic receptor (alpha(2)-AR) subtypes (alpha(2A), alpha(2B), and alpha(2C)). To investigate the role of the alpha(2A)-AR in the modulation of mouse primary behavioral characteristics and brain neurochemistry, mice with targeted inactivation of the gene for the alpha(2A)-AR were compared with wild-type C57BL/6 control animals. First, a comprehensive behavioral screen was employed to provide a detailed characterization of basic neurologic functions. Thereafter, the mice were analyzed in three models of anxiety, i.e. the elevated-plus maze test, the marble burying test and the open field test. The diurnal activity pattern of the mice was assessed in a 24-h locomotor activity test. Furthermore, receptor autoradiography of the brain was performed using the subtype-non-selective alpha(2)-AR antagonist radioligand [(3)H]RS-79948-197. Lack of the alpha(2A)-AR was associated with alterations in autonomic functions, including increased heart rate and piloerection. The mutant mice also exhibited impaired motor coordination skills, increased anxiety-like behavior and an abnormal diurnal activity pattern. In addition, neurochemical analysis of monoamine neurotransmitters revealed a considerable increase in brain norepinephrine turnover in mice lacking alpha(2A)-AR. Our results provide further support for the crucial role of the alpha(2A)-AR in modulating brain noradrenergic neurotransmission and many aspects of mouse behavior and physiology.

Development of a scintiplate assay for recombinant human alpha(2B)-adrenergic receptor

A high-throughput solid-phase platform for ligand-binding assays using microtiter plates (Scintiplates) has been developed using the scintillation proximity assay principle. The system has been developed using human alpha(2B)-adrenergic receptor (alpha(2B)-AR) expressed from Semliki Forest virus vectors in CHO cells. Alpha(2B)-AR bind natural (adrenaline and noradrenaline) and synthetic ligands with different affinities to mediate a variety of physiological and pharmacological responses. Antagonist radioligands were used for the binding experiments, and the values obtained for the binding constants with the Scintiplate system are in good agreement with those obtained by the traditional filter-binding assay system. The Scintiplate assay offers the advantages of a high-throughput format over the filter-binding assay and is amenable for screening many compounds rapidly for generation of leads.

G-protein beta3 subunit C825T polymorphism: no association with risk for hypertension and obesity

OBJECTIVE

Several recent studies have indicated that a C825T polymorphism in the gene encoding the G-protein beta3 subunit is a significant risk factor for hypertension and obesity. In this study, we tested whether this polymorphism is associated with hypertension and obesity in white men.

DESIGN

Population-based prospective cohort study.

METHODS

We followed a cohort of 903 men, aged 42-61 years at baseline, for an average time of 4.2 years. Genotyping was performed by polymerase chain reaction.

RESULTS

The genotype distribution was in Hardy-Weinberg equilibrium: 514 (57%) had the CC genotype, 49 (5%) had the TT genotype and 340 (38%) were heterozygous (T:C = 0.24:0.76). There was no statistically significant difference between the genotype groups in respect to baseline and end of follow-up risk for hypertension or obesity, systolic or diastolic blood pressure, or body mass index.

CONCLUSION

We conclude that the C825T polymorphism of the G-protein beta3 subunit gene does not notably contribute to the development of hypertension or obesity, and is not a significant determinant for blood pressure and body mass index in white men.

Spatial working memory improvement by an alpha2-adrenoceptor agonist dexmedetomidine is not mediated through alpha2C-adrenoceptor

1. Aged alpha2C-adrenoceptor knockout and wild type mice were used to investigate whether alpha2C-adrenoceptors are involved in mediating the beneficial effects of alpha2-adrenoceptor agonist, dexmedetomidine, on spatial working memory. 2. A win-stay task in the radial arm maze was used to dissociate the effects of dexmedetomidine on working vs. reference memory. In addition, the animals were tested in simple response habit learning in the T-maze. 3. Knockout mice made more working memory errors after the change of the baited arm in radial arm maze, but after training reached again as accurate level of performance as wild type controls. Dexmedetomidine 5 and 10 microg/kg alleviated the increase in spatial working memory errors after the change of the baited arm in knockout mice. Knockout and wild type mice performed equally well in T-maze, and dexmedetomidine had no effect on this simple response learning. 4. The present results indicate that alpha2-adrenoceptor agonists have a selective effect on spatial working memory not only in monkeys but also in mice. Further, this study confirms our earlier finding that the presence of alpha2C-adrenoceptors is not necessary for the spatial working memory enhancing effect of alpha2-adrenoceptor agonists.

Phenoxybenzamine binding reveals the helical orientation of the third transmembrane domain of adrenergic receptors

Phenoxybenzamine (PB), a classical alpha-adrenergic antagonist, binds irreversibly to the alpha-adrenergic receptors (ARs). Amino acid sequence alignments and the predicted helical arrangement of the seven transmembrane (TM) domains suggested an accessible cysteine residue in transmembrane 3 of the alpha(2)-ARs, in position C(3.36) (in subtypes A, B, and C corresponding to amino acid residue numbers 117/96/135, respectively), as a possible site for the PB interaction. Irreversible binding of PB to recombinant human alpha(2)-ARs (90 nm, 30 min) reduced the ligand binding capacity of alpha(2A)-, alpha(2B)-, and alpha(2C)-AR by 81, 96, and 77%. When the TM3 cysteine, Cys(117), of alpha(2A)-AR was mutated to valine (alpha(2A)-C117V), the receptor became resistant to PB (inactivation, 10%). The beta(2)-AR contains a valine in this position (V(3.36); position number 117) and a cysteine in the preceding position (Cys(116)) and was not inactivated by PB (10 microm, 30 min) (inactivation 26%). The helical orientation of TM3 was tested by exchanging the amino acids at positions 116 and 117 of the alpha(2A)-AR and beta(2)-AR. The alpha(2A)-F116C/C117V mutant was resistant to PB (inactivation, 7%), whereas beta(2)-V117C was irreversibly inactivated (inactivation, 93%), confirming that position 3.36 is exposed to receptor ligands, and position 3.35 is not exposed in the binding pocket.

Immunoaffinity purification and reconstitution of human alpha(2)-adrenergic receptor subtype C2 into phospholipid vesicles

Large quantities of correctly folded, pure alpha(2)-adrenergic receptor protein are needed for structural analysis. We report here the first efficient method to purify human alpha(2)-adrenergic receptor subtype C2 to homogeneity from recombinant yeast Saccharomyces cerevisiae by one-step purification using a monoclonal antibody column (specific for alpha(2)C2). We show that the adrenoceptor antagonist phentolamine stabilized the receptor during purification. We used a very effective chaotropic agent, NaSCN, to elute the receptor from the immunoaffinity column with an overall yield of 34% before reconstitution. Ligand binding of detergent-solubilized, immunoaffinity-purified receptors could not be demonstrated, but partial recovery of ligand binding activity was achieved when purified receptors were reconstituted into phospholipid vesicles. The reconstituted receptors still bound radioligand after storage on ice for 4 weeks. This purification procedure can be easily scaled-up and thus demonstrates the utility of a monoclonal antibody column and NaSCN elution to purify large quantities of G-protein-coupled receptors.

An insertion/deletion polymorphism in the alpha2B-adrenergic receptor gene is a novel genetic risk factor for acute coronary events

OBJECTIVES

Our aim was to study whether an insertion/deletion (I/D) polymorphism in the alpha2B-adrenoceptor gene is associated with the risk for cardiovascular diseases.

BACKGROUND

alpha2-adrenoceptors mediate contraction of vascular smooth muscle and induce coronary vasoconstriction in humans. The alpha2-adrenoceptor subtype B mediates vasoconstriction in mice. A variant of the human alpha2B-adrenoceptor gene that encodes a D of three residues in an intracellular acidic motif has been shown to confer decreased receptor desensitization. This receptor variant could, therefore, be involved in diseases associated with enhanced vasoconstriction.

METHODS

This study was part of a prospective population-based study investigating risk factors for cardiovascular diseases in a cohort of middle-aged men from eastern Finland. Nine hundred twelve men aged 46 to 64 years were followed for an average time of 4.5 years.

RESULTS

In this study population, 192 men (21%) had the D/D genotype; 256 (28%) had the I/I genotype, and 464 (51%) had a heterozygous genotype. In a Cox model adjusting for other coronary risk factors, men with the D/D genotype had 2.2 times (95% confidence interval: 1.1 to 4.4, p = 0.02) the risk to experience an acute coronary event (n = 15 for D/D, 10 for I/I and 12 for I/D) compared with men carrying either of the other two genotypes. The alpha2B-adrenoceptor genotype was not associated with hypertension in this study population.

CONCLUSIONS

The D/D genotype of the alpha2B-adrenoceptor is a novel genetic risk factor for acute coronary events, but not for hypertension.

Molecular mechanism for agonist-promoted alpha(2A)-adrenoceptor activation by norepinephrine and epinephrine

We present a mechanism for agonist-promoted alpha(2A)-adrenergic receptor (alpha(2A)-AR) activation based on structural, pharmacological, and theoretical evidence of the interactions between phenethylamine ligands and alpha(2A)-AR. In this study, we have: 1) isolated enantiomerically pure phenethylamines that differ both in their chirality about the beta-carbon, and in the presence/absence of one or more hydroxyl groups: the beta-OH and the catecholic meta- and para-OH groups; 2) used [(3)H]UK-14,304 [5-bromo-N-(4,5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine; agonist] and [(3)H]RX821002 [2-(2-methoxy-1,4-benzodioxan-2-yl)-2-imidazoline; antagonist] competition binding assays to determine binding affinities of these ligands to the high- and low-affinity forms of alpha(2A)-AR; 3) tested the ability of the ligands to promote receptor activation by measuring agonist-induced stimulation of [(35)S]GTPgammaS binding in isolated cell membranes; and 4) used automated docking methods and our alpha(2A)-AR model to predict the binding modes of the ligands inside the alpha(2A)-AR binding site. The ligand molecules are sequentially missing different functional groups, and we have correlated the structural features of the ligands and ligand-receptor interactions with experimental ligand binding and receptor activation data. Based on the analysis, we show that structural rearrangements in transmembrane helix (TM) 5 could take place upon binding and subsequent activation of alpha(2A)-AR by phenethylamine agonists. We suggest that the following residues are important in phenethylamine interactions with alpha(2A)-AR: Asp113 (D(3.32)), Val114 (V(3.33)), and Thr118 (T(3.37)) in TM3; Ser200 (S(5.42)), Cys201 (C(5.43)), and Ser204 (S(5.46)) in TM5; Phe391 (F(6.52)) and Tyr394 (Y(6.55)) in TM6; and Phe411 (F(7.38)) and Phe412 (F(7.39)) in TM7.

Evaluation of the α2C-adrenoceptor as a neuropsychiatric drug target

The functional characterization of the three distinct alpha2-adrenoceptor (Q2-AR) subtypes was for long hampered by the inavailability of subtype-selective pharmacological probes. Recent studies with gene-targeted mice have revealed that the alpha2A-AR has a major role in the mediation of many prominent effects of subtype non-selective alpha2-AR agonists, i.e. sedation, analgesia, hypothermia, sympatho-inhibition, and reduction of blood pressure. We have now employed several neuropsychopharmacological test models to investigate the effects mediated by the alpha2C-AR subtype and this receptor's potential as a CNS drug target. The studies employed two genetically engineered mouse strains, having either a targeted inactivation of the alpha2C-AR gene (alpha2C-KO) or over-expressing the alpha2C-AR (alpha2C-OE). Lack of alpha2C-AR expression was associated with increased amphetamine-induced locomotor activity, startle reactivity, aggression, and activity in the forced swimming test; prepulse inhibition of the startle reflex was attenuated. Opposite changes were observed in the alpha2C-OE mice. The results suggest that the alpha2C-AR subtype has a distinct inhibitory role in the processing of sensory information and in the control of motor and emotion-related activities in the CNS. It is therefore possible that alpha2C-AR-selective drugs may have therapeutic value in the treatment of various neuropsychiatric disorders.

Alpha2C-adrenoceptor overexpression disrupts execution of spatial and non-spatial search patterns

We investigated the role of alpha2C-adrenoceptors in the modulation of spatial and non-spatial navigation behaviour. Alpha2C-adrenoceptor overexpressing mice developed an ineffective thigmotaxic search pattern characterized by swimming close to the pool walls during both spatial and non-spatial water maze training. A subtype-non-selective alpha2-adrenoceptor antagonist, atipamezole (1000 microg/kg, s.c.), fully reversed this impairment in their search strategy. Withdrawal of atipamezole at the end of spatial training resulted in an immediate disruption of the search pattern in alpha2C-adrenoceptor overexpressing mice. The swimming pattern of alpha2C-adrenoceptor overexpressing mice during a five day free swimming period was normal, when no cognitive component was required. Diazepam (0.3 and 1.0 mg/kg, i.p.), neither improved the accuracy in finding the platform nor decreased thigmotaxis. These results suggest that alpha2C-adrenoceptors may modulate the execution of complex navigation patterns.

alpha(2C)-Adrenoceptors modulate the effect of methylphenidate on response rate and discrimination accuracy in an operant test

The present study investigated the role of alpha(2C)-adrenoceptors in the regulation of activity and discrimination accuracy in an operant chamber test. We trained food deprived control and alpha(2C)-adrenoceptor knockout mice to collect liquid food rewards in an operant chamber during the light (20 s) period. No food reward was delivered during the dark period (40 s). The alpha(2C)-adrenoceptor knockout mice tended to make fewer total responses and collect less rewards than their controls after saline treatment. However, only response accuracy of alpha(2C)-adrenoceptor knockout mice was significantly lower than that of the control mice. Methylphenidate, a drug blocking dopamine re-uptake and increasing dopamine release, dose-dependently decreased the number of total responses and collected food rewards in control mice but increased those measures in alpha(2C)-adrenoceptor knockout mice. In addition, the effect of methylphenidate on discrimination accuracy differed between knockout and control mice. Our results indicate that alpha(2C)-adrenoceptors may regulate dopamine-mediated functions.

Antenatal and early postnatal dexamethasone treatment decreases cortisol secretion in preterm infants

Glucocorticoids are used antenatally to accelerate the maturation of fetal respiratory and cardiovascular systems when a threat of preterm delivery exists. Postnatally, they are used to prevent and treat respiratory distress syndrome. This study investigates the effects of antenatal (ACT) and early postnatal corticosteroid treatment (PCT) on serum cortisol and plasma catecholamine and adenosine 3',5'-cyclic monophosphate (cAMP) concentrations in preterm neonates. The infants in the ACT group had a significantly lower cortisol concentration than the infants in the non-ACT group on the first day of life. After birth, the infants were further divided into non-PCT and PCT groups. PCT suppressed cortisol levels significantly after 2 days, and the cortisol levels were still lower 2 days after discontinuation of PCT. No effect of PCT on plasma cAMP or catecholamine concentrations was observed. The results indicate that both ACT and a short PCT can significantly suppress basal cortisol levels in preterm infants.

Regulation of alpha(2A)-adrenoceptor expression by chronic stress in neurons of the brain stem

Alpha(2)-Adrenoceptors are supposed to be important regulatory elements in responses to stress. Previous receptor binding studies in male tree shrews have shown that chronic psychosocial stress down-regulates binding sites for alpha(2)-adrenergic ligands in several brain stem nuclei. The aim of the present study was to quantify effects of chronic subordination stress on expression of the alpha(2)-adrenoceptor subtype A gene in identified neurons of the brain stem. We partially cloned the alpha(2A)-adrenoceptor cDNA of the tree shrew (1.22 kb) and localized receptor RNA expression in brain stem neurons by in situ hybridization using a 35S-labeled cRNA probe (1.06 kb). To identify neurons expressing receptor mRNA, brain sections were first immunocytochemically stained with antibodies against tyrosine hydroxylase, phenylethanolamine-N-methyltransferase, or glutamate, and then processed for in situ hybridization. Furthermore, expression of receptor-specific RNA was quantified in single neurons of animals which had been psychosocially stressed during 4 weeks and in unstressed controls. We found strong in situ hybridization in the noradrenergic neurons of the locus coeruleus, but only weak labeling of A2 neurons in the solitary tract nucleus and no labeling of A1 neurons in the caudal ventrolateral medulla. Adrenergic neurons in the solitary tract nucleus (group C2) did not express the alpha(2A)-adrenoceptor, and C1 neurons in the rostral ventrolateral medulla showed only a minor labeling by the in situ probe. In contrast, large glutamatergic neurons in the lateral reticular nucleus were strongly labeled by the probe. Chronic psychosocial stress reduced alpha(2A)-adrenoceptor RNA expression in locus coeruleus neurons (-24.0%), in solitary tract neurons (-31.0%), and in neurons of the lateral reticular nucleus (-18.8%). These findings show that stress not only decreases the expression of the alpha(2A)-adrenergic autoreceptor in the locus coeruleus but also of alpha(2A)-heteroreceptors in glutamatergic neurons.

Frequency and clinical outcome of potentially harmful drug metabolic interactions in patients hospitalized on internal and pulmonary medicine wards: focus on warfarin and cisapride

Drug metabolic interactions present potential risks in patient care, but their frequency and relative importance as a clinical problem remains unclear. To assess the frequency and clinical outcome of potentially harmful drug metabolic interactions in hospitalized patients, the authors performed a survey of the medication data of patients treated on internal and pulmonary medicine wards in a university hospital. The database was searched for concomitantly administered drug pairs that would, according to Hansten and Horn's drug interaction database, carry a high risk for a clinically harmful metabolic drug interaction. Coadministrations involving warfarin or cisapride were subjected to further analysis regarding clinical outcome. A total of 142 patients were exposed to 150 interactions with potentially harmful clinical outcome, resulting in a frequency of 0.9% (95% CI 0.7% to 1.0%). Inhibition of warfarin metabolism by metronidazole produced significant overanticoagulation as evidenced by elevated international normalized ratio values, whereas inducers (rifampicin and phenobarbital) of warfarin metabolism significantly reduced the efficacy of warfarin. One case of minor bleeding and one case of clavicular vein thrombosis were detected as possible consequences of disturbed anticoagulation. The coadministration of cisapride and erythromycin significantly prolonged the corrected QT (QTc) interval and was associated with clinical symptoms of cardiac arrhythmias. Coadministration of cisapride with fluconazole or miconazole was not associated with prolongation of the QTc interval or cardiac sequelae. Evaluations of patient materials are needed to assess the clinical relevance of metabolic drug interactions.

Wound healing in denervated rat groin skin flap

The purpose of the present study was to investigate the effect of denervation on dermal wound healing in rat groin skin flaps for 1-10 weeks. The structural differences between wounds in normal and in denervated skin were investigated histologically using Herovici's staining. Pro alpha1(I) collagen mRNA levels were studied using Northern hybridization. Denervation and reinnervation of the skin flaps was demonstrated with quantitative noradrenaline determination and immunohistochemically using neurofilament and S-100 antibodies. Denervation of the skin did not seem to have any apparent effects on wound healing as assessed by light microscopy. There were no significant differences in pro alpha1(I) collagen mRNA levels either. The thin muscle layer underlying the skin was the only element that clearly responded to the denervation.

Morphine-induced cardiovascular stimulation: the effects of two doses on healthy subjects

In humans, morphine induces hypotension, probably because of histamine liberation. Earlier animal studies have, however, suggested that morphine can induce immediate cardiovascular stimulation when given as a sole medication. The aim of this study was to evaluate the initial effects of morphine on circulation, oxygen consumption, and plasma histamine and catecholamine concentrations. Oxycodone was used as a reference drug. Eight healthy volunteers received, in a random, cross-over, double-blinded fashion: 0.07 mg/kg morphine (M1); 0.14 mg/kg morphine (M2); 0.14 mg/kg oxycodone (O); and placebo (P) as a 2-min IV injection for pain. Mean arterial blood pressure (MAP), heart rate (HR), and oxygen consumption (VO(2)) were recorded. Plasma histamine and catecholamine concentrations were determined. Both M1 and M2 elicited an initial, but transient, increase in MAP from 84 +/- 5 to 96 +/- 9 mm Hg (P < 0.05) and from 83 +/- 8 to 100 +/- 10 mm Hg (P < 0.05), respectively. A parallel increase in HR was also seen after M1 (from 62 +/- 12 to 70 +/- 10 bpm, P < 0.05) and M2 (from 67 +/- 9 to 78 +/- 8 bpm, P < 0.05). After M2, this was accompanied by a simultaneous increase in VO(2) from 295 +/- 39 mL/min to 322 +/- 61 mL/min (P < 0.05). After O, as well as P, no increase in MAP or HR was detected. Plasma histamine and catecholamine concentrations were not clearly affected by any of the treatments. We conclude that the immediate effect of morphine on the hemodynamics of healthy volunteers was stimulation, not hypotension. This effect was not seen in conjunction with oxycodone, a morphine-like mu-receptor agonist.

IMPLICATIONS

In this double-blinded, randomized study, we evaluated whether morphine could induce immediate cardiovascular stimulation, as seen previously in animal studies. In healthy volunteers, during a painful stimulus, morphine caused an initial, transient hemodynamic stimulation, accompanied by increased oxygen consumption, without detectable release of histamine or catecholamines into the plasma. Oxycodone caused only minor hemodynamic alterations.

Influence of hydroxychloroquine on the bioavailability of oral metoprolol

AIMS

Hydroxychloroquine (HCQ) is used widely in the treatment of chronic inflammatory diseases such as rheumatoid arthritis. Since there is great interindividual variability in the pharmacokinetics of HCQ and chloroquine is a potent inhibitor of CYP2D6-catalysed pathways in vitro, we wished to study the interaction of HCQ with CYP2D6-mediated metabolism of other drugs in vivo.

METHODS

Metoprolol and dextromethorphan (DM) were selected as probe drugs because they are well-studied and widely used test substrates of CYP2D6. In this randomized, double-blind crossover study, seven healthy volunteers with extensive metabolizer phenotype for CYP2D6 ingested either 400 mg hydroxychloroquine or placebo daily for 8 days after which single oral dose pharmacokinetics of metoprolol were investigated. Dextromethorphan metabolic ratio (DM-MR) was also determined at baseline and after the ingestion of HCQ or placebo.

RESULTS

Concomitant administration of HCQ increased the bioavailability of metoprolol, as indicated by significant increases in the area under the plasma concentration-time curve (65 +/- 4.6%) and maximal plasma concentrations (72 +/- 6.9%) of metoprolol. While the DM-MR values were not significantly changed, the phenotypic classification of one individual, who was heterozygous for a mutant CYP2D6 allele, was converted to a poor metabolizer by HCQ administration.

CONCLUSIONS

HCQ inhibits metoprolol metabolism most probably by inhibiting its biotransformation by CYP2D6. The inhibitory effect of HCQ on dextromethorphan metabolism was not apparent when DM-MR was used as an indicator, except in an individual with limited CYP2D6 capacity.

Ligand recognition of serine-cysteine amino acid exchanges in transmembrane domain 5 of alpha2-adrenergic receptors by UK 14,304

Ligand binding of UK 14,304 reveals notable species (i.e., human-rodent) and receptor-subtype differences of alpha2-adrenergic receptors (alpha2-ARs). To study the molecular basis of the selectivity of UK 14,304, we compared a series of conservative serine-cysteine exchange mutants at ligand-accessible positions in transmembrane domain 5 of the human and mouse alpha2A-ARs. UK 14,304 bound with approximately 200-fold higher affinity to the human alpha2A-AR wild-type receptor compared with the human alpha2A-ARSer201 mutant, but only an approximately fivefold difference was seen with the corresponding mouse alpha2A-AR variant. These effects of cysteine-serine exchanges only involved the agonist low-affinity forms of the receptors, as the affinity of [3H]UK 14,304 for the agonist high-affinity receptor populations was not influenced. The apparent affinities of a set of eight structurally diverse alpha2-AR ligands (six agonists and two antagonists) were not influenced significantly by the cysteine-serine exchanges (except for oxymetazoline and yohimbine, with up to nine- and eightfold differences in affinity, respectively). We conclude that position 201 (a) plays a primary role in determining observed subtype/species selectivity of UK 14,304 in competitive antagonist radioligand binding assays and (b) does not determine the subtype selectivity of chlorpromazine.

Overexpression of alpha2C-adrenoceptors impairs water maze navigation

We investigated the role of overexpression of alpha2C-adrenoceptors in water maze navigation in mice transgenically manipulated to have a threefold overexpression of the alpha2C-adrenoreceptors. Alpha2C-adrenoreceptors overexpressing mice swam more in the peripheral annulus of the pool and did not find the hidden escape platform as well as the wild type control mice. A subtype-nonselective alpha2-adrenoreceptor antagonist, atipamezole (ATI, 1000 microg/kg, s.c.), fully reversed the deficit in platform finding and search strategy in overexpressing mice. Noradrenaline depletion (-95%) induced by N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) did not impair platform finding of wild type or overexpressing mice. The DSP-4 lesion slightly increased swimming in the peripheral annulus in wild type mice, but not in overexpressing mice. The DSP-4 lesion produced a dissociable effect on the action of atipamezole to improve platform finding and search strategy in overexpressing mice: atipamezole did not alleviate the platform finding deficit in DSP-4 lesioned overexpressing mice, but normalized their abnormal search strategy. These results suggest that the abnormal search pattern and deficit in the accuracy of platform finding are mediated by constitutive activity of overexpressed alpha2C-adrenoreceptors.

Functional assessment of recombinant human alpha(2)-adrenoceptor subtypes with cytosensor microphysiometry

We applied the Cytosensor Microphysiometry system to study the three human alpha(2)-adrenoceptor subtypes, alpha(2A), alpha(2B) and alpha(2C), expressed in Chinese hamster ovary (CHO) cells, and assessed its potential in the quantitative monitoring of agonist activity. The natural full agonist, (-)-noradrenaline, was used to define agonist efficacy. The imidazole derivative dexmedetomidine was a potent full agonist of all three receptor subtypes. The imidazolines clonidine and UK 14,304 (5-bromo-N-(4, 5-dihydro-1H-imidazol-2-yl)-6-quinoxalinamine) appeared to be partial agonists at alpha(2B)-adrenoceptors (E(max) approximately 60% of (-)-noradrenaline) but full agonists at alpha(2A)- and alpha(2C)-adrenoceptors. The responses mediated by all three alpha(2)-adrenoceptor subtypes were partly inhibited by the sodium-hydrogen (Na(+)/H(+)) exchange inhibitor, MIA (5-(N-methyl-N-isobutyl)-amiloride). The agonist responses were totally abolished by pretreatment with pertussis toxin in cells with alpha(2A)- and alpha(2C)-adrenoceptors, and partly abolished in cells with alpha(2B)-adrenoceptors. The residual signal in alpha(2B)-cells was sensitive to the intracellular Ca(2+)chelator, BAPTA (1,2-bis(2-aminophenoxy)ethane-N,N,N,N-tetraacetic acid acetoxymethyl ester). Cholera toxin (which acts on G(s)-proteins) had no effect on the agonist responses. The results suggest that the extracellular acidification responses mediated by all three human alpha(2)-adrenoceptor subtypes are dependent on Na(+)/H(+)exchange and G(i/o) pathways, and that alpha(2B)-adrenoceptors are capable of coupling to another, G(i/o)-independent and Ca(2+)-dependent signaling pathway.

Pharmacokinetics and safety of deramciclane during multiple oral dosing

Deramciclane is a new putative non-benzodiazepine-type anxiolytic compound. It is a selective serotonin 5-HT(2A) and 5-HT(2C) receptor antagonist and has also inverse agonist properties. The aim of this study was to reveal the pharmacokinetics and tolerability of deramciclane during repeated oral dosing in healthy male volunteers.

SUBJECTS, MATERIAL AND METHODS

A randomized double-blind, placebo-controlled design was used. The study had three consecutive groups that received first a single oral dose of 10, 30 and 60 mg of deramciclane followed by twice a day administration for seven days. The total number of subjects was 28. The pharmacokinetic parameters were calculated for a single dose and after repeated administration. Tolerability was assessed by monitoring safety laboratory variables, electrocardiogram, heart rate, blood pressure and adverse events.

RESULTS

The steady-state was reached during the seven-day administration. The pharmacokinetics of deramciclane was dose-proportional at steady-state at each dose level. Deramciclane accumulated about three-fold during repeated administration. The relative bioavailability of deramciclane increased about 1.4-fold compared to that of a single dose at each dose level. The mean elimination half-life of deramciclane for 10, 30 and 60 mg doses prolonged from 24.3, 20.9 and 22.9 h after a single dose to 30.5, 25.6 and 28.7 h at steady-state, respectively. Only few adverse events were reported, all mild and transient in nature. The most frequently reported adverse drug reactions were tiredness and headache. There were no deramciclane-induced changes in the clinical chemistry or hematology variables, blood pressure, heart rate or in electrocardiogram.

CONCLUSIONS

In conclusion, the pharmacokinetics of deramciclane is linear over the dose range of 10 - 60 mg at steady-state. The slight non-linearity within the dose levels during repeated administration of seven days was regarded as clinically irrelevant. Deramciclane was safe and well tolerated up to doses of 60 mg b.i.d. for seven days.

Factors associated with post-operative myocardial ischaemia in elderly patients undergoing major non-cardiac surgery

Forty patients (> 65 years) undergoing hip arthroplasty or peripheral vascular surgery both associated with high risk for post-operative myocardial ischaemia were randomized to receive either spinal or general anaesthesia. Ambulatory ECG recording (Holter) until the third post-operative morning, a daily 12-lead ECG and serum creatine kinase and troponine concentraItions were obtained. The number of ischaemic episodes, total duration of ischaemia and ischaemic minutes per hour were noted for each patient peri-operatively. Sixteen of the patients (40%) had post-operative myocardial ischaemia. An intra-operative increase in the plasma concentration of norepinephrine but not epinephrine was detected in the patients who later developed post-operative myocardial ischaemia. The increase in plasma norepinIephrine concentrations correlated with the decrease in core temperature. The type of anaesthesia had no effect on the incidence of myocardial ischaemia during or after surgery. Our results suggests that intra-operatively decreased core temperature and the increase in plasma concentration of norepinephrine probably caused peripheral vasoconstriction leading to latent cardiac dysfunction. These events should be avoided in the patients at risk of post-operative cardiac ischaemia.