Radioligand binding analysis of α₂ adrenoceptors with [¹¹C]yohimbine in brain in vivo:Extended Inhibition Plot correction for plasma protein binding

Abstract We describe a novel method of kinetic analysis of radioligand binding to neuroreceptors in brain in vivo, here applied to noradrenaline receptors in rat brain. The method uses positron emission tomography (PET) of [11C]yohimbine binding in brain to quantify the density and affinity of α 2 adrenoceptors under condition of changing radioligand binding to plasma proteins. We obtained dynamic PET recordings from brain of Spraque Dawley rats at baseline, followed by pharmacological challenge with unlabeled yohimbine (0.3 mg/kg). The challenge with unlabeled ligand failed to diminish radioligand accumulation in brain tissue, due to the blocking of radioligand binding to plasma proteins that elevated the free fractions of the radioligand in plasma. We devised a method that graphically resolved the masking of unlabeled ligand binding by the increase of radioligand free fractions in plasma. The Extended Inhibition Plot introduced here yielded an estimate of the volume of distribution of non-displaceable ligand in brain tissue that increased with the increase of the free fraction of the radioligand in plasma. The resulting binding potentials of the radioligand declined by 50–60% in the presence of unlabeled ligand. The kinetic unmasking of inhibited binding reflected in the increase of the reference volume of distribution yielded estimates of receptor saturation consistent with the binding of unlabeled ligand

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

Author Correction: Radioligand binding analysis of α 2 adrenoceptors with [11C]yohimbine in brain in vivo: Extended Inhibition Plot correction for plasma protein binding

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper

Decreased in vivo α2 adrenoceptor binding in the Flinders Sensitive Line rat model of depression

Depression is a debilitating heterogenous disorder and the underlying mechanisms remain elusive. Alterations in monoaminergic neurotransmission, including noradrenergic, have been implicated in the etiology of depression. Although depression is difficult to model in animals, the availability of animal models with face, predictive and construct validity permits more in-depth investigations resulting in a greater understanding of the disease. We investigated the role of noradrenaline (NA) and α2 adrenoceptors in vivo in a genetic model of depression, the Flinders Sensitive Line (FSL) rat. We determined baseline differences in NA receptor volume of distribution to α2 adrenoceptors in FSL, in comparison with two routinely used controls, Flinders Resistant Line (FRL) and Sprague–Dawley (SD) rats using positron emission tomography (PET) imaging and the carbon-11 labeled radioligand yohimbine. We demonstrate a 42–47% reduction in the binding of the tracer in the cortex, striatum, cerebellum, thalamus and pons of FSL rats compared to the two control groups. Our results suggest that the behavioral deficits expressed in the FSL depression model are associated with functional over-activity of the NA systemTh. Maigaards Eftf. Fru Lily Benthine Lunds Fond af 1.6.1978; Aarhus University Hospital Department of Nuclear Medicine and PET Cente

Quantification of [¹¹C]yohimbine binding to α₂ adrenoceptors in rat brain <i>in vivo</i>

We quantified the binding potentials (BP(ND)) of [(11)C]yohimbine binding in rat brain to alpha-2 adrenoceptors to evaluate [(11)C]yohimbine as an in vivo marker of noradrenergic neurotransmission and to examine its sensitivity to the level of noradrenaline. Dual [(11)C]yohimbine dynamic positron emission tomography (PET) recordings were applied to five Sprague Dawley rats at baseline, followed by acute amphetamine administration (2 mg/kg) to induce elevation of the endogenous level of noradrenaline. The volume of distribution (V(T)) of [(11)C]yohimbine was obtained using Logan plot with arterial plasma input. Because alpha-2 adrenoceptors are distributed throughout the brain, the estimation of the BP(ND) is complicated by the absence of an anatomic region of no displaceable binding. We used the Inhibition plot to acquire the reference volume, V(ND), from which we calculated the BP(ND). Acute pharmacological challenge with amphetamine induced a significant decline of [(11)C]yohimbine BP(ND) of ~38% in all volumes of interest. The BP(ND) was greatest in the thalamus and striatum, followed in descending order by, frontal cortex, pons, and cerebellum. The experimental data demonstrate that [(11)C]yohimbine binding is sensitive to a challenge known to increase the extracellular level of noradrenaline, which can benefit future PET investigations of pathologic conditions related to disrupted noradrenergic neurotransmission

Pubertal Effects on Executive Functioning Among Autistic and Non-Autistic Youth: A Cross Sectional Study

Investigating the role of puberty on executive function (EF) development is important for understanding how maturation and its related changes can impact neural systems underlying EF in autistic (AT) adolescents. Studies document chronological age-related differences in EF among AT youth, but the impact of puberty is understudied. We examined the role of cross-sectional pubertal status (Pubertal Development Scale adrenal and gonadal indices), autism status, and assigned sex at birth on parent-reported EF (Behavior Rating Inventory of Executive Function: inhibition, shift, working memory) in AT and non-autistic (NA) youth. We hypothesized AT youth, particularly females, would show more EF problems in late puberty relative to NA youth. AT males and females and NA females in late puberty had fewer shift problems relative to pre-pubertal youth, whereas NA males in late puberty had more shift problems relative to pre-pubertal NA males. There were no significant assigned sex or puberty differences in working memory for adrenal development and in any EF domain for gonadal development. Findings suggest adrenal puberty contributes to flexibility and may promote certain EF domains in AT youth. Longitudinal research using diverse measures of puberty and EF is needed to clarify findings

&alpha;-Synuclein Overexpression Increases Dopamine D2/3 Receptor Binding and Immune Activation in a Model of Early Parkinson&rsquo;s Disease

Progressive degeneration of dopaminergic neurons, immune activation, and &alpha;-synuclein pathology characterize Parkinson&rsquo;s disease (PD). We previously reported that unilateral intranigral injection of recombinant adeno-associated viral (rAAV) vectors encoding wild-type human &alpha;-synuclein produced a rat model of early PD with dopamine terminal dysfunction. Here we tested the hypothesis that decreases in dopamine result in increased postsynaptic dopamine D2/D3 receptor expression, neuroinflammation, and reduced synaptic vesicle glycoprotein 2A (SV2A) density. Rats were injected with rAAV encoding &alpha;-synuclein or green fluorescent protein and subjected to non-pharmacological motor tests, before euthanization at 12 weeks post-injection. We performed: (1) in situ hybridization of nigral tyrosine hydroxylase mRNA, (2) HPLC of striatal dopamine content, and (3) autoradiography with [3H]raclopride, [3H]DTBZ, [3H]GBR12935, [3H]PK11195, and [3H]UCB-J to measure binding at D2/3 receptors, vesicular monoamine transporter 2, dopamine transporters, mitochondrial translocator protein, and SV2A, respectively. rAAV-&alpha;-synuclein induced motor asymmetry and reduced tyrosine hydroxylase mRNA and dopamine content in ipsilateral brain regions. This was paralleled by elevated ipsilateral postsynaptic dopamine D2/3 receptor expression and immune activation, with no changes to synaptic SV2A density. In conclusion, &alpha;-synuclein overexpression results in dopaminergic degeneration that induced compensatory increases in D2/3 binding and immune activation, recapitulating many of the pathological characteristics of PD