-
Neuropharmacology Sep 2024Diets high in sucrose and fat are becoming more prevalent the world over, accompanied by a raised prevalence of cardiovascular diseases, cancers, diabetes, obesity, and...
Diets high in sucrose and fat are becoming more prevalent the world over, accompanied by a raised prevalence of cardiovascular diseases, cancers, diabetes, obesity, and metabolic syndrome. Clinical studies link unhealthy diets with the development of mental health disorders, particularly depression. Here, we investigate the effects of 12 days of sucrose consumption administered as 2 L of 25% sucrose solution daily for 12 days in Göttingen minipigs on the function of brain receptors involved in reward and motivation, regulating feeding, and pre- and post-synaptic mechanisms. Through quantitative autoradiography of cryostat sections containing limbic brain regions, we investigated the effects of sucrose restricted to a 1-h period each morning, on the specific binding of [H]raclopride on dopamine D2/3 receptors, [H]UCB-J at synaptic vesicle glycoprotein 2A (SV2A), [H]MPEPγ at metabotropic glutamate receptor subtype 5 (mGluR5) and [H]SR141716A at the cannabinoid receptor 1 (CB1). Compared to control diet animals, the sucrose group showed significantly lower [H]UCB-J and [H]MPEPγ binding in the prefrontal cortex. The sucrose-consuming minipigs showed higher hippocampal CB1 binding, but unaltered dopamine D2/3 binding compared to the control group. We found that the sucrose diet reduced the synaptic density marker while increasing CB1 binding in limbic brain structures, which may subserve maladaptive changes in appetite regulation and feeding. Further studies of the effects of diets and lifestyle habits on brain neuroreceptor and synaptic density markers are warranted.
Topics: Animals; Swine, Miniature; Swine; Sucrose; Male; Receptor, Metabotropic Glutamate 5; Receptors, Cannabinoid; Synapses; Receptor, Cannabinoid, CB1; Receptors, Dopamine D2; Brain; Female; Receptors, Dopamine D3
PubMed: 38810925
DOI: 10.1016/j.neuropharm.2024.110018 -
Journal of Pharmacological and... 2024Receptor occupancy is an indicator of antipsychotic efficacy and safety. It is desirable to simultaneously determine the occupancy of multiple brain receptors as an...
Development of simultaneous determination of dopamine 2, histamine 1, and muscarinic acetylcholine receptor occupancies by antipsychotics using liquid chromatography with tandem mass spectrometry.
Receptor occupancy is an indicator of antipsychotic efficacy and safety. It is desirable to simultaneously determine the occupancy of multiple brain receptors as an indicator of the efficacy and central side effects of antipsychotics because many of these drugs have binding affinities for various receptors, such as dopamine 2 (D), histamine 1 (H), and muscarinic acetylcholine (mACh) receptors. The purpose of this study was to develop a method for the simultaneous measurement of multiple receptor occupancies in the brain by the simultaneous quantification of unlabeled tracer levels using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Rats were pre-administered with a vehicle, displacer, or olanzapine, and mixed solutions of raclopride, doxepin, and 3-quinuclidinyl benzilate (3-QNB) were administered (3, 10, and 30 μg/kg). The brain tissue and plasma tracer concentrations were quantified 45 min later using LC-MS/MS, and the binding potential was calculated. The highest binding potential was observed at 3 μg/kg raclopride, 10 μg/kg doxepin, and 30 μg/kg 3-QNB. Tracer-specific binding at these optimal tracer doses in the cerebral cortex was markedly reduced by pre-administration of displacers. D, H and mACh receptor occupancy by olanzapine increased in a dose-dependent manner, reaching 70-95%, 19-43%, and 12-45%, respectively, at an olanzapine dose range of 3-10 mg/kg. These results suggest that simultaneous determination of in vivo D, H, and mACh receptor occupancy is possible using LC-MS/MS.
Topics: Animals; Tandem Mass Spectrometry; Rats; Male; Antipsychotic Agents; Chromatography, Liquid; Receptors, Dopamine D2; Rats, Sprague-Dawley; Receptors, Muscarinic; Receptors, Histamine H1; Olanzapine; Brain; Benzodiazepines; Raclopride; Doxepin; Quinuclidinyl Benzilate; Dose-Response Relationship, Drug
PubMed: 38797366
DOI: 10.1016/j.vascn.2024.107518 -
Cortex; a Journal Devoted To the Study... Jul 2024Losses in dopamine (DA) functioning may contribute to aging-related decline in cognition. Hippocampal DA is necessary for successful episodic memory formation....
Losses in dopamine (DA) functioning may contribute to aging-related decline in cognition. Hippocampal DA is necessary for successful episodic memory formation. Previously, we reported that higher DA D2 receptor (D2DR) availability in hippocampus is beneficial for episodic memory only in older carriers of more advantageous genotypes of well-established plasticity-related genetic variations, the brain-derived neurotrophic factor (BDNF, rs6265) and the kidney and brain expressed protein (KIBRA, rs17070145) polymorphisms. Extending our observations to the longitudinal level, the current data show that individuals with one or no beneficial BDNF and KIBRA genotype (n = 80) decline more in episodic memory across five years, without any contribution of losses in hippocampal D2DR availability to memory decline. Although carriers of two beneficial genotypes (n = 39) did not decline overall in episodic memory, losses of hippocampal D2DR availability were predictive of episodic-memory decline among these individuals. Our findings have implications for interventions targeting DA modulation to enhance episodic memory in aging, which may not benefit all older individuals.
Topics: Humans; Receptors, Dopamine D2; Memory, Episodic; Hippocampus; Brain-Derived Neurotrophic Factor; Male; Female; Aged; Genotype; Aging; Polymorphism, Single Nucleotide; Middle Aged; Memory Disorders; Longitudinal Studies; Polymorphism, Genetic; Neuropsychological Tests; Aged, 80 and over; Intracellular Signaling Peptides and Proteins
PubMed: 38749085
DOI: 10.1016/j.cortex.2024.01.014 -
Psychopharmacology Jun 2024Evidence on the effect of dopamine D1-like and D2-like receptor antagonists on licking microstructure and the forced swimming response led us to suggest that (i)... (Review)
Review
RATIONALE
Evidence on the effect of dopamine D1-like and D2-like receptor antagonists on licking microstructure and the forced swimming response led us to suggest that (i) dopamine on D1-like receptors plays a role in activating reward-directed responses and (ii) the level of response activation is reboosted based on a process of evaluation of response efficacy requiring dopamine on D2-like receptors. A main piece of evidence in support of this hypothesis is the observation that the dopamine D2-like receptor antagonist raclopride induces a within-session decrement of burst number occurring after the contact with the reward. The few published studies with a detailed analysis of the time-course of this measure were conducted in our laboratory.
OBJECTIVES
The aim of this review is to recapitulate and discuss the evidence in support of the analysis of the within-session burst number as a behavioural substrate for the study of the mechanisms governing ingestion, behavioural activation and the related evaluation processes, and its relevance in the analysis of drug effects on ingestion.
CONCLUSIONS
The evidence gathered so far suggests that the analysis of the within-session time-course of burst number provides an important behavioural substrate for the study of the mechanisms governing ingestion, behavioural activation and the related evaluation processes, and might provide decisive evidence in the analysis of the effects of drugs on ingestion. However, further evidence from independent sources is necessary to validate the use and the proposed interpretation of this measure.
Topics: Dopamine; Animals; Humans; Receptors, Dopamine D1; Receptors, Dopamine D2; Time Factors; Dopamine Antagonists; Reward; Eating; Drinking Behavior; Dopamine D2 Receptor Antagonists
PubMed: 38702473
DOI: 10.1007/s00213-024-06600-1 -
BMJ Open Apr 2024Bariatric surgery (BS) is the treatment of choice for refractory obesity. Although weight loss (WL) reduces the prevalence of obesity-related comorbidities, not all...
Portuguese observational cross-sectional clinical imaging study protocol to investigate central dopaminergic mechanisms of successful weight loss through bariatric surgery.
INTRODUCTION
Bariatric surgery (BS) is the treatment of choice for refractory obesity. Although weight loss (WL) reduces the prevalence of obesity-related comorbidities, not all patients maintain it. It has been suggested that central mechanisms involving dopamine receptors may play a role in successful WL. This protocol describes an observational cross-sectional study to test if the binding of central dopamine receptors is similar in individuals who responded successfully to BS and age- and gender-matched normal-weight healthy individuals (controls). As secondary goals, the protocol will investigate if this binding correlates with key parameters such as age, hormonal status, anthropometric metrics and neurobehavioural scores. Finally, as exploratory goals, we will include a cohort of individuals with obesity before and after BS to explore whether obesity and type of BS (sleeve gastrectomy and Roux-en-Y gastric bypass) yield distinct binding values and track central dopaminergic changes resulting from BS.
METHODS AND ANALYSIS
To address the major research question of this observational study, positron emission tomography (PET) with [C]raclopride will be used to map brain dopamine type 2 and 3 receptors (D2/3R) non-displaceable binding potential (BP) of individuals who have successfully responded to BS. Mean regional D2/3R BP values will be compared with control individuals by two one-sided test approaches. The sample size (23 per group) was estimated to demonstrate the equivalence between two independent group means. In addition, these binding values will be correlated with key parameters to address secondary goals. Finally, for exploratory analysis, these values will be compared within the same individuals (before and after BS) and between individuals with obesity and controls and types of BS.
ETHICS AND DISSEMINATION
The project and informed consent received ethical approval from the Faculty of Medicine and the Coimbra University Hospital ethics committees. Results will be disseminated in international peer-reviewed journals and conferences.
Topics: Humans; Obesity, Morbid; Cross-Sectional Studies; Portugal; Bariatric Surgery; Gastric Bypass; Obesity; Weight Loss; Positron-Emission Tomography; Receptors, Dopamine; Observational Studies as Topic
PubMed: 38569700
DOI: 10.1136/bmjopen-2023-080702 -
NeuroImage. Clinical 2024Aberrant dopaminergic function is linked with motor, psychotic, and affective symptoms, but studies have typically compared a single patient group with healthy controls.
PURPOSE
Aberrant dopaminergic function is linked with motor, psychotic, and affective symptoms, but studies have typically compared a single patient group with healthy controls.
METHODS
Here, we investigated the variation in striatal (caudate nucleus, nucleus accumbens, and putamen) and thalamic type 2 dopamine receptor (DR) availability using [C]raclopride positron emission tomography (PET) data from a large sample of 437 humans including healthy controls, and subjects with Parkinson's disease (PD), antipsychotic-naïve schizophrenia, severe violent behavior, pathological gambling, depression, and overweight. We analyzed regional group differences in DR availability. We also analyzed the interregional correlation in DR availability within each group.
RESULTS
Subjects with PD showed the clearest decline in DR availability. Overall, the groups showed high interregional correlation in DR availability, while this pattern was weaker in violent offenders. Subjects with schizophrenia, pathological gambling, depression, or overweight did not show clear changes in either the regional receptor availability or the interregional correlation.
CONCLUSION
We conclude that the dopaminergic changes in neuropsychiatric conditions might not only affect the overall receptor availability but also how coupled regions are across people. The region-specific receptor availability more profoundly links to the motor symptoms, while the between-region coupling might be disrupted in violence.
Topics: Humans; Overweight; Receptors, Dopamine D2; Tomography, X-Ray Computed; Positron-Emission Tomography; Corpus Striatum; Dopamine; Parkinson Disease
PubMed: 38395027
DOI: 10.1016/j.nicl.2024.103578 -
Neurobiology of Aging Apr 2024Dopamine decline is suggested to underlie aging-related cognitive decline, but longitudinal examinations of this link are currently missing. We analyzed 5-year...
Dopamine decline is suggested to underlie aging-related cognitive decline, but longitudinal examinations of this link are currently missing. We analyzed 5-year longitudinal data for a sample of healthy, older adults (baseline: n = 181, age: 64-68 years; 5-year follow-up: n = 129) who underwent positron emission tomography with C-raclopride to assess dopamine D2-like receptor (DRD2) availability, magnetic resonance imaging to evaluate structural brain measures, and cognitive tests. Health, lifestyle, and genetic data were also collected. A data-driven approach (k-means cluster analysis) identified groups that differed maximally in DRD2 decline rates in age-sensitive brain regions. One group (n = 47) had DRD2 decline exclusively in the caudate and no cognitive decline. A second group (n = 72) had more wide-ranged DRD2 decline in putamen and nucleus accumbens and also in extrastriatal regions. The latter group showed significant 5-year working memory decline that correlated with putamen DRD2 decline, along with higher dementia and cardiovascular risk and a faster biological pace of aging. Taken together, for individuals with more extensive DRD2 decline, dopamine decline is associated with memory decline in aging.
Topics: Humans; Aged; Dopamine; Aging; Brain; Positron-Emission Tomography; Raclopride; Memory Disorders
PubMed: 38359585
DOI: 10.1016/j.neurobiolaging.2024.02.001 -
Neuropsychopharmacology : Official... May 2024The rewarding effects of stimulant drugs such as methylphenidate (MP) depend crucially on how fast they raise dopamine in the brain. Yet how the rate of drug-induced... (Randomized Controlled Trial)
Randomized Controlled Trial
The rewarding effects of stimulant drugs such as methylphenidate (MP) depend crucially on how fast they raise dopamine in the brain. Yet how the rate of drug-induced dopamine increases impacts brain network communication remains unresolved. We manipulated route of MP administration to generate fast versus slow dopamine increases. We hypothesized that fast versus slow dopamine increases would result in a differential pattern of global brain connectivity (GBC) in association with regional levels of dopamine D1 receptors, which are critical for drug reward. Twenty healthy adults received MP intravenously (0.5 mg/kg; fast dopamine increases) and orally (60 mg; slow dopamine increases) during simultaneous [C]raclopride PET-fMRI scans (double-blind, placebo-controlled). We tested how GBC was temporally associated with slow and fast dopamine increases on a minute-to-minute basis. Connectivity patterns were strikingly different for slow versus fast dopamine increases, and whole-brain spatial patterns were negatively correlated with one another (rho = -0.54, p < 0.001). GBC showed "fast>slow" associations in dorsal prefrontal cortex, insula, posterior thalamus and brainstem, caudate and precuneus; and "slow>fast" associations in ventral striatum, orbitofrontal cortex, and frontopolar cortex (p < 0.05). "Fast>slow" GBC patterns showed significant spatial correspondence with D1 receptor availability (estimated via normative maps of [C]SCH23390 binding; rho = 0.22, p < 0.05). Further, hippocampal GBC to fast dopamine increases was significantly negatively correlated with self-reported 'high' ratings to intravenous MP across individuals (r = -0.68, p = 0.015). Different routes of MP administration produce divergent patterns of brain connectivity. Fast dopamine increases are uniquely associated with connectivity patterns that have relevance for the subjective experience of drug reward.
Topics: Humans; Male; Adult; Female; Brain; Positron-Emission Tomography; Magnetic Resonance Imaging; Dopamine; Methylphenidate; Double-Blind Method; Young Adult; Raclopride; Central Nervous System Stimulants; Receptors, Dopamine D1; Neural Pathways; Dopamine Antagonists; Brain Mapping
PubMed: 38326458
DOI: 10.1038/s41386-024-01803-8 -
Neuropharmacology Apr 2024Adenosine A-receptors (AR) and dopamine D-receptors (DR) are known to work together in a synergistic manner. Inhibiting ARs by genetic or pharmacological means can...
Adenosine A-receptors (AR) and dopamine D-receptors (DR) are known to work together in a synergistic manner. Inhibiting ARs by genetic or pharmacological means can relief symptoms and have neuroprotective effects in certain conditions. We applied PET imaging to evaluate the impact of the AR antagonist KW6002 on DR availability and neuroinflammation in an animal model of Parkinson's disease. Male Wistar rats with 6-hydroxydopamine-induced damage to the right striatum were given 3 mg/kg of KW6002 daily for 20 days. Motor function was assessed using the rotarod and cylinder tests, and neuroinflammation and dopamine receptor availability were measured using PET scans with the tracers [C]PBR28 and [C]raclopride, respectively. On day 7 and 22 following 6-OHDA injection, rats were sacrificed for postmortem analysis. PET scans revealed a peak in neuroinflammation on day 7. Chronic treatment with KW6002 significantly reduced [C]PBR28 uptake in the ipsilateral striatum [normalized to contralateral striatum] and [C]raclopride binding in both striata when compared to the vehicle group. These imaging findings were accompanied by an improvement in motor function. Postmortem analysis showed an 84% decrease in the number of Iba-1 cells in the ipsilateral striatum [normalized to contralateral striatum] of KW6002-treated rats compared to vehicle rats on day 22 (p = 0.007), corroborating the PET findings. Analysis of tyrosine hydroxylase levels showed less dopaminergic neuron loss in the ipsilateral striatum of KW6002-treated rats compared to controls on day 7. These findings suggest that KW6002 reduces inflammation and dopaminergic neuron loss, leading to less motor symptoms in this animal model of Parkinson's disease.
Topics: Rats; Male; Animals; Parkinson Disease; Dopamine; Receptor, Adenosine A2A; Neuroinflammatory Diseases; Adenosine; Raclopride; Rats, Wistar; Oxidopamine; Purines
PubMed: 38325770
DOI: 10.1016/j.neuropharm.2024.109862 -
The International Journal of... Feb 2024Rats emit 50-kHz ultrasonic vocalizations (USVs) in response to nonpharmacological and pharmacological stimuli, with addictive psychostimulants being the most effective...
Divergent Acute and Enduring Changes in 50-kHz Ultrasonic Vocalizations in Rats Repeatedly Treated With Amphetamine and Dopaminergic Antagonists: New Insights on the Role of Dopamine in Calling Behavior.
BACKGROUND
Rats emit 50-kHz ultrasonic vocalizations (USVs) in response to nonpharmacological and pharmacological stimuli, with addictive psychostimulants being the most effective drugs that elicit calling behavior in rats. Earlier investigations found that dopamine D1-like and D2-like receptors modulate the emission of 50-kHz USVs stimulated in rats by the acute administration of addictive psychostimulants. Conversely, information is lacking on how dopamine D1-like and D2-like receptors modulate calling behavior in rats that are repeatedly treated with addictive psychostimulants.
METHODS
We evaluated the emission of 50-kHz USVs in rats repeatedly treated (×5 on alternate days) with amphetamine (1 mg/kg, i.p.) either alone or together with (1) SCH 23390 (0.1-1 mg/kg, s.c.), a dopamine D1 receptor antagonist; (2) raclopride (0.3-1 mg/kg, s.c.), a selective dopamine D2 receptor antagonist; or (3) a combination of SCH 23390 and raclopride (0.1 + 0.3 mg/kg, s.c.). Calling behavior of rats was recorded following pharmacological treatment, as well as in response to the presentation of amphetamine-paired cues and to amphetamine challenge (both performed 7 days after treatment discontinuation).
RESULTS
Amphetamine-treated rats displayed a sensitized 50-kHz USV emission during repeated treatment, as well as marked calling behavior in response to amphetamine-paired cues and to amphetamine challenge. Antagonism of D1 or D2 receptors either significantly suppressed or attenuated the emission of 50-kHz USVs in amphetamine-treated rats, with a maximal effect after synergistic antagonism of both receptors.
CONCLUSIONS
These results shed further light on how dopamine transmission modulates the emission of 50-kHz USVs in rats treated with psychoactive drugs.
Topics: Rats; Animals; Amphetamine; Dopamine; Dopamine Antagonists; Raclopride; Ultrasonics; Vocalization, Animal; Central Nervous System Stimulants
PubMed: 38174899
DOI: 10.1093/ijnp/pyae001