Meta-analysis of transcriptomic studies of cytokinin-treated rice roots defines a core set of cytokinin response genes.

Cytokinins regulate diverse aspects of plant growth and development, primarily through modulation of gene expression. The cytokinin-responsive transcriptome has been thoroughly described in dicots, especially Arabidopsis, but much less so in monocots. Here, we present a meta-analysis of five different transcriptomic analyses of rice (Oryza sativa) roots treated with cytokinin, including three previously unpublished experiments. We developed a treatment method in which hormone is added to the media of rice seedlings grown in sterile hydroponic culture under a continuous airflow, which resulted in minimal perturbation of the seedlings, thus greatly reducing changes in gene expression in the absence of exogenous hormone. We defined a core set of 205 upregulated and 86 downregulated genes that were differentially expressed in at least three of the transcriptomic datasets. This core set includes genes encoding the type-A response regulators (RRs) and cytokinin oxidases/dehydrogenases, which have been shown to be primary cytokinin response genes. GO analysis revealed that the upregulated genes were enriched for terms related to cytokinin/hormone signaling and metabolism, while the downregulated genes were significantly enriched for genes encoding transporters. Variations of type-B RR binding motifs were significantly enriched in the promoters of the upregulated genes, as were binding sites for other potential partner transcription factors. The promoters of the downregulated genes were generally enriched for distinct cis-acting motifs and did not include the type-B RR binding motif. This analysis provides insight into the molecular mechanisms underlying cytokinin action in a monocot and provides a useful foundation for future studies of this hormone in rice and other cereals.

Tree diversity regulates forest pest invasion.

Nonnative pests often cause cascading ecological impacts, leading to detrimental socioeconomic consequences; however, how plant diversity may influence insect and disease invasions remains unclear. High species diversity in host communities may promote pest invasions by providing more niches (i.e., facilitation), but it can also diminish invasion success because low host dominance may make it more difficult for pests to establish (i.e., dilution). Most studies to date have focused on small-scale, experimental, or individual pest/disease species, while large-scale empirical studies, especially in natural ecosystems, are extremely rare. Using subcontinental-level data, we examined the role of tree diversity on pest invasion across the conterminous United States and found that the tree-pest diversity relationships are hump-shaped. Pest diversity increases with tree diversity at low tree diversity (because of facilitation or amplification) and is reduced at higher tree diversity (as a result of dilution). Thus, tree diversity likely regulates forest pest invasion through both facilitation and dilution that operate simultaneously, but their relative strengths vary with overall diversity. Our findings suggest the role of native species diversity in regulating nonnative pest invasions.

Continued insights into virus clearance validation across continuous capture chromatography.

Multi-column capture chromatography (MCC) has gained increased attention lately due to the significant economic and process-related advantages it offers compared to traditional batch mode chromatography. However, for wide adoption of this technology in the clinical and commercial space, it requires scalable models for viral validation. In this study, additional viral validation studies were conducted under cGLP guidelines to assess retro-(X-MuLV) and parvo-virus (minute virus of mice) clearance across twin-column continuous capture chromatography (CaptureSMB) to supplement work previously performed. A surrogate model was validated using standard batch mode chromatography equipment based on flow path modifications to mimic the loading strategy employed in CaptureSMB. In addition, aged resin was used in this surrogate format to assess the impact of resin lifetime on viral clearance during continuous capture operation. The impact of column loading was also explored to shed light on the viral clearance mechanisms of protein A chromatography in overloading conditions. The proposed approach greatly simplifies MCC virus validation studies, and provides a robust strategy for regulatory filing of continuous biomanufacturing processes.

Perioperative Continuation of Buprenorphine at Low-Moderate Doses Was Associated with Lower Postoperative Pain Scores and Decreased Outpatient Opioid Dispensing Compared with Buprenorphine Discontinuation.

OBJECTIVE: An increasing number of individuals are prescribed buprenorphine as medication-assisted treatment for opioid use disorder. Our institution developed guidelines for perioperative buprenorphine continuation with an algorithm for dose reduction based upon the surgical procedure and patient's maintenance dose. The objective of this study was to compare the effects of buprenorphine continuation with those of discontinuation on postoperative pain scores and outpatient opioid dispensing. DESIGN: Retrospective observational study. SUBJECTS: Surgical patients on buprenorphine from March 2018 to October 2018. Patients on buprenorphine for chronic pain and those with minor procedures were excluded from analysis. METHODS: We compared postoperative outpatient opioid dispensing and postanesthesia care unit (PACU) pain scores in patients where buprenorphine was continued compared with held perioperatively, collecting single surgical subspecialty prescriber data on outpatient full mu-opioid agonist prescriptions dispensed, converted into mean morphine equivalents. Buprenorphine formulations were not included in our morphine milligram equivalents (MME) total. RESULTS: There were 55 patients total (38 cont. vs 17 held). There was no difference in postoperative buprenorphine treatment adherence (91% cont. vs 88% held, P = 0.324). The number of opioid prescriptions dispensed was significantly higher with buprenorphine discontinuation (53% cont. vs 82% held, P = 0.011), as was MME dispensed (mean of 229 cont. vs mean of 521 held, P = 0.033). PACU pain scores were higher with buprenorphine discontinuation (mean 2.9 cont. vs mean 7.6 held, P < 0.001). CONCLUSIONS: There was a significant reduction in opioid prescriptions filled, MME dispensed, and PACU pain scores in patients where buprenorphine was continued vs held perioperatively. We provide evidence to support that buprenorphine can be continued perioperatively and that continuation is associated with decreased postoperative pain and decreased outpatient opioid dispensing. These results contribute to the existing literature supporting the perioperative continuation of buprenorphine.

Conserved bases for the initial cyclase in gibberellin biosynthesis: from bacteria to plants.

All land plants contain at least one class II diterpene cyclase (DTC), which utilize an acid-base catalytic mechanism, for the requisite production of ent-copalyl diphosphate (ent-CPP) in gibberellin A (GA) phytohormone biosynthesis. These ent-CPP synthases (CPSs) are hypothesized to be derived from ancient bacterial origins and, in turn, to have given rise to the frequently observed additional DTCs utilized in more specialized plant metabolism. However, such gene duplication and neo-functionalization has occurred repeatedly, reducing the utility of phylogenetic analyses. Support for evolutionary scenarios can be found in more specific conservation of key enzymatic features. While DTCs generally utilize a DxDD motif as the catalytic acid, the identity of the catalytic base seems to vary depending, at least in part, on product outcome. The CPS from Arabidopsis thaliana has been found to utilize a histidine-asparagine dyad to ligate a water molecule that serves as the catalytic base, with alanine substitution leading to the production of 8ß-hydroxy-ent-CPP. Here this dyad and effect of Ala substitution is shown to be specifically conserved in plant CPSs involved in GA biosynthesis, providing insight into plant DTC evolution and assisting functional assignment. Even more strikingly, while GA biosynthesis arose independently in plant-associated bacteria and fungi, the catalytic base dyad also is specifically found in the relevant bacterial, but not fungal, CPSs. This suggests functional conservation of CPSs from bacteria to plants, presumably reflecting an early role for derived diterpenoids in both plant development and plant-microbe interactions, eventually leading to GA, and a speculative evolutionary scenario is presented.

Delta-9-tetrahydrocannabinol intoxication is associated with increased prefrontal activation as assessed with functional near-infrared spectroscopy: A report of a potential biomarker of intoxication.

The primary psychoactive compound in cannabis, Δ9-tetrahydrocannabinol (THC), binds to cannabinoid receptors (CB1) present in high concentrations in the prefrontal cortex (PFC). It is unknown whether the PFC hemodynamic response changes with THC intoxication. We conducted the first double-blind, placebo-controlled, cross-over study of the effect of THC intoxication on functional near infrared spectroscopy (fNIRS) measures of PFC activation. Fifty-four adult, regular (at least weekly) cannabis users received a single oral dose of synthetic THC (dronabinol; 5-50 mg, dose individually tailored to produce intoxication) and identical placebo on two visits at least one week apart. fNIRS recordings were obtained during a working memory task (N-Back) at three timepoints: before THC/placebo, at 100 min (when peak effects were expected), and at 200 min after THC/placebo administration. Functional data were collected using a continuous-wave NIRS device, with 8 sources and 7 detectors arrayed over the forehead, resulting in 20 channels covering PFC regions. Participants also completed frequent heart rate measures and subjective ratings of intoxication. Approximately half of participants reported significant intoxication. Intoxication ratings were not correlated with dose of THC. Increases in heart rate significantly correlated with intoxication ratings after THC dosing. Results indicated that 100 min after THC administration, oxygenated hemoglobin (HbO) response significantly increased from pre-dose HbO levels throughout the PFC in participants who reported significant intoxication. Changes in HbO response significantly correlated with self-reported intoxication at 100 min after THC administration. Among those who reported intoxication, HbO response decreased at 200 min after THC, when intoxication had largely resolved, compared to the peak THC time point. This study demonstrates that THC intoxication causes increased PFC activity, and fNIRS of the PFC can measure this effect. Increased neural activation in PFC represents a potential biomarker for cannabis intoxication.

Intraspecific Niche Models for Ponderosa Pine (Pinus ponderosa) Suggest Potential Variability in Population-Level Response to Climate Change.

Unique responses to climate change can occur across intraspecific levels, resulting in individualistic adaptation or movement patterns among populations within a given species. Thus, the need to model potential responses among genetically distinct populations within a species is increasingly recognized. However, predictive models of future distributions are regularly fit at the species level, often because intraspecific variation is unknown or is identified only within limited sample locations. In this study, we considered the role of intraspecific variation to shape the geographic distribution of ponderosa pine (Pinus ponderosa), an ecologically and economically important tree species in North America. Morphological and genetic variation across the distribution of ponderosa pine suggest the need to model intraspecific populations: the two varieties (var. ponderosa and var. scopulorum) and several haplotype groups within each variety have been shown to occupy unique climatic niches, suggesting populations have distinct evolutionary lineages adapted to different environmental conditions. We utilized a recently available, geographically widespread dataset of intraspecific variation (haplotypes) for ponderosa pine and a recently devised lineage distance modeling approach to derive additional, likely intraspecific occurrence locations. We confirmed the relative uniqueness of each haplotype-climate relationship using a niche-overlap analysis, and developed ecological niche models (ENMs) to project the distribution for two varieties and eight haplotypes under future climate forecasts. Future projections of haplotype niche distributions generally revealed greater potential range loss than predicted for the varieties. This difference may reflect intraspecific responses of distinct evolutionary lineages. However, directional trends are generally consistent across intraspecific levels, and include a loss of distributional area and an upward shift in elevation. Our results demonstrate the utility in modeling intraspecific response to changing climate and they inform management and conservation strategies, by identifying haplotypes and geographic areas that may be most at risk, or most secure, under projected climate change.

Catalytic Bases and Stereocontrol in Lamiaceae Class II Diterpene Cyclases.

Plants from the widespread Lamiaceae family produce many labdane-related diterpenoids, a number of which serve medicinal roles, and whose biosynthesis is initiated by class II diterpene cyclases (DTCs). These enzymes utilize a general acid-base catalyzed cyclo-isomerization reaction to produce various stereoisomers of the eponymous labdaenyl carbocation intermediate, which can then undergo rearrangement and/or the addition of water prior to terminating deprotonation. Identification of the pair of residues that cooperatively serve as the catalytic base in the DTCs that produce ent-copalyl diphosphate (CPP) required for gibberellin phytohormone biosynthesis in all vascular plants has led to insight into the addition of water as well as rearrangement. Lamiaceae plants generally contain an additional DTC that produces the enantiomeric normal CPP, as well as others that yield hydroxylated products derived from the addition of water. Here the catalytic base in these DTCs was investigated. Notably, changing two adjacent residues that seem to serve as the catalytic base in the normal CPP synthase from Salvia miltiorrhiza (SmCPS) to the residues found in the closely related perigrinol diphosphate synthase from Marrubium vulgare (MvPPS), which produces a partially rearranged and hydroxylated product derived from the distinct syn stereoisomer of labdaenyl+, altered the product outcome in an unexpected fashion. Specifically, the relevant SmCPS:H315N/T316V double mutant produces terpentedienyl diphosphate, which is derived from complete substituent rearrangement of syn rather than normal labdaenyl+. Accordingly, alteration of the residues that normally serve as the catalytic base surprisingly can impact stereocontrol.

Dominant forest tree mycorrhizal type mediates understory plant invasions.

Forest mycorrhizal type mediates nutrient dynamics, which in turn can influence forest community structure and processes. Using forest inventory data, we explored how dominant forest tree mycorrhizal type affects understory plant invasions with consideration of forest structure and soil properties. We found that arbuscular mycorrhizal (AM) dominant forests, which are characterised by thin forest floors and low soil C : N ratio, were invaded to a greater extent by non-native invasive species than ectomycorrhizal (ECM) dominant forests. Understory native species cover and richness had no strong associations with AM tree dominance. We also found no difference in the mycorrhizal type composition of understory invaders between AM and ECM dominant forests. Our results indicate that dominant forest tree mycorrhizal type is closely linked with understory invasions. The increased invader abundance in AM dominant forests can further facilitate nutrient cycling, leading to the alteration of ecosystem structure and functions.

The elimination of positive priming with increasing prime duration reflects a transition from perceptual fluency to disfluency rather than bias against primed words.

With immediate repetition priming of forced choice perceptual identification, short prime durations produce positive priming (i.e., priming the target leads to higher accuracy, while priming the foil leads to lower accuracy). Many theories explain positive priming following short duration primes as reflecting increased perceptual fluency for the primed target (i.e., decreased identification latency). However, most studies only examine either accuracy or response times, rather than considering the joint constraints of response times and accuracy to properly address the role of decision biases and response caution. This is a critical oversight because several theories propose that the transition to negative priming following a long duration prime reflects a decision strategy to compensate for the effect of increased perceptual fluency. In contrast, the nROUSE model of Huber and O'Reilly (2003) explains this transition as reflecting perceptual habituation, and thus a change to perceptual disfluency. We confirmed this prediction by applying a sequential sampling model (the diffusion race model) to accuracy and response time distributions from a new single item same-different version of the priming task. In this way, we measured strategic biases and perceptual fluency in each condition for each subject. The nROUSE model was only applied to accuracy from the original forced-choice version of the priming task. This application of nROUSE produced separate predictions for each subject regarding the degree of fluency and disfluency in each condition, and these predictions were confirmed by the drift rate parameters (i.e., fluency) from the response time model in contrast to the threshold parameters (i.e., bias).

Pinus ponderosa: A checkered past obscured four species.

PREMISE OF THE STUDY: Molecular genetic evidence can help delineate taxa in species complexes that lack diagnostic morphological characters. Pinus ponderosa (Pinaceae; subsection Ponderosae) is recognized as a problematic taxon: plastid phylogenies of exemplars were paraphyletic, and mitochondrial phylogeography suggested at least four subdivisions of P. ponderosa. These patterns have not been examined in the context of other Ponderosae species. We hypothesized that putative intraspecific subdivisions might each represent a separate taxon. METHODS: We genotyped six highly variable plastid simple sequence repeats in 1903 individuals from 88 populations of P. ponderosa and related Ponderosae (P. arizonica, P. engelmannii, and P. jeffreyi). We used multilocus haplotype networks and discriminant analysis of principal components to test clustering of individuals into genetically and geographically meaningful taxonomic units. KEY RESULTS: There are at least four distinct plastid clusters within P. ponderosa that roughly correspond to the geographic distribution of mitochondrial haplotypes. Some geographic regions have intermixed plastid lineages, and some mitochondrial and plastid boundaries do not coincide. Based on relative distances to other species of Ponderosae, these clusters diagnose four distinct taxa. CONCLUSIONS: Newly revealed geographic boundaries of four distinct taxa (P. benthamiana, P. brachyptera, P. scopulorum, and a narrowed concept of P. ponderosa) do not correspond completely with taxonomies. Further research is needed to understand their morphological and nuclear genetic makeup, but we suggest that resurrecting originally published species names would more appropriately reflect the taxonomy of this checkered classification than their current treatment as varieties of P. ponderosa.

Extreme promiscuity of a bacterial and a plant diterpene synthase enables combinatorial biosynthesis.

Diterpenes are widely distributed across many biological kingdoms, where they serve a diverse range of physiological functions, and some have significant industrial utility. Their biosynthesis involves class I diterpene synthases (DTSs), whose activity can be preceded by that of class II diterpene cyclases (DTCs). Here, a modular metabolic engineering system was used to examine the promiscuity of DTSs. Strikingly, both a bacterial and plant DTS were found to exhibit extreme promiscuity, reacting with all available precursors with orthogonal activity, producing an olefin or hydroxyl group, respectively. Such DTS promiscuity enables combinatorial biosynthesis, with remarkably high yields for these unoptimized non-native enzymatic combinations (up to 15mg/L). Indeed, it was possible to readily characterize the 13 unknown products. Notably, 16 of the observed diterpenes were previously inaccessible, and these results provide biosynthetic routes that are further expected to enable assembly of more extended pathways to produce additionally elaborated 'non-natural' diterpenoids.

Blocking Deprotonation with Retention of Aromaticity in a Plant ent-Copalyl Diphosphate Synthase Leads to Product Rearrangement.

Substitution of a histidine, comprising part of the catalytic base group in the ent-copalyl diphosphate synthases found in all seed plants for gibberellin phytohormone metabolism, by a larger aromatic residue leads to rearrangements. Through a series of 1,2-hydride and methyl shifts of the initially formed bicycle predominant formation of (-)-kolavenyl diphosphate is observed. Further mutational analysis and quantum chemical calculations provide mechanistic insight into the basis for this profound effect on product outcome.

1.55Å-resolution structure of ent-copalyl diphosphate synthase and exploration of general acid function by site-directed mutagenesis.

BACKGROUND: The diterpene cyclase ent-copalyl diphosphate synthase (CPS) catalyzes the first committed step in the biosynthesis of gibberellins. The previously reported 2.25Å resolution crystal structure of CPS complexed with (S)-15-aza-14,15-dihydrogeranylgeranyl thiolodiphosphate (1) established the αßγ domain architecture, but ambiguities regarding substrate analog binding remained. METHOD: Use of crystallization additives yielded CPS crystals diffracting to 1.55Å resolution. Additionally, active site residues that hydrogen bond with D379, either directly or through hydrogen bonded water molecules, were probed by mutagenesis. RESULTS: This work clarifies structure-function relationships that were ambiguous in the lower resolution structure. Well-defined positions for the diphosphate group and tertiary ammonium cation of 1, as well as extensive solvent structure, are observed. CONCLUSIONS: Two channels involving hydrogen bonded solvent and protein residues lead to the active site, forming hydrogen bonded "proton wires" that link general acid D379 with bulk solvent. These proton wires may facilitate proton transfer with the general acid during catalysis. Activity measurements made with mutant enzymes indicate that N425, which donates a hydrogen bond directly to D379, and T421, which hydrogen bonds with D379 through an intervening solvent molecule, help orient D379 for catalysis. Residues involved in hydrogen bonds with the proton wire, R340 and D503, are also important. Finally, conserved residue E211, which is located near the diphosphate group of 1, is proposed to be a ligand to Mg(2+) required for optimal catalytic activity. GENERAL SIGNIFICANCE: This work establishes structure-function relationships for class II terpenoid cyclases.

A unified approach for quantifying invasibility and degree of invasion.

Habitat invasibility is a central focus of invasion biology, with implications for basic ecological patterns and processes and for effective invasion management. "Invasibility" is, however, one of the most elusive metrics and misused terms in ecology. Empirical studies and meta-analyses of invasibility have produced inconsistent and even conflicting results. This lack of consistency, and subsequent difficulty in making broad cross-habitat comparisons, stem in part from (1) the indiscriminant use of a closely related, but fundamentally different concept, that of degree of invasion (DI) or level of invasion; and (2) the lack of common invasibility metrics, as illustrated by our review of all invasibility-related papers published in 2013. To facilitate both cross-habitat comparison and more robust ecological generalizations, we clarify the definitions of invasibility and DI, and for the first time propose a common metric for quantifying invasibility based on a habitat's resource availability as inferred from relative resident species richness and biomass. We demonstrate the feasibility of our metric using empirical data collected from 2475 plots from three forest ecosystems in the eastern United States. We also propose a similar metric for DI. Our unified, resource-based metrics are scaled from 0 to 1, facilitating cross-habitat comparisons. Our proposed metrics clearly distinguish invasibility and DI from each other, which will help to (1) advance invasion ecology by allowing more robust testing of generalizations and (2) facilitate more effective invasive species control and management.

Novel product chemistry from mechanistic analysis of ent-copalyl diphosphate synthases from plant hormone biosynthesis.

An active-site water molecule coordinated by conserved histidine and asparagine residues seems to serve as the catalytic base in all ent-copalyl diphosphate synthases (CPSs). When these residues are substituted by alanine, the mutant CPSs produce stereochemically novel ent-8-hydroxy-CPP. Given the requisite presence of CPSs in all land plants for gibberellin phytohormone biosynthesis, such plasticity presumably underlies the observed extensive diversification of the resulting labdane-related diterpenoids.

Impact of year-long cannabis use for medical symptoms on brain activation during cognitive processes.

Importance: Cannabis is increasingly being used to treat medical symptoms, but the effects of cannabis use on brain function in those using cannabis for these symptoms is not known. Objective: To test whether brain activation during working memory, reward, and inhibitory control tasks, areas of cognition impacted by cannabis, showed increases following one year of cannabis use for medical symptoms. Design: This observational cohort study took place from July 2017 to July 2020 and is reported on in 2024. Setting: Participants were from the greater Boston area. Participants: Participants were recruited as part of a clinical trial based on seeking medical cannabis cards for anxiety, depression, pain, or sleep disorders, and were between 18 and 65 years. Exclusion criteria were daily cannabis use and cannabis use disorder at baseline. Main Outcomes and Measures: Outcomes were whole brain functional activation during tasks involving working memory, reward and inhibitory control at baseline and after one year of cannabis use. Results: Imaging was collected in participants before and one year after obtaining medical cannabis cards; 57 at baseline (38 female [66.7%]; mean [SD] age, 38.0 [14.6] years) at baseline, and 54 at one-year (37 female [68.5%]; mean [SD] age, 38.7 [14.3] years). Imaging was also collected in 32 healthy control participants (22 female [68.8%]; mean [SD] age, 33.8 [11.8] years) at baseline. In all groups and at both time points, functional imaging revealed canonical activations of the probed cognitive processes. No statistically significant difference in brain activation between the two timepoints (baseline and one-year) in those with medical cannabis cards and no association of changes in cannabis use frequency with brain activation were found. Conclusions and Relevance: Findings suggest that adults do not show significant neural effects in the areas of cognition of working memory, reward, and inhibitory control after one year of cannabis use for medical symptoms. The results warrant further studies that probe effects of cannabis at higher doses, with greater frequency, in younger age groups, and with larger, more diverse cohorts. Trial Registration: NCT03224468, https://clinicaltrials.gov/.

Intention to quit or reduce e-cigarettes, cannabis, and their co-use among a school-based sample of adolescents.

INTRODUCTION: Little is known about the prevalence and predictors of adolescents' intention to quit or reduce use of e-cigarettes and/or cannabis. METHODS: Frequencies of intention to change (quit, reduce) e-cigarettes and/or cannabis use were examined among 23,915 surveyed middle and high school students with sole and co-use. Predictors of intention to change were identified via LASSO/multilevel logistic regression. RESULTS: Among those with sole e-cigarette use (n = 543), 40.9 % intended to quit and 24.1 % intended to reduce; non-daily e-cigarette use predicted intention to quit and reduce e-cigarettes (p's < 0.03). Among those with sole cannabis use (n = 546), 10.6 % intended to quit and 25.1 % intended to reduce; absence of cannabis cravings predicted intention to reduce cannabis use (p < 0.01). Among those with co-use (n = 816), 26.2 % intended to either quit or reduce (quit/reduce) both substances, 27.5 % intended to quit/reduce e-cigarettes only, and 6.9 % intended to quit/reduce cannabis only. No predictors emerged for intention to change e-cigarette use among those with co-use (p's > 0.09), but younger age, lack of poly-tobacco use, and lack of cannabis craving predicted intention to quit/reduce cannabis use (p's < 0.04). CONCLUSIONS: More than half of adolescents with past-month e-cigarette use, regardless of concurrent cannabis use, expressed interest in changing their use. However, only heaviness of e-cigarette use emerged as a predictor of intention to change suggesting. While fewer students expressed interest in changing their cannabis use, cannabis cravings and poly-tobacco use predicted intent to change. Overall, findings emphasize the need to tailor interventions towards adolescents engaging in more problematic substance use patterns.

Intoxication due to Δ9-tetrahydrocannabinol is characterized by disrupted prefrontal cortex activity.

Neural states of impairment from intoxicating substances, including cannabis, are poorly understood. Cannabinoid 1 receptors, the main target of Δ9-tetrahydrocannabinol (THC), the primary intoxicating cannabinoid in cannabis, are densely localized within prefrontal cortex; therefore, prefrontal brain regions are key locations to examine brain changes that characterize acute intoxication. We conducted a double-blind, randomized, cross-over study in adults, aged 18-55 years, who use cannabis regularly, to determine the effects of acute intoxication on prefrontal cortex resting-state measures, assessed with portable functional near-infrared spectroscopy. Participants received oral THC (10-80 mg, individually dosed to overcome tolerance and achieve acute intoxication) and identical placebo, randomized for order; 185 adults were randomized and 128 completed both study days and had usable data. THC was associated with expected increases in subjective intoxication ratings (ES = 35.30, p < 0.001) and heart rate (ES = 11.15, p = 0.001). THC was associated with decreased correlations and anticorrelations in static resting-state functional connectivity within the prefrontal cortex relative to placebo, with weakest correlations and anticorrelations among those who reported greater severity of intoxication (RSFC between medial PFC-ventromedial PFC and DEQ scores, r = 0.32, p < 0.001; RSFC between bilateral mPFC and DEQ scores, r = -0.28, p = 0.001). Relative to placebo, THC was associated with increased variability (or reduced stability) in dynamic resting-state functional connectivity of the prefrontal cortex at p = 0.001, consistent across a range of window sizes. Finally, using frequency power spectrum analyses, we observed that relative to placebo, THC was associated with widespread reduced spectral power within the prefrontal cortex across the 0.073-0.1 Hz frequency range at p < 0.039. These neural features suggest a disruptive influence of THC on the neural dynamics of the prefrontal cortex and may underlie cognitive impairing effects of THC that are detectable with portable imaging. This study is registered in Clinicaltrials.gov (NCT03655717).

Contingency management is associated with positive changes in attitudes and reductions in cannabis use even after discontinuation of incentives among non-treatment seeking youth.

BACKGROUND: It is important to identify interventions that reduce harm in youth not motivated to change their cannabis use. This study evaluated how short-duration contingency management (CM) impacts cannabis use attitudes and behavior after abstinence incentives are discontinued among non-treatment seeking youth. METHODS: Participants (N=220) were randomized to 4 weeks of abstinence-based CM (CB-Abst; n=126) or monitoring (CB-Mon; n=94). Participants completed self-report and provided biochemical measures of cannabis exposure at baseline, end-of-intervention, and 4-week follow-up. Changes in self-reported cannabis use frequency (days/week; times/week) and biochemically verified creatinine-adjusted 11-nor-9-carboxy-tetrahydrocannabinol concentrations (CN-THCCOOH) were analyzed between groups from baseline to follow-up. In CB-Abst, cannabis use goals at end-of-intervention were described and changes in cannabis use at follow-up were explored by goals and cannabis use disorder (CUD) diagnosis. RESULTS: There was a group by visit interaction on cannabis use (days: beta=0.93, p=0.005; times: beta=0.71, p<0.001; CN-THCCOOH: beta=0.26, p=0.004), with reductions at follow-up detected only in CB-Abst. Following 4 weeks of abstinence, 68.4% of CB-Abst participants wanted to reduce or abstain from cannabis use following completion of CM. Those in CB-Abst who set end-of-intervention reduction goals and were without CUD had greater decreases in cannabis use frequency at follow-up (Goals*time on days/week: beta=-2.27, p<0.001; CUD*time on times/week: beta=0.48, SE=0.24, t=2.01, p=0.048). CONCLUSIONS: Findings support the utility of brief incentivized abstinence for generating motivation to reduce cannabis use and behavior change even after incentives end. This study supports CM as a potentially viable harm reduction strategy for those not yet ready to quit.