Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 3 complete abstracts (631 words), 9 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
Organic nitrogenous bases. Many alkaloids of medical importance occur in the animal and vegetable kingdoms, and some have been synthesized. (Grant and Hackh's Chemical Dictionary, 5th ed)
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Alkaloid; Plant Alkaloids; Alkaloids, Plant; Plant Alkaloid; Alkaloid, Plant.
Where it fits in the MeSH classification
- Broader topics
- Heterocyclic Compounds
- Narrower topics
- 1-Deoxynojirimycin; Acridones; Amaryllidaceae Alkaloids; Anabasine; Arecoline; Benzophenanthridines; Benzylisoquinolines; Betalains; Camptothecin; Cinchona Alkaloids; Colchicine; Dihydro-beta-Erythroidine; Diterpene Alkaloids; Emetine
Research landscape
PubMed indexes 525,458 records tagged with the MeSH heading “Alkaloids” (counts retrieved 2026-10-31). 65,326 of them (12.4%) were published from 2020 onward, and the busiest period so far is through 1999 with 271,626 records.
Reviews account for 34,089 records (6.5%) and meta-analyses for 2,608. Randomized controlled trials number 25,505 (4.9%) as a share of all records on the topic.
Show the data
| Period | Records |
|---|---|
| through 1999 | 271,626 |
| 2000-2009 | 90,834 |
| 2010-2019 | 97,672 |
| 2020 onward | 65,326 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 34,089 | 6.5% |
| Meta-analyses | 2,608 | 0.5% |
| Randomized controlled trials | 25,505 | 4.9% |
Method: PubMed query "Alkaloids"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in drugs and chemicals
Studies of a chemical or drug can answer very different questions: what it is and how it behaves in cells and animals, how the body handles it, and whether it changes outcomes in people. Laboratory and animal findings often do not carry over to patients, and observational studies of exposures are confounded by who uses a substance and why. Nothing on this page is a recommendation to use, avoid, start or stop any substance or medicine; talk to a qualified clinician or pharmacist about your own situation. Check the dose, the species, the comparison group and whether a patient-relevant outcome was measured.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| Thalamo-accumbal circuit adaptations following extended oxycodone abstinence | 2026 | Research article Design not recorded in structured metadata | 5 | cc by PMID 42550587 · DOI · PMC13436959 |
| Psilocybin-assisted therapy for treatment-resistant major depressive disorder in a public healthcare setting: a randomized controlled trial | 2026 | Randomized controlled trial Design not recorded in structured metadata | 2 | cc by PMID 42562964 · DOI · PMC13577891 |
| Psychedelics align brain activity with context | 2026 | Research article Design not recorded in structured metadata | 2 | cc by PMID 42618786 · DOI · PMC13518247 |
Thalamo-accumbal circuit adaptations following extended oxycodone abstinence [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Opioid use disorder is characterized by compulsive drug seeking and heightened relapse vulnerability following abstinence, a phenomenon known as incubation of craving.
- Closing excerpt
- The dissociation between comparable circuit-level plasticity and sex-specific relapse vulnerability suggests that PVT-NAcSh strengthening represents a shared neuroadaptation to oxycodone abstinence, while mechanisms driving heightened relapse in females likely involve additional circuit elements that remain to be identified.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (195 words)
Opioid use disorder is characterized by compulsive drug seeking and heightened relapse vulnerability following abstinence, a phenomenon known as incubation of craving. Although preclinical data suggest similar behavioral expression of opioid use between sexes, conclusive evidence on sex differences in craving and relapse across abstinence periods remains lacking. Here, we investigated the effects of abstinence from oxycodone self-administration on neurotransmission in the paraventricular thalamus (PVT) to nucleus accumbens shell (NAcSh) pathway in male and female rats. Using optogenetics and ex vivo electrophysiology, we assessed synaptic strength, glutamate release probability, and intrinsic excitability of NAcSh medium spiny neurons (MSNs) following 1 (acute) or 14 (prolonged) days of forced abstinence. No sex differences were observed in oxycodone self-administration or somatic withdrawal. However, females exhibited greater cue-induced relapse after prolonged but not acute abstinence. Prolonged abstinence produced comparable increases in PVT-NAcSh synaptic strength and presynaptic glutamate release probability in both sexes, while inhibitory transmission and MSN excitability were largely unaltered. The dissociation between comparable circuit-level plasticity and sex-specific relapse vulnerability suggests that PVT-NAcSh strengthening represents a shared neuroadaptation to oxycodone abstinence, while mechanisms driving heightened relapse in females likely involve additional circuit elements that remain to be identified.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42550587 · DOI · PMC13436959
Psilocybin-assisted therapy for treatment-resistant major depressive disorder in a public healthcare setting: a randomized controlled trial [2]
Abstract reading summary — source excerpts
- Opening excerpt
- Psilocybin-assisted therapy may be a promising new treatment for treatment-resistant depression.
- Closing excerpt
- : 2018-003573-97 .
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (208 words)
Psilocybin-assisted therapy may be a promising new treatment for treatment-resistant depression. We examined the feasibility of administering a single 25-mg dose of psilocybin or placebo with psychological support in a randomized controlled trial design with 6 weeks of follow-up. A two-arm, double-blind, randomized, placebo-controlled feasibility trial was conducted at one National Health Service (NHS) site in England. Eligible participants met Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for major depressive disorder and had an inadequate response to ≥2 antidepressant treatments or ≥1 antidepressant plus ≥1 psychotherapy. Participants received 25-mg psilocybin or placebo with preparation, dosing support and integration. Primary outcomes were recruitment, retention and estimation of the Montgomery-Åsberg Depression Rating Scale (MADRS) variance. A multilevel regression analysis with an intention-to-treat population was used. Sixty participants were randomized (1:1), balanced by age, sex and prior psilocybin exposure, and 59 of 60 participants completed the MADRS at all follow-up visits. The adjusted between-group difference at week 3 on the MADRS was -10.41 (95% confidence interval: -14.86 to -5.95; Cohen's d = -1.70), favoring psilocybin, which was sustained at week 6. In total, 123 and 164 nonserious adverse events occurred in the placebo and psilocybin arms, respectively. Findings support a future confirmatory trial. EudraCT no.: 2018-003573-97 .
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42562964 · DOI · PMC13577891
Psychedelics align brain activity with context [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Psychedelics can profoundly alter consciousness by reorganizing brain connectivity1,2, producing acute experiences that shape lasting psychological change3,4.
- Closing excerpt
- Our findings recast apparent disorder as latent organization aligned with context, linking neurobiology to subjective experience and behavioural change.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (228 words)
Psychedelics can profoundly alter consciousness by reorganizing brain connectivity1,2, producing acute experiences that shape lasting psychological change3,4. Psychedelic dynamics are commonly described as desynchronized or entropically disordered5,6, yet the brain organization underlying self-dissolving and boundary-dissolving experiences that participants often report7, and how context shapes that organization8, remain unresolved. To address this, we acquired the largest single-site psychedelic neuroimaging dataset to date. Sixty-two adults underwent functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) during rest and naturalistic stimuli (meditation, music and movie), before and on the day of psilocybin administration (fMRI ~ 80 min post-dose; EEG ~ 150 min post-dose). Half ranked the experience among the most meaningful of their lives7. Here, using machine learning to represent the brain dynamics of each individual as low-dimensional trajectories, we show that psilocybin reorganizes brain activity into structured, context-sensitive patterns that co-vary with the quality of subjective experience, revealing a latent order missed by time-averaged measures. Networks that ordinarily segregate internal and external processing integrated, producing cohesive context-aligned trajectories in participants reporting the felt experience of being continuous with, rather than separate from, the environment, a state we refer to as embeddedness. The strength of this context alignment scaled with both the depth of self-dissolving and boundary-dissolving experience and the next-day mindset change. Our findings recast apparent disorder as latent organization aligned with context, linking neurobiology to subjective experience and behavioural change.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42618786 · DOI · PMC13518247
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Pharmacotherapy for Alcohol Use Disorder: A Systematic Review and Meta-Analysis [4]
- Research article Efficacy and Safety of 8 Atropine Concentrations for Myopia Control in Children: A Network Meta-Analysis [5]
- Research article The experimental effects of psilocybin on symptoms of anxiety and depression: A meta-analysis [6]
- Research article Buprenorphine versus methadone for the treatment of opioid dependence: a systematic review and meta-analysis of randomised and observational studies [7]
- Research article The effect of caffeine on subsequent sleep: A systematic review and meta-analysis [8]
- Research article Cholinesterase inhibitors for vascular dementia and other vascular cognitive impairments: a network meta-analysis [9]
References
- Alonso Caraballo Y, Li Y, Constantino NJ, Neal MA, Driscoll GS, Manasian Y, et al.. Thalamo-accumbal circuit adaptations following extended oxycodone abstinence. . 2026. PMID 42550587 · DOI · PMC13436959
- Rucker JJ, Mantingh T, Kerr-Gaffney J, Bird C, Chu P, Modlin NL, et al.. Psilocybin-assisted therapy for treatment-resistant major depressive disorder in a public healthcare setting: a randomized controlled trial. . 2026. PMID 42562964 · DOI · PMC13577891
- Stoliker D, Novelli L, Khajehnejad M, Biabani M, Greaves MD, Barta T, et al.. Psychedelics align brain activity with context. . 2026. PMID 42618786 · DOI · PMC13518247
- McPheeters M, O'Connor EA, Riley S, Kennedy SM, Voisin C, Kuznacic K, et al.. Pharmacotherapy for Alcohol Use Disorder: A Systematic Review and Meta-Analysis. JAMA. 2023. PMID 37934220 · DOI · PMC10630900
- Ha A, Kim SJ, Shim SR, Kim YK, Jung JH. Efficacy and Safety of 8 Atropine Concentrations for Myopia Control in Children: A Network Meta-Analysis. Ophthalmology. 2022. PMID 34688698 · DOI
- Goldberg SB, Pace BT, Nicholas CR, Raison CL, Hutson PR. The experimental effects of psilocybin on symptoms of anxiety and depression: A meta-analysis. Psychiatry Res. 2020. PMID 31931272 · DOI
- Degenhardt L, Clark B, Macpherson G, Leppan O, Nielsen S, Zahra E, et al.. Buprenorphine versus methadone for the treatment of opioid dependence: a systematic review and meta-analysis of randomised and observational studies. Lancet Psychiatry. 2023. PMID 37167985 · DOI
- Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, et al.. The effect of caffeine on subsequent sleep: A systematic review and meta-analysis. Sleep Med Rev. 2023. PMID 36870101 · DOI
- Battle CE, Abdul-Rahim AH, Shenkin SD, Hewitt J, Quinn TJ. Cholinesterase inhibitors for vascular dementia and other vascular cognitive impairments: a network meta-analysis. Cochrane Database Syst Rev. 2021. PMID 33704781 · DOI · PMC8407366
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.