Ameliorative effects of alkaloid extract from Mitragyna speciosa (Korth.) Havil. Leaves on methamphetamine conditioned place preference in mice

Local field potential (LFP) power and phase-amplitude coupling (PAC) changes in the striatum and motor cortex reflect neural mechanisms associated with bradykinesia and rigidity during D2R suppression in an animal model

Impairments in motor control are the primary feature of Parkinson's disease, which is caused by dopaminergic imbalance in the basal ganglia. Identification of neural biomarkers of dopamine D2 receptor (D2R) suppression would be useful for monitoring the progress of neuropathologies and effects of treatment. Male Swiss albino ICR mice were deeply anesthetized, and electrodes were implanted in the striatum and motor cortex to record local field potential (LFP). Haloperidol (HAL), a D2R antagonist, was administered to induce decreased D2R activity. Following HAL treatment, the mice showed significantly decreased movement velocity in open field test, increased latency to descend in a bar test, and decreased latency to fall in a rotarod test. LFP signals during HAL-induced immobility (open field test) and catalepsy (bar test) were analyzed. Striatal low-gamma (30.3-44.9 Hz) power decreased during immobility periods, but during catalepsy, delta power (1-4 Hz) increased, beta1(13.6-18 Hz) and low-gamma powers decreased, and high-gamma (60.5-95.7 Hz) power increased. Striatal delta-high-gamma phase-amplitude coupling (PAC) was significantly increased during catalepsy but not immobility. In the motor cortex, during HAL-induced immobility, beta1 power significantly increased and low-gamma power decreased, but during HAL-induced catalepsy, low-gamma and beta1 powers decreased and high-gamma power increased. Delta-high-gamma PAC in the motor cortex significantly increased during catalepsy but not during immobility. Altogether, the present study demonstrated changes in delta, beta1 and gamma powers and delta-high-gamma PAC in the striatum and motor cortex in association with D2R suppression. In particular, delta power in the striatum and delta-high-gamma PAC in the striatum and motor cortex appear to represent biomarkers of neural mechanisms associated with bradykinesia and rigidity.

Clinical Implications of Kratom (Mitragyna speciosa) Use: a Literature Review

Purpose of Review

This work aims to provide an up-to-date review of the preclinical and clinical scientific literature on the therapeutic value of kratom to better understand the underlying mechanisms related to its use and inform future therapeutic applications.

Recent Findings

A growing number of studies, mainly of cross-sectional nature, describe the widespread use of kratom by individuals to self-treat pain, psychiatric symptoms, and substance use disorders (SUD) outside a controlled clinical setting. Preclinical evidence suggests kratom is effective as an analgesic agent and might decrease the self-administration of other drugs. A randomized controlled trial has further supported kratom's therapeutic value as an analgesic. Investigations in nonclinical samples of long-term kratom users also indicate its therapeutic benefit in managing SUD symptoms (e.g., craving) and long-term or acute symptoms (e.g., withdrawal) for alcohol, opioids, and other illicit drugs. However, episodes of kratom-related intoxications have also been reported, often due to the adulteration and the contamination of kratom products mainly sold online or mixed toxicities when consumed outside clinical and traditional settings.

Summary

Evidence on the clinical implications of kratom use is still limited and uncertain, with kratom research constantly evolving. Therefore, further randomized trials are needed.

Seasonal and Geographic Variation in Alkaloid Content of Kratom (Mitragyna speciosa (Korth.) Havil.) from Thailand

The objective of this study was to obtain data on the distribution of alkaloids in kratom plants grown in Thailand. Two collections were performed, covering the southern, central, and northern regions of Thailand and different seasons. The contents of alkaloids, including mitragynine (MG), paynantheine (PAY), and speciogynine (SG), were determined using the validated HPLC method. The 134 samples in the first collection were collected from Nam Phu subdistrict, Ban Na San, Surat Thani, Thailand, during June and October 2019 and January 2020. The maximum mitragynine content was 4.94% w/w in June (late summer), and the minimum content was 0.74% w/w in October (rainy season). To expand the study area after kratom decriminalization, 611 samples were collected in June-August 2021, October-December 2021, and January-April 2022. The accumulation of MG ranged from 0.35 to 3.46% w/w, 0.31 to 2.54% w/w, and 0.48 to 2.81% w/w, respectively. The meteorological data supported the climate's effect on alkaloid production. Soil analysis revealed the importance of Ca and Mg in promoting alkaloid production. Geographical locations played a role in the variation of MG in kratom leaves, but did not affect the color of leaf veins. In conclusion, the present study suggested that the alkaloid content in kratom diverges based on seasonal and geographical origin.

ANet: Autoencoder-Based Local Field Potential Feature Extractor for Evaluating an Antidepressant Effect in Mice After Administering Kratom Leaf Extracts

Kratom (KT) typically exerts antidepressant (AD) effects. However, evaluating which form of KT extracts possesses AD properties similar to the standard AD fluoxetine (flu) remained challenging. Here, we adopted an autoencoder (AE)-based anomaly detector called ANet to measure the similarity of mice's local field potential (LFP) features that responded to KT leave extracts and AD flu. The features that responded to KT syrup had the highest similarity to those that responded to the AD flu at 87.11 ± 0.25%. This finding presents the higher feasibility of using KT syrup as an alternative substance for depressant therapy than KT alkaloids and KT aqueous, which are the other candidates in this study. Apart from the similarity measurement, we utilized ANet as a multi-task AE and evaluated the performance in discriminating multi-class LFP responses corresponding to the effect of different KT extracts and AD flu simultaneously. Furthermore, we visualized learned latent features among LFP responses qualitatively and quantitatively as t-SNE projection and maximum mean discrepancy distance, respectively. The classification results reported the accuracy and F1-score of 90.11 ± 0.11% and 90.08 ± 0.00%. In summary, the outcomes of this research might help therapeutic design devices for an alternative substance profile evaluation, such as Kratom-based form, in real-world applications.

A 1:1 ratio of cannabidiol: tetrahydrocannabinol attenuates methamphetamine conditioned place preference in mice: A prospective study of antidopaminergic mechanism

A 1:1 ratio of cannabidiol to tetrahydrocannabinol (CT) was suggested to be safer for therapeutic purposes in many illnesses. However, CT effects on methamphetamine (METH) conditioned place preference (CPP) remained largely unexplored. This study aimed to examine the effects of CT on METH CPP mice evaluated by animal behaviors accompanied by local field potential (LFP) signals analysis. Male ICR mice were implanted with the LFP electrode in the ventral tegmental area (VTA) and the nucleus accumbens (NAc). Animals were next subjected to induce METH CPP by peritoneal injection with 1 mg/kg METH and 0.9 % NaCl on an alternate day for ten sessions and confined to the corresponding compartment for 30 min meanwhile control mice were given normal saline all day for both compartments. On testing day, either 10 mg/kg CT or 20 mg/kg bupropion (BP), a dopamine reuptake inhibitor, and VTA GABAergic suppressor were orally administered before CPP testing. The results revealed that CPP scores elevation was observed in the METH+vehicle and METH+BP mice, but this was reversed by CT treatment. Although both METH+vehicle and METH+BP enhanced the VTA delta power, NAc gamma I power, NAc delta-gamma coupling, and VTA-NAc gamma I coherence, changes in opposite trends of all mentioned parameters were seen by CT application. These improvements were postulated to involve the antidopaminergic effects of CT via modulations of neural signaling in the VTA and NAc. Altogether, the evidence-based study may suggest the use of CT as alternative drug for METH-seeking and craving therapy.

Neural signaling of methamphetamine craving and seeking intensified by bupropion in the ventral tegmental area-cortico-accumbens circuitry in mice

Previously, bupropion (BUP), a norepinephrine (NE)/dopamine (DA) transporter blocker and nicotinic acetylcholine receptors (nAChRs) antagonist, was found to intensify methamphetamine (METH) craving behaviours in mice. Intense craving causes relapse in drug dependence. This study characterized local field potential (LFP) patterns in the brain regions associated with METH-conditioned place preference (CPP) enhanced by BUP. Male Swiss albino ICR mice were implanted with LFP electrodes to the ventral tegmental area (VTA), medial prefrontal cortex (mPFC) and the nucleus accumbens core (NAcc). Animals received sessions to learn the association between injection effects (1 mg/kg METH and normal saline) with contextual environments (METH- and saline-paired compartments) during the conditioning phase. A total of 20 mg/kg BUP was given to animals before LFP, and behaviour recording in the CPP apparatus during the post-conditioning phase. The results showed that increased CPP scores and % number of entries to the METH-paired zone, as well as changes in VTA, mPFC and NAcc spectral powers and coherence among these areas, were associated with METH-CPP. Treatment with BUP increased VTA delta and gamma I, decreased mPFC alpha, increased NAcc gamma I and decreased gamma II powers. Coherence analyses revealed that BUP decreased gamma II VTA-mPFC and increased beta and gamma I VTA-NAcc connectivity. Altogether, BUP produced additional effects to that of METH-CPP alone. These findings demonstrated changes in neural circuit activities associated with METH-CPP intensified by BUP. Moreover, modulation of NE/DA systems and/or nAChRs actions in the VTA-cortico-accumbens loop might underlie METH craving and dependence.