Anorexigenic effects of two amines obtained from Catha edulis Forsk. (Khat) in rats

Structure-Activity Relationship of Synthetic Cathinones: An Updated Review

The escalating prevalence of new psychoactive substances (NPSs) poses a significant public health challenge, evidenced by the vast chemical diversity, with over 500 substances reported annually to the United Nations Office on Drugs and Crime-Early Warning Advisory (UNODC-EWA) in the past five years. Among NPSs, synthetic cathinones are gaining a lot of popularity among users. Notably, synthetic cathinones accounted for approximately 50% of the total quantity of NPSs reported as seized by EU Member States in 2021. Preliminary data from UNODC indicates that a total of 209 synthetic cathinones have been reported to date. As their popularity grows, studying the structure-activity relationship (SAR) of synthetic cathinones is essential. SAR studies elucidate how structural features impact biological effects, aiding in toxicity prediction, regulatory compliance, and forensic identification. Additionally, SAR studies play a pivotal role in guiding drug policies, aiding authorities in categorizing and regulating newly emerging synthetic cathinones, mitigate public health risks and offer valuable insights into potential therapeutic applications. Thus, our Review consolidates recent findings on the effects of different substitutions in the chemical scaffold of synthetic cathinones on their mechanism of action as well as pharmacological and toxicological effects of synthetic cathinones, thus enhancing understanding of the SAR of synthetic cathinones' pharmacology and potential implications.

Natural products as novel anti-obesity agents: insights into mechanisms of action and potential for therapeutic management

Obesity affects more than 10% of the adult population globally. Despite the introduction of diverse medications aimed at combating fat accumulation and obesity, a significant number of these pharmaceutical interventions are linked to substantial occurrences of severe adverse events, occasionally leading to their withdrawal from the market. Natural products serve as attractive sources for anti-obesity agents as many of them can alter the host metabolic processes and maintain glucose homeostasis via metabolic and thermogenic stimulation, appetite regulation, pancreatic lipase and amylase inhibition, insulin sensitivity enhancing, adipogenesis inhibition and adipocyte apoptosis induction. In this review, we shed light on the biological processes that control energy balance and thermogenesis as well as metabolic pathways in white adipose tissue browning, we also highlight the anti-obesity potential of natural products with their mechanism of action. Based on previous findings, the crucial proteins and molecular pathways involved in adipose tissue browning and lipolysis induction are uncoupling protein-1, PR domain containing 16, and peroxisome proliferator-activated receptor-γ in addition to Sirtuin-1 and AMP-activated protein kinase pathway. Given that some phytochemicals can also lower proinflammatory substances like TNF-α, IL-6, and IL-1 secreted from adipose tissue and change the production of adipokines like leptin and adiponectin, which are important regulators of body weight, natural products represent a treasure trove for anti-obesity agents. In conclusion, conducting comprehensive research on natural products holds the potential to accelerate the development of an improved obesity management strategy characterized by heightened efficacy and reduced incidence of side effects.

Cathinone: An alkaloid of Catha edulis (Khat) exacerbated hyperglycemia in diabetes-induced rats

Cathinone, the main bioactive alkaloid of Catha edulis (khat), slightly increased the blood sugar levels of healthy animals, while its effect on blood sugar levels of diabetic animals has not yet been reported. This study investigated the in vitro inhibition of cathinone on α-amylase and α-glucosidase as well as its in vivo glycemic effects in diabetes-induced rats. Rats were fed on a high fat diet for five weeks, which then intraperitoneally injected with streptozotocin (30 mg/kg). Diabetic rats were distributed randomly into diabetic control (DC, n = 5), 10 mg/kg glibenclamide-treated group (DG, n = 5), and 1.6 mg/kg cathinone-treated group (CAD, n = 5). Additional healthy untreated rats (n = 5) served as a nondiabetic negative control group. Throughout the experiment, fasting blood sugar (FBS), caloric intake and body weight were recorded weekly. By the 28th day of treatment, rats were euthanized to obtain blood samples and pancreases. The results demonstrated that cathinone exerted a significantly less potent in vitro inhibition than α-acarbose against α-amylase and α-glucosidase. As compared to diabetic control group, cathinone significantly increased FBS of diabetic rats, while insulin levels of diabetic rats significantly decreased. In conclusion, cathinone was unable to induce a substantial in vitro inhibition on α-amylase and α-glucosidase, while it exacerbated the hyperglycemia of diabetes-induced rats.

Khat (Catha edulis) upregulates lipolytic genes in white adipose tissue of male obese mice (C57BL/6J)

ETHNOPHARMACOLOGICAL RELEVANCE

Khat (Catha edulis (Vahl) Forssk.) is a herb from the Celastraceae family (also known as qat, gaad, or mirra) that is widely-consumed in East Africa and in the Arabian peninsula. The green leaves and small stems are consumed primarily at recreational and social gatherings, and medicinally for their antidiabetic and appetite-suppression effects.

AIMS

The objectives of this study were to determine the effects of khat and its active alkaloid, cathinone, on food intake and body weight in mice maintained on a high-fat diet, and to investigate its mechanism of action in white adipose tissue and in the hypothalamus.

MATERIALS & METHOD

Adult male mice (C57BL/6J) were fed a high fat diet (HFD) for 8 weeks (n = 30), then divided into 5 groups and treated daily for a further 8 weeks with HFD + vehicle [control (HFD)], HFD + 15 mg/kg orlistat (HFDO), HFD + 200 mg/kg khat extract (HFDK200), HFD + 400 mg/kg khat extract (HFDK400) and HFD + 3.2 mg/kg cathinone (HFDCAT). Treatments were carried out once daily by gastric gavage. Blood and tissue samples were collected for biochemical, hormonal and gene expression analyses.

RESULTS

Khat extracts and orlistat treatment significantly reduced weight gain as compared to control mice on HFD, and cathinone administration completely prevented weight gain in mice fed on HFD. Khat treatment caused a marked reduction in body fat and in serum triglycerides. A dose-dependent effect of khat was observed in reducing serum leptin concentrations. Analysis of gene expression in adipose tissue revealed a significant upregulation of two lipolysis pathway genes:(adipose triglyceride lipase (PNPLA-2) and hormone-sensitive lipase (LIPE). In the hypothalamic there was a significant (P < 0.05) upregulation of agouti-related peptide (AgRP) and cocaine-amphetamine regulated transcript (CART) genes in the HFDK400 and HFDCAT groups.

CONCLUSION

Cathinone treatment blocked body weight gain, while high dose khat extract significantly reduced the weight gain of mice on an obesogenic diet through stimulation of lipolysis in white adipose tissue.

The Appetite Suppressant D-norpseudoephedrine (Cathine) Acts via D1/D2-Like Dopamine Receptors in the Nucleus Accumbens Shell

D-norpseudoephedrine (NPE), also known as cathine, is found naturally in the shrub Catha edulis “Khat.” NPE has been widely used as an appetite suppressant for the treatment of obesity. Although it is known that NPE acts on α1-adrenergic receptors, there is little information about the role of dopamine receptors on NPE’s induced anorectic and weight loss effects. Equally untouched is the question of how NPE modulates neuronal activity in the nucleus accumbens shell (NAcSh), a brain reward center, and a pharmacological target for many appetite suppressants. To do this, in rats, we characterized the pharmacological effects induced by NPE on weight loss, food intake, and locomotion. We also determined the involvement of dopamine D1- and D2-like receptors using systemic and intra-NAcSh antagonists, and finally, we recorded single-unit activity in the NAcSh in freely moving rats. We found that NPE decreased 24-h food intake, induced weight loss, and as side effects increased locomotor activity and wakefulness. Also, intraperitoneal and intra-NAcSh administration of D1 and D2 dopamine antagonists partially reversed NPE’s induced weight loss and food intake suppression. Furthermore, the D1 antagonist, SCH-23390, eliminated NPE-induced locomotion, whereas the D2 antagonist, raclopride, only delayed its onset. We also found that NPE evoked a net activation imbalance in NAcSh that propelled the population activity trajectories into a dynamic pharmacological brain state, which correlated with the onset of NPE-induced wakefulness. Together, our data demonstrate that NPE modulates NAcSh spiking activity and that both dopamine D1 and D2 receptors are necessary for NPE’s induced food intake suppression and weight loss.

Characterization of the Antinociceptive Mechanisms of Khat Extract (Catha edulis) in Mice

This study investigated the antinociceptive mechanisms of khat extract (100, 200, and 400 mg/kg, i.p.) in four pain models: two thermic (hot plate, tail-flick) and two chemical (acetic acid, formalin) models. Male mice were pretreated intraperitoneally (i.p.) with the opioid receptor blocker naloxone (5 mg/kg), the cholinergic antagonist atropine (2 mg/kg), the selective α₁ blocker prazosin (1 mg/kg), the dopamine D₂ antagonist haloperidol (1.5 mg/kg), or the GABA_A receptor antagonist, bicuculline (1 mg/kg) 15 minutes prior to i.p. injection of khat extract (400 mg/kg). Khat extract reduced the nociceptive response of mice in the four pain tests. Naloxone significantly inhibited the antinociceptive effect of khat extract in the hot plate, tail-flick, and the first phase of formalin tests. Bicuculline significantly antagonized the antinociceptive effect of khat extract on the hot plate and tail-flick tests. Haloperidol significantly reversed the antinociceptive effect of khat extract on the tail-flick test and the first phase of formalin test. These results provide strong evidence that the antinociceptive activity of khat extract is mediated via opioidergic, GABAergic, and dopaminergic pathways. The mechanism of the antinociceptive action of khat may be linked to the different types of pain generated in animal models.

Conflicting reports on the role of the glycemic effect of Catha edulis (Khat): A systematic review and meta-analysis

ETHNOPHARMACOLOGICAL RELEVANCE

Traditionally, the leaves of Catha edulis Forsskal (Khat) are consumed by the people of Yemen primarily for its recreational effect, and secondarily, for achieving certain tasks. Additionally, Yemeni diabetics chew such leaves in the belief that this can control their elevated blood glucose level.

AIMS

This review focuses on outlining the findings of studies that have been conducted to display the glycemic effect of Catha edulis, while trying to balance it with findings of the association of its chewing with the development of type 2 diabetes mellitus (DM).

MATERIALS AND METHODS

The search strategy adopted was based on a comprehensive research in Medline, PubMed, Web of Science, JSTOR, Scopus and Cochrane for articles, proceeding abstracts and theses to identify complete reports written in the English language about the glycemic effect of Catha edulis in humans and animals from 1976 to 2016. In addition, bibliographies were also reviewed to find additional reports not otherwise published. Thirty seven records were identified of which, 25 eligible studies were included in the meta-analysis using blood glucose as an outcome measurement. Studies were divided into four subgroups according to the experimental model, namely; non-diabetic animals, diabetic animals, non-diabetic humans and diabetic humans. The pooled mean difference (MD) of blood glucose between experimental and control were calculated using random effects model of the weighted mean difference of blood glucose with 95% confidence interval (CI). Heterogeneity between studies was tested using I(2) statistic and a value of P<0.05 was considered to indicate statistical significance.

RESULTS

The scientific reports in the literature prevailed that the glycemic effect of Catha edulis were greatly conflicting with the majority of studies indicating that Catha edulis has a mild hypoglycemic effect. However, the meta-analysis indicted that the overall result showed an insignificant reduction in blood glucose (MD=-9.70, 95% CI: -22.17 to 2.76, P=0.13, with high heterogeneity between subgroups, I(2)=88.2%, P<0.0001). In addition, pooled mean difference of blood glucose of non-diabetic animals, diabetic animals and non-diabetic humans showed an insignificant reduction in blood glucose (MD=-18.55, 95% CI: -39.55 to 2.50, P<0.08, MD=-52.13%, 95% CI: -108.24 to 3.99, P=0.07 and MD=-2.71%, 95% CI: -19.19 to -13.77, P=0.75) respectively. Conversely, a significant elevation in the pooled mean difference of blood glucose in diabetic humans was indicated (MD=67.18, 95% CI: 36.93-97.43, P<0.0001). The conflict shown in the glycemic effect of Catha edulis is thought to be cultivar-related, while demographic and epidemiological reports suggested that chewing Catha edulis might be a predisposing factor contributing to the development of type 2 DM.

CONCLUSION

It was difficult to draw a meaningful conclusion from both the systematic and the meta-analysis with respect to the glycemic effect of Catha edulis since the meta-analysis results were insignificant with high heterogeneity among subgroups and are greatly conflicting. The variation is most likely due to unadjusted experimental factors or is related to Catha edulis itself, such as the differences in the phytochemical composition. Therefore, it is highly recommended that further studies of the glycemic effect of the cultivar of Catha edulis being studied should come with the identification and quantification of phytochemical content so that a meaningful assessment can be made with regard to its hypoglycemic properties. In addition, well-controlled clinical studies should be conducted to confirm whether or not chewing Catha edulis is associated with the development of type 2 DM, since this would be a source of concern seeing that the plant is widely consumed in certain populations.

Khat (Catha edulis Forsk.) Dependence Potential and Pattern of Use in Saudi Arabia

Background. Catha edulis Forsk. (Khat) is used for its psychoactive effects among people in Africa and the Arabian Peninsula, although its utilization is illegal in some countries such as Saudi Arabia. This study examined the pattern of Khat use and assessed the applicability of the Drug Abuse Screening Test-10 (DAST-10) to measure Khat dependence. Methods. A pretested questionnaire was used to gather data from 603 respondents. Variables included demographic characteristics, pattern of use, reasons for Khat chewing, and DAST-10. Stepwise-logistic regression was used to explore predictors of Khat dependence. Results. The majority of the respondents were married, had a secondary school level of education, were employed, were younger than 35 years old, and were living in rural areas. Many chewers gave more than one reason for using Khat. It was mainly used to increase mental capacity, physical strength, and social entertainment, as well as enhance cheerfulness and orgasms. Statistical modeling of Khat dependence suggested that the most significant predictors were residence (OR = 1.67, P < 0.02), frequency of Khat chewing (OR = 4.8, P < 0.01), age of starting Khat chewing (OR = 1.15, P < 0.01), and time of Khat effect (OR = 1.15, P < 0.04). Conclusion. Our study provides important information on the pattern of Khat use and its potential to cause dependence.

Khat use and appetite: an overview and comparison of amphetamine, khat and cathinone

ETHNOPHARMACOLOGICAL RELEVANCE

To understand the role of khat (Catha edulis) use on the aberrations in appetite and weight which are common comorbidities for khat and other amphetamine users.

MATERIALS AND METHODS

We provide a comprehensive overview and conceptual summary of the historical cultural use of khat as a natural stimulant and describe the similarities and differences between cathinone (the main psychoactive constituent of khat) and amphetamine highlighting the limited literature on the neurophysiology of appetite and subsequent weight effects of khat.

RESULTS

Animal and some human studies indicate that khat produces appetite suppression, although little is known about mechanisms of this effect. Both direct and indirect effects of khat stem from multiple factors including behavioral, chemical and neurophysiological effects on appetite and metabolism. Classic and newly identified appetite hormones have not been explored sufficiently in the study of appetite and khat use. Unique methodological challenges and opportunities are encountered when examining effects of khat and cathinone including khat-specific medical comorbidities, unique route of administration, differential patterns of behavioral effects relative to amphetamines and the nascent state of our understanding of the neurobiology of this drug.

CONCLUSION

A considerable amount of work remains in the study of the appetite effects of khat chewing and outline a program of research that could inform our understanding of this natural amphetamine׳s appetite effects and help prepare health care workers for the unique health effects of this drug.

Acute and sub-chronic effects of purified cathinone from khat (Catha edulis) on behavioural profiles in vervet monkeys (Chlorocebus aethiops)

We investigated the cumulative effects of cathinone on behavioural alterations in single-caged vervet monkeys. Fourteen adult vervets were divided into tests (12 animals) and controls (2 animals), and exposed to escalating doses of cathinone at alternate days of each week for 4 months in presence and absence of cage enrichment. One month of pre-treatment phase served to establish baseline values. Composite behavioural scores of aggression, anxiety, abnormal responses, withdrawal and appetite loss were done. A series of repeated measures analysis of variances were conducted to examine the extent to which cathinone administration was associated with patterns of changes in behavioural data. Results indicate a dose-dependent effect of cathinone on increases of aggression, anxiety, abnormal responses, withdrawal, and appetite loss. The findings demonstrate that at high doses and long-term exposure, cathinone causes behavioural alterations probably via changes in presynaptic striatal dopamine system.

Herbal delivery system for treatment of obesity administration of encapsulated khat-extracts on body weight of rats

SUMMARY

Obesity is one of the most important problems worldwide. Khat (Catha edulis), an evergreen shrub, is thought to reduce body-weight. Its effect is more prominent when khat leaves are chewed. Thus, anti-obesity effects of khat and its associated side effects may depend on the release rate of its active constituents. The present study aimed to investigate the effect of a selected low dose of dried-khat, extracted, formulated as controlled release delivery systems on the body weight (BW), food intake (FI), cholesterol (CS) and triglyceride (TG) levels in rats. Khat extract (KE) was microencapsulated (KE235) and formulated into a parenteral implant (InjKE235). The effects of KE, KE235 and InjKE235 on BW, FI, CS and TG in rats were investigated. The results showed that microcapsules sustained the khat alkaloid release with T50% 1.58 h for KE235 and 14.41 days for InjKE235. KE and KE235 caused maximum reduction in BW, FI, CS and TG during the first to third weeks but rebound gradually thereafter. On the contrary, InjKE235 exhibited a sustained reduction in BW, FI, CS and TG levels for 2 months. The T50% of KE, KE235 and InjKE235 correlated with the reduction in BW, CS and TG but not with FI. In conclusion, the subcutaneous injection and sustained release rate of khat extract play an important role in enhancing the anti-obesity effect in SD rats.:

Subchronic administration of Catha edulis F. (khat) extract is marked by elevation of cardiac biomarkers and subendocardial necrosis besides blood pressure alteration in rats

ETHNPHARMACOLOGICAL RELEVANCE: Khat is a widely chewed herb for its stimulant effect, however, its effects on the cardiovascular system are a source of growing concern, as prevalence of chewing is increasing and susceptible individuals may experience cardiovascular episodes. This study attempted to evaluate cardiovascular substrates that predispose individuals to these episodes by using both biochemical and morphologic-pathologic studies.

MATERIALS AND METHODS

Rats were treated with either Tween 80 (2% in distilled water) (CON), or khat extract (100mg/kg, K100; 200mg/kg, K200; or 400mg/kg, K400 doses) orally for 6 weeks. Blood pressure (BP) in each group was measured before dosing and 1, 2 and 3h after-dose as well as weekly for 6 weeks using Tail cuff method. On day 45, blood was drawn for assessment of cardiac biomarkers and animals were sacrificed, and histological examination was undertaken for any overt damage on the myocardium.

RESULTS

K400 was the only dose that significantly increased BP at 2 (p<0.05) and 3h (p<0.001) postdose compared to predose level. Likewise, the 3h postdose BP of each week was significantly greater (p<0.001) than baseline BP only at 400mg/kg. However, when the weekly values were compared among themselves, the difference was not statistically significant and a progressive change in postdose BP had not been observed. On the other hand, predose systolic BP of K400 rats tended to decline at week 3 and significantly decreased (p<0.05) beyond week 4 compared to baseline values, but the decline was not significant for the rest of the doses. Biomarker assessments revealed that whereas levels of total creatine kinase were found to be elevated significantly for K100 (p<0.05), K200 and K400 (p<0.001 in both cases); aspartate aminotransferease was increased in K200 (p<0.01) and K400 (p<0.001) compared to CON rats. By contrast, levels of cardiac troponin T was significantly increased (p<0.001) only in K400 rats. Heart tissues of CON and K100 rats were normal, while those from K200 showed signs of focal lesions but normal architecture of the myocardium was maintained. K400 rats, however, displayed fragmentation and segmentation of fibers, edema and mottled staining.

CONCLUSIONS

These findings collectively indicate that the high dose of crude khat extract modulated most of the hemodynamic, biochemical and histopathological parameters in rats and hence chronic use of khat at higher dose and for longer sessions bear a significant risk for cardiovascular morbidities.

Phytochemicals in the Control of Human Appetite and Body Weight

Since obesity has grown to epidemic proportions, its effective management is a very important clinical issue. Despite the great amount of scientific effort that has been put into understanding the mechanisms that lead to overconsumption and overweight, at the moment very few approaches to weight management are effective in the long term. On the other hand, modern society is also affected by the growing incidence of eating disorders on the other side of the spectrum such as anorexia and bulimia nervosa which are equally difficult to treat. This review will try to summarise the main findings available in the literature regarding the effect of plants or plant extracts (phytochemicals) on human appetite and body weight. The majority of plant extracts are not single compounds but rather a mixture of different molecules, therefore their mechanism of action usually targets several systems. In addition, since some cellular receptors tend to be widely distributed, sometimes a single molecule can have a widespread effect. This review will attempt to describe the main phytochemicals that have been suggested to affect the homeostatic mechanisms that influence intake and body weight. Clinical data will be summarised and scientific evidence will be reviewed.

The effect of Khat (Catha edulis) as an appetite suppressant is independent of ghrelin and PYY secretion

BACKGROUND

The leaves of the khat plant (Catha edulis) are chewed for their pleasurable effects. Chewing releases cathinone which may decrease appetite through an unknown mechanism. Levels of the peptide ghrelin increase with hunger and decrease immediately post-prandially, while peptide YY is released following a meal. We hypothesised that the anorexigenic effects of khat may be mediated through changes in these hormones.

MATERIALS AND METHODS

Six habitual khat chewers attended on two separate occasions. For a period of 3h they chewed either khat leaves or lettuce. Blood pressure (BP) and pulse rate (PR) were monitored throughout, as were subjective assessments of hunger and fullness. Plasma samples were analysed for cathinone, ghrelin and PYY levels.

RESULTS

Chewing khat significantly decreased subjective feelings of hunger and increased fullness (p<0.05) but had no effect on ghrelin and PYY levels. Khat led to an increase in cathinone levels as well as an increase in BP and PR. Cathinone levels correlated positively with fullness and pulse rate and negatively with hunger.

CONCLUSIONS

Chewing khat decreases subjective feelings of hunger and increases systemic sympathetic tone, but has no effect on ghrelin and PYY levels. We conclude that the anorexigenic effect of khat may be secondary to central mechanisms mediated via cathinone.

A review of the neuropharmacological properties of khat

BACKGROUND

The psychostimulant khat (Catha edulis Forsk), is a herbal drug cultivated and chewed as a recreational and socializing drug in East Africa and the Arabian Peninsula for centuries. Due to increasing air transportation and the loosening of customs restrictions, it is now readily available in the Western Countries mainly used by immigrants from khat growing areas causing a concern to policy-makers.

OBJECTIVE

We conducted this review to further gain an insight to the neuropharmacological effects of khat.

METHODOLOGY

PubMed search engine with key terms 'khat' or 'qat' or 'mirra' or'qaad/jaad' or 'cathinone' was used to obtain articles relevant to khat chewing. In total 284 English written articles published from 1959 to 2007 were screened.

RESULTS

Most of the studies focused on cathinone, the postulated active psychostimulant alkaloid in khat. There were few studies which investigated the entire plant extract in either in vitro or animal studies. In the majority of the studies it was reported that both cathinone and cathine, another psychoactive constituent, have actions that are similar to those of amphetamine.

CONCLUSIONS

It seems that the well investigated khat alkaloids have many features similar to amphetamines; however there is a need for a more thorough examination of khat itself in well designed in vitro, animal and human studies with a range of comparator drugs before confirming the claim that khat is a "natural amphetamine".

Khat (Catha edulis)-an updated review

The habit of chewing fresh leaves and twigs of khat (Catha edulis) for their stimulating amphetamine-like effects is highly prevalent in East Africa and southwest on the Arabic peninsula. There is an extensive literature on khat providing information about its history, botany, production, geographical distribution, chemistry and pharmacology, and exploring the social, economic, medical, psychological and oral aspects related to its use. Some of this literature dates as early as the 11th century; however, most of it appeared after the first scientific description of khat by Peter Forskal in 1775. This review provides a panorama of khat and the various aspects of its use. A non-technical description of the plant chemistry and pharmacology is included. The medical, psychological and oral aspects are emphasized, and the current knowledge about the microbiological effects of khat is also presented.

Exploration of adverse psychological symptoms in Yemeni khat users by the Symptoms Checklist-90 (SCL-90)

AIM

The present study was aimed at assessing associations between psychological symptoms and khat use in the Yemeni population.

SETTING

The survey was performed in 2000/2001, in different zones including three urban and three rural areas.

PARTICIPANTS

The survey was carried out in 800 Yemeni adults (15-76), both male and female, representing mainly urban populations of students, state employees and housewives.

DESIGN

A cross-sectional survey was undertaken using face-to-face interviews and no preset selection criteria regarding profession, socio-economic status, age or gender.

MEASUREMENT

The Symptoms Checklist-90 (SCL-90) was used containing 90 items, which cover nine scales of the following domains: somatization, depression, anxiety, phobia, hostility, interpersonal sensitivity, obsessive-compulsive, hostility, interpersonal sensitivity, paranoia and psychoticism. Details of khat use and socio-demographic data were also collected.

FINDINGS

At least one life-time episode of khat use was reported in 81.6% of men and 43.3% of women. Male users tended to use more frequently. The incidence of adverse psychological symptoms was not greater in khat users; in fact, there was a negative association between the incidence of phobic symptoms and khat use.

CONCLUSIONS

Khat use is very common in the Yemeni population, particularly men, but it is not associated with adverse psychological symptoms.

Coronary and aortic vasoconstriction by cathinone, the active constituent of khat

1. The psychostimulant constituent of khat leaves, S-(-)-cathinone, was examined for vascular activity on the coronary vasculature of guinea-pig-isolated perfused hearts and aortic ring preparations. 2. Cathinone caused coronary vasoconstriction, negative inotropy and negative chronotropy in isolated hearts. The major metabolite of cathinone after its ingestion, 1R.2S-(-)-norephedrine (norephedrine), also caused coronary vasoconstriction comparable with that by cathinone. Norephedrine, however, had no effect on force or rate of cardiac contractions. 3. Cocaine (10 microm) potentiated the coronary vasoconstriction and positive inotropy by noradrenaline indicating inhibition of neuronal uptake. The vasoconstriction and negative inotropy by cathinone, however, were not affected, indicating that its action was not via release of noradrenaline from sympathetic neurones. 4. The alpha(1)-adrenoceptor antagonist, prazosin, blocked the vasoconstriction by noradrenaline, but not that produced by cathinone in the presence of cocaine. This indicates that the coronary vasoconstriction by cathinone was not due to an action on alpha(1)-adrenoceptors either directly or indirectly through noradrenaline release. 5. Three repeated doses of cathinone displayed the same coronary vasoconstrictor responses, indicating a lack of tachyphylaxis and therefore confirming that the response was unlikely to be due to indirect sympathomimetic activity through release of noradrenaline. 6. In guinea-pig aortic rings, the order of vasoconstrictor activity was: noradrenaline > norephedrine > cathinone, with each causing approximately equivalent maximum responses. The time to reach plateau contractions was shortest for noradrenaline (5.1 +/- 0.5 min), then norephedrine (9.3 +/- 1.5 min) and cathinone the longest (25.4 +/- 3.2 min, 335 microm dose). 7 These results indicate that cathinone has vasoconstrictor activity which is not due to indirect or direct sympathomimetic activity. The precise mechanism for this vasoconstriction remains to be determined. The coronary vasoconstriction may explain the increased incidence of myocardial infarction in khat chewers, which may arise from coronary vasospasm.

Plants and the central nervous system

This review article draws the attention to the many species of plants possessing activity on the central nervous system (CNS). In fact, they cover the whole spectrum of central activity such as psychoanaleptic, psycholeptic and psychodysleptic effects, and several of these plants are currently used in therapeutics to treat human ailments. Among the psychoanaleptic (stimulant) plants, those utilized by human beings to reduce body weight [Ephedra spp. (Ma Huang), Paullinia spp. (guaraná), Catha edulis Forssk. (khat)] and plants used to improve general health conditions (plant adaptogens) were scrutinized. Many species of hallucinogenic (psychodysleptic) plants are used by humans throughout the world to achieve states of mind distortions; among those, a few have been used for therapeutic purposes, such as Cannabis sativa L., Tabernanthe iboga Baill. and the mixture of Psychotria viridis Ruiz and Pav. and Banisteriopsis caapi (Spruce ex Griseb.) C.V. Morton. Plants showing central psycholeptic activities, such as analgesic or anxiolytic actions (Passiflora incarnata L., Valeriana spp. and Piper methysticum G. Forst.), were also analysed.Finally, the use of crude or semipurified extracts of such plants instead of the active substances seemingly responsible for their therapeutic effect is discussed.

Pharmacological approaches for the treatment of obesity

The high incidence of obesity, its multifactorial nature, the complexity and lack of knowledge of the bodyweight control system, and the scarcity of adequate therapeutics have fuelled anti-obesity drug development during a considerable number of years. Irrespective of the efforts invested by researchers and companies, few products have reached a minimum level of effectiveness, and even fewer are available in medical practice. As a consequence of anti-obesity research, our knowledge of the bodyweight control system increased but, despite this, the pharmacological approaches to the treatment of obesity have not resulted yet in effective drugs. This review provides a panoramic of the multiple different approaches developed to obtain workable drugs. These approaches, however, rely in only four main lines of action: control of energy intake, mainly through modification of appetite;control of energy expenditure, essentially through the increase of thermogenesis;control of the availability of substrates to cells and tissues through hormonal and other metabolic factors controlling the fate of the available energy substrates; andcontrol of fat reserves through modulation of lipogenesis and lipolysis in white adipose tissue. A large proportion of current research is centred on neuropeptidic control of appetite, followed by the development of drugs controlling thermogenic mechanisms and analysis of the factors controlling adipocyte growth and fat storage. The adipocyte is also a fundamental source of metabolic signals, signals that can be intercepted, modulated and used to force the brain to adjust the mass of fat with the physiological means available. The large variety of different approaches used in the search for effective anti-obesity drugs show both the deep involvement of researchers on this field and the large amount of resources devoted to this problem by pharmaceutical companies. Future trends in anti-obesity drug research follow closely the approaches outlined; however, the increasing mass of information on the molecular basis of bodyweight control and obesity will in the end prevail in our search for effective and harmless anti-obesity drugs.

Effect of (-)-cathinone, a psychoactive alkaloid from khat (Catha edulis Forsk.) and caffeine on sexual behaviour in rats

The effect of (-)-cathinone, caffeine and their combinations was studied on the sexual behaviour of male rats. Male sexual activities were assessed by recording the erectile responses (grooming of genitalis, yawning/stretching and homosexual mounting), in the absence of females. The copulatory behaviour was observed by caging males with receptive females brought into oestrus with s.c. injection of oestradiol benzoate and progesterone. The copulatory pattern of male rats (mounting, intromissions, ejaculations and refractory period) was recorded. The oral treatment of cathinone (5 mg kg-1 day-1), caffeine (50 mg kg-1 day-1) and their combinations for 15 days increased arousal (motivation) in male rats as evidenced by increased mounting performance and anogenital investigatory behaviour. However, erectile and ejaculatory responses, measured in the present study, showed no stimulant effect. It is conceivable from the present results that cathinone, the psychostimulant constituent of khat modified masculine pattern behaviour and caffeine also changed the effect of cathinone when administered concomitantly. However, our data provide no evidence that cathinone could be considered as an aphrodisiac.

Khat chewing delays gastric emptying of a semi-solid meal

BACKGROUND

The leaves of Khat are chewed for their central stimulant effect, but their use may cause anorexia and constipation.

METHODS

Gastric emptying of a radio-labelled semi-solid meal was measured in 12 healthy volunteers on two occasions a week apart. Subjects chewed either Khat leaves (Catha edulis) or lettuce for 2 h before the study.

RESULTS

Gastric emptying was significantly (P < 0.02) prolonged after chewing Khat compared with lettuce.

CONCLUSION

The sympathomimetic action of cathinone in Khat may cause the observed delay in gastric emptying.

Evaluation of teratogenic potential of khat (Catha edulis Forsk.) in rats

The embryotoxic and teratogenic effects of khat (Catha edulis Forsk.), a plant chewed by the people of Eastern Africa and Southern Arabia to attain a state of euphoria and stimulation, was studied in Wistar rats. Methanolic extract of khat was administered orally by gavage to rats during days from 6 to 15 of gestation at doses of 0, 125, 250 and 500 mg/kg. body weight/day. Khat reduced the food consumption and maternal weight gain and also lowered the food efficiency index, as compared to control mothers. On day 20 of gestation, all dams were sacrificed by cervical dislocation, cesarean sections were performed and maternal and fetal toxicities were assessed. The administration of khat had no effect on fetal sex ratio. However, at a dose of 125 mg/kg body weight and above, it produced a significant increase in resorptions and fetal wastage. Khat administration in utero also reduced the litter size and caused intrauterine growth retardation. External, visceral and skeletal examination of the fetus of treated dams showed several types of malformations and variations in all the groups of animals. However, a consistent tendency of abnormalities was observed in the highest dosed (500 mg/kg) group. The data of the present study revealed that khat retarded fetal growth and induced terata. The present observations indicate that khat possesses both embryotoxic as well as teratogenic properties. The developmental toxicities of khat are dose-related.

Cathinone, a natural amphetamine

Cathinone is an alkaloid that has been discovered some fifteen years ago in the leaves of the khat bush. This plant grows in East Africa and in southern Arabia, and the inhabitants of these regions frequently chew khat because of its stimulating properties. Cathinone, which is S(-)-alpha-aminopropiophenone, was soon found to have a pharmacological profile closely resembling that of amphetamine; indeed, in a wide variety of in vitro and in vivo experiments it was demonstrated that cathinone shares the action of amphetamine on CNS as well as its sympathomimetic effects; thus, for example, drug-conditioned animals will not distinguish between cathinone and amphetamine. These various observations were confirmed by a clinical experiment showing that cathinone also in humans produces amphetamine-like objective and subjective effects. Finally, it was demonstrated that cathinone operates through the same mechanism as amphetamine, i.e. it acts by releasing catecholamines from presynaptic storage sites. Thus, much experimental evidence indicates that cathinone is the main psychoactive constituent of the khat leaf and that, in fact, this alkaloid is a natural amphetamine.

Dopaminergic nature of acute cathine tolerance

Cathine is a psychoactive constituent in the leaves of the Khat shrub which are habitually ingested for their stimulatory effects in many parts of the world. Rats were trained to discriminate the stimulus effect of intraperitoneally administered 4.8 mg/kg d-cathine and, once trained, administration of another Khat constituent, cathinone, was shown to produce cathine-like effects. This generalization to cathinone was dose-responsive when testing occurred 24 hr after vehicle administration, whereas prior administration of cathine resulted in a diminished discriminative response to subsequent cathinone administration possibly as a result of the development of acute tolerance. CGS 10746B, a compound that blocks presynaptic release of dopamine, significantly decreased rats' ability to discriminate cathine when it was administered 25 min prior to cathine testing and it reversed the acute tolerance observed when cathine was tested 24 hr after cathine administration. These results indicate that a previously reported acute tolerance effect to cathine after cathinone administration in cathinone-trained rats appears to be symmetrical in that there is acute tolerance to cathinone after cathine in these cathine-trained rats. The results with CGS 10746B would suggest that both the cathine-induced discriminative cue and cathine's ability to produce acute tolerance are mediated by presynaptic dopamine release.

Discriminative stimulus properties of (+)cathine, an alkaloid of the khat plant

The effects of the psychostimulant (+)cathine (norpseudoephedrine) were examined in a two-choice, food-motivated, drug-discrimination paradigm. Rats were able to discriminate cathine from vehicle and this effect was dose- and time-dependent. Prior administration of cathine resulted in a diminished response (tolerance) to subsequent cathine and this effect developed and dissipated rapidly. Thus, different dose-response curves were generated depending upon whether cathine or vehicle was administered the day before testing. The development of tolerance also shortened cathine's time course of action and enhanced the ability of haloperidol to antagonize the cathine cue. These results suggest caution in interpreting effects produced by intermittent drug injection schedules.

Enantiomers of phenylpropanolamine suppress food intake in hyperphagic rats

Phenylpropanolamine (PPA, d,l-norephedrine), available in many over-the-counter nasal decongestants and appetite suppressants, is a racemic mixture of the enantiomers d- and l-norephedrine. The present study evaluates the effects of the individual PPA enantiomers on a variety of nondrug (food deprivation) and drug-induced hyperphagias (2-deoxyglucose and insulin). Racemic PPA has been shown to significantly suppress food intake in these hyperphagic models. Both l-norephedrine (5-50 mg/kg) and d-norephedrine (5-150 mg/kg), administered intraperitoneally, significantly suppressed feeding after a 4-hr fast during the dark cycle. During the light period, l-norephedrine (7.5, 10, 15 mg/kg) and d-norephedrine (75, 100, 150 mg/kg) significantly reduced food intake at the 1-hr and 3-hr time intervals in the 24-hr food deprivation-, insulin- and 2-deoxyglucose-induced hyperphagic models. Only 7.5 mg/kg l-norephedrine in the insulin-induced hyperphagia at 3 hr failed to significantly suppress feeding. These results indicate that each individual PPA enantiomer possesses the ability to suppress food intake in rats made hyperphagic by various stimuli.

An evaluation of the male reproductive toxicity of cathinone

(-)-Cathinone is the major psychoactive component of khat plant (Catha edulis Forssk.). Khat has been shown to produce reproductive toxicity in human beings and experimental animals. However, the chemical constituents of khat leaves responsible for sexual dysfunction are not known. In the present study cathinone enantiomers have been investigated for their reproductive toxicity in rats. Cathinone produced a dose-dependent decrease in food consumption and suppressed the gain in body weight. There was a significant decrease in sperm count and motility and increase in the number of abnormal sperms in cathinone treated animals. Histopathological examination of testes revealed degeneration of interstitial tissue, cellular infiltration and atrophy of Sertoli and Leydig's cells in cathinone treated animals. Cathinone also produced a significant decrease in plasma testosterone levels of the rats. Although both enantiomers of cathinone produced deleterious effects on male reproductive system, (-)-cathinone was found to be more toxic. From this study it may be concluded that the cathinone content in khat may be partially or totally responsible for the reproductive toxicity in khat chewers.

Rats become acutely tolerant to cathine after amphetamine or cathinone administration

The drug discrimination paradigm was used to evaluate in rats the ability of the discriminate response to either 0.8 mg/kg d-amphetamine or 0.8 mg/kg l-cathinone to generalize to 2.4-6.0 mg/kg of the active cathinone metabolite d-norpseudoephedrine, also known as cathine. When tested 24 h after vehicle administration, cathine generalized in a dose-related fashion in rats (n = 6) trained with cathinone (ED50 = 3.03 mg/kg) and in rats (n = 8) trained with amphetamine (ED50 = 2.93 mg/kg). In contrast, when cathine was tested 24 h after the administration of either amphetamine or cathinone, it produced significantly decreased discriminative performance. The possibility that this acute tolerance may have been produced by release, and subsequent depletion, of brain dopamine was tested by pretreating rats with the dopamine release inhibitor CGS 10746B. When CGS 10746B was administered prior to cathinone it significantly decreased cathinone discrimination. In addition, acute tolerance to cathine at 24 h after vehicle-cathinone co-administration was reversed when cathine was tested 24 h after CGS 10746B-cathinone co-administration. The results suggest that cathinone-produced discriminative stimulus, as well as the acute tolerance to cathine, may be dopaminergically mediated.

Pharmacological properties of the stimulant khat

The chewing of the stimulant leaf khat is a habit that is widespread in certain countries of East Africa and the Arabian peninsula. During the last decade, important progress has been made in understanding the pharmacological basis for the effects of khat. It is now known that the CNS action of this drug is due to the presence of the alkaloid cathinone, and the results of various in vitro and in vivo experiments indicate that this substance must be considered a natural amphetamine. It is the purpose of the present review to describe briefly the khat habit and to summarize the pharmacology of khat and of its active constituents.

Comparative study of cathinone and amphetamine on brown adipose thermogenesis

The effect of cathinone and amphetamine on brown adipose tissue thermogenesis and its modification with propranolol and timolol has been studied in rats. Both cathinone and amphetamine produced significant dose dependent increases in intracapsular brown adipose tissue (IBAT) and rectal temperatures. Amphetamine was found to be three times more potent as compared to cathinone, on a dose basis. Pretreatment of animals with propranolol and timolol individually inhibited cathinone and amphetamine induced hyperthermia. These findings suggest the involvement of beta adrenergic receptors in cathinone and amphetamine induced thermogenesis.

Khat consumption: a pharmacological review

The present review deals with the considerable body of evidence gathered in the last ten years on the clinical and experimental pharmacology of Khat. Khat effects are generally agreed to be of amphetamine-like type. In particular, Khat ingestion, like amphetamine ingestion, produces sympathetic activation, anorexia, euphoria, increased intellectual efficiency and alertness. These effects are mainly mediated by phenylalkylamines, such as cathinone and cathine, because the pharmacological actions of these agents and those produced by amphetamine almost overlap. In infra-human species cathinone is an effective positive reinforcer (i.e., it maintains self-administration). However, it would be inappropriate to infer from cathinone and cathine effects assessed in animals a high potential of abuse for Khat in humans; apart from other reasons the bulk volume of Khat leaves, limits the ingestion of high quantities of the active principles. Accordingly, in habitual consumers Khat dependence is probably mild, because craving and tolerance to the sympathomimetic and neuroendocrine effects of Khat are present, but there is no definite abstinence syndrome. Therefore, in our opinion, policies restricting the use of Khat should be adopted with caution, lest they simply change the pattern of drug abuse and increase the spread of more dangerous drugs.

A comparison of the effects of phenylpropanolamine, d-amphetamine and d-norpseudoephedrine on open-field locomotion and food intake in the rat

d,l-Norephedrine (PPA) is available as an over-the-counter appetite suppressant and nasal decongestant in the U.S.A. The pseudoisomer d-norpseudoephedrine, is available as an appetite suppressant in Europe, and has been isolated as one of the stimulatory components (cathine) of the Khat plant. Some authors have misidentified cathine as PPA and this confusion in the literature has resulted. PPA and d-norpseudoephedrine possess significantly different pharmacological properties despite having identical structural formulae. Anorectic activity was determined in a food-deprived rat model. PPA and d-norpseudoephedrine were approximately one-tenth as potent as d-amphetamine with all compounds producing a dose-dependent decrease in food intake. Locomotor activity in an open-field apparatus was determined as an index of CNS stimulation. Male Sprague-Dawley rats treated with d-norpseudoephedrine, in doses between 10 and 50 mg/kg, exhibited significantly increased locomotor scores compared to saline (control) treated animals, an increase similar to that caused by 2 mg/kg d-amphetamine. PPA (5-50 mg/kg) failed to increase locomotion significantly. These results indicate that although each compound tested decreased food intake in a dose-dependent fashion, significant differences in open-field locomotion do exist between PPA, d-norpseudoephedrine, and d-amphetamine. Stereoisomeric compounds, although structurally similar, frequently have different pharmacological effects. Thus extreme care must be taken to properly identify these compounds in the literature.

Experimental manipulations of eating: advances in animal models for studying anorectic agents

The material set out in this text has been designed to show the wide range of procedures which have the capacity to modify eating behavior--to produce hyper- or hypophagia, to alter the profile of eating patterns, or to adjust dietary preferences and selection. Accordingly, in investigating anorectic drugs it seems necessary to observe the effects of drug actions in a variety of experimental models. This strategy will provide a more complete description of the effect of a drug, will throw light on the mechanism of action, and will provide a more realistic base for predicting the effects of drugs in man.

Dopaminergic mediation of a behavioral effect of l-cathinone

Ten male rats were trained to discriminate between the stimulus properties of 0.6 mg/kg l-cathinone and saline in a two-lever food-motivated operant task. Once trained, rats showed a dose-dependent increase in discrimination over a dosage range of 0.15-1.2 mg/kg l-cathinone. Analysis of this dose-response relationship indicated an ED50 of 0.27 mg/kg. Pretreatment with 0.2 mg/kg of the specific dopamine blocking drug haloperidol increased this ED50 to 0.47 mg/kg and significantly decreased discriminative performance when co-administered with either 0.15, 0.3, or 0.6 mg/kg l-cathinone. Since the dose-effect curves for cathinone with and without haloperidol pre-treatment were parallel, it is suggested that l-cathinone, the active constituent in khat, produces its discriminative properties, in part, by mediation of dopaminergic neuronal systems.

Induction of and recovery from tolerance to the discriminative stimulus properties of l-cathinone

Rats previously trained to discriminate between 0.6 mg/kg l-cathinone and saline in a two-lever, food-motivated operant task were administered l-cathinone at the same dose, every 8 hours for 10 days. Discrimination testing during this chronic administration phase of experimentation indicated that the animals' ability to discriminate both 0.3 and 0.6 mg/kg l-cathinone decreased when compared to their discriminative ability prior to chronic administration. In contrast, discrimination of the non-drug state, i.e., saline, was not affected. Comparison of dose-response curves prior to and during chronic cathinone administration indicated a 3-4 fold shift to the right for the latter curve. Continued testing after termination of chronic treatment resulted in a return to pre-chronic discriminative performance by the fifteenth day after cessation. These results indicate that tolerance to the discriminative effects of l-cathinone can be produced within 10 days of chronic administration and recovery from this observed tolerance occurs within 15 days of cessation of chronic administration.

A review of the effects of repeated administration of selected phenylethylamines

Several phenylethylamines are under consideration for international control. The effects of repeated administration of these compounds, including tolerance, physical dependence and central nervous system (CNS) toxicity, are reviewed here. The compounds can be divided into two major chemical groups: those with substituents on the ethylamine portion of the molecule and those with substituents on the phenyl ring. Although the effects of repeated administration have not been directly determined for most of the compounds, certain representative compounds of each chemical group have been examined in some detail. Prominent among the effects of repeated administration are CNS toxicity and tolerance development. Physical dependence has not been reported for any of these compounds. Future research with these compounds should emphasize the investigation of the CNS toxicity and the functional consequences of such effects for the organism.

Comparative discriminative stimulus properties of dl-cathinone, d-amphetamine, and cocaine in rats

The discriminative stimulus properties of dl-cathinone (dl-CAT), d-amphetamine (d-A), and cocaine (COC) were compared and effects of haloperidol pretreatment on these properties were studied in rats. The ED50's of each drug were also determined. Stimulus generalization (i.e., greater than 75% of responses occurring on the drug lever) occurred with each of the three training drugs to all three test drugs. The degree of generalization was less between d-amphetamine and dl-cathinone than between d-amphetamine and cocaine or between cocaine and dl-cathinone. No significant differences were observed among the ED50's of each test drug obtained in all three training groups. Pretreatment with haloperidol failed to alter the stimulus properties of dl-cathinone. Haloperidol administration did partially antagonize the stimulus complex induced by d-amphetamine and cocaine. It is concluded that all three agents share somewhat similar but not identical, stimulus properties. The stimulus properties of the training dose of d-amphetamine may be somewhat different from those of dl-cathinone and may be more dependent on functional dopaminergic pathways.

Discriminative properties of the psychostimulant dl-cathinone in a two lever operant task. Lack of evidence for dopaminergic mediation

In order to analyse further the discriminative stimulus properties of stimulant drugs, rats were trained to discriminate 2.0 mg/kg of dl-cathinone in a two-lever operant task. Dose-related generalization was seen to cathinone itself and to a wide range of stimulant drugs including d-amphetamine, cocaine, methylphenidate, pipradrol and cathine, i.e. (+)norpseudoephedrine. The high degree of specificity of the cathinone cue at the specific training dose studied was shown by the fact that the following nonstimulant drugs failed to generalize at all to cathinone, even in large doses--haloperidol, chlordiazepoxide, fenfluramine and fentanyl. The cathinone cue at 2.0 mg/kg was probably of central origin because phydroxyamphetamine (a polar congener of amphetamine) failed to generalize to cathinone at a dose nearly 50 times the ED50 for amphetamine generalization. Phenylethylamine (PEA; alpha-demethylamphetamine) and deuterated phenylethylamine (alpha, alpha, d2-PEA), a long acting derivative of phenylethylamine which is resistant to metabolism by monoamine oxidase, produced at most partial (60%) generalization to cathinone, even in large doses. alpha-Demethylcathinone failed to generalize at all to cathinone at doses up to 10 times the ED50 for cathinone. Thus, the alpha-methyl groups of both amphetamine and cathinone are important in determining their cue properties. The involvement of dopaminergic systems in the cathinone cue was investigated by examining generalization to apomorphine and antagonism by haloperidol. Apomorphine produced at most 29% generalization to cathinone. Haloperidol, at doses up to 0.3 mg/kg, produced at most 50% antagonism of both the cathinone cue and of the ability of amphetamine to substitute for cathinone. It is suggested that the evidence for dopaminergic mediation of the cue properties of cathinone and of other CNS stimulants is somewhat tenuous, whilst endogenous phenylethylamine may play some part in the mediation of the stimulant cue. Haloperidol, alone and in conjunction with amphetamine or cathinone, produced a remarkable tendency for subjects to emit a greater proportion of their total responses on the inoperative rather than the operative lever than was seen after saline or injections of vehicle. This action of a neuroleptic drug suggests, in accordance with Colpaert, Niemegeers and Janssen (1977), that in drug discrimination antagonism studies involving neuroleptics, and perhaps other drugs, quantal (lever selection) rather than quantitative (percentage of responses on the drug lever) indices may be the procedures of choice.

Comparative effects of cathinone and amphetamine on fixed-interval operant responding: a rate-dependency analysis

The actions of dl-cathinone and d-amphetamine on operant responding were compared in rats. The effects of both drugs were predominantly suppressive on behaviour maintained by a Fixed Interval 2 minutes schedule of reward. Both drugs had equivalent durations of action in suppressing responding. The actions of the two compounds could be described as rate-dependent, although their rate-dependent actions could most parsimoniously be attributed to drug-induced rate constancy. Methysergide (10 mg/kg) had no significant differential effect on the response suppressant effects of the two compounds, even though in vitro studies have indicated that cathinone and amphetamine differ in their serotonin receptor affinity. The actions of cathinone were qualitatively similar to those of amphetamine in this behavioural test. Furthermore the observed potency ratio for dl-cathinone to d-amphetamine (1:3) was similar to that reported elsewhere in a range of other behavioural tests (anorexia, adipsia, drug-induced rotation, lethality) for this pair of isomers. The only major difference reported to date between the behavioural actions of cathinone and amphetamine relates to the unexpectedly weak potency of cathinone in the conditioned taste aversion procedure. Cathinone, the major active constituent of the Khat plant, is therefore a psychostimulant drug which may possess potent reinforcing properties by virtue of its amphetamine-like stimulant actions coupled with its very weak aversive properties.

The puzzle of drug-induced conditioned taste aversion: comparative studies with cathinone and amphetamine

The potency of dl-cathinone (the active constituent of the Khat plant) was compared with that of d-amphetamine in the conditioned taste aversion (C.T.A.) procedure and in a test of drug-induced adipsia in rats. Both drugs induced C.T.A., the potency ratio being 1:17 (amphetamine was more potent). Both drugs induced adipsia in deprived rats given access to water for 120 min. The potency ratio in this procedure was 1:4. Potency in the C.T.A. procedure did not therefore correlate with potency in inducing adipsia; consequently drug-induced C.T.A. cannot be attributed to conditioned adipsia. In the adipsia test the drugs had similar durations of action, thus factors related to duration of drug action (cf Cappell and Le Blanc 1977) cannot account for the surprisingly low potency of cathinone in the C.T.A. procedure. These data, obtained with stimulant drugs with similar structures and similar actions in a variety of conventional in vivo and in vitro pharmacological tests, illustrate the unpredictable nature of drug actions in the C.T.A. procedure. The low potency of cathinone in inducing C.T.A. could not be predicted from knowledge of the potency of this compound in tests of adipsia (as shown here) or (as reported elsewhere) in tests of anorexia, locomotor stimulation, stereotypy, suppression of operant responding, drug discrimination, release and inhibition of reuptake of dopamine and noradrenaline, lethality and actions on the cardiovascular system. All of these studies have reported potency ratios considerably lower than 1:17, which were nevertheless similar to the 1:4 ratio observed in the adipsia test.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of dl-cathinone, d-amphetamine and cocaine on avoidance responding in rats and their interactions with haloperidol and methysergide

The effects of dl-cathinone (dl-CAT), d-amphetamine (d-A), and cocaine (COC) on conditioned shock avoidance responding and their interactions with haloperidol and methysergide on this behavior were studied in male Wistar rats. All three stimulants produced significant increases in intertrial interval (ITI) responding and in the number of avoidance responses and a decrease in avoidance latencies. These actions were antagonized by pretreatment with haloperidol (0.07 and 0.15 mg/kg, IP). Pretreatment with methysergide (1.0 and 2.0 mg/kg, IP) increased the effects of all three stimulants on ITI responding, but not on the other two parameters. These results suggest that the effects of these stimulants on avoidance responding may be mediated by dopaminergic systems. In addition, these stimulant-induced changes on ITI responding probably also involve actions on serotonergic systems.

Preference in rhesus monkeys given a choice between cocaine and d,l-cathinone

Previous experiments have shown that both cocaine and d,l-cathinone can function as positive reinforces when delivered intravenously to rhesus monkeys. However, the relative reinforcing efficacies of these compounds have not been established. In the present experiment, three rhesus monkeys were allowed to choose between saline and several doses of d,l-cathinone or cocaine as well as between several doses of both drugs in a discrete-trial choice procedure. Sufficient doses (.05 to .2 mg/kg/injection) of either drug maintained self-administration and the higher doses were reliably preferred to saline. Doses of d,l-cathinone that were preferred to saline were then compared to a range of cocaine doses in drug-drug choice. As the dose of d,l-cathinone that was available was increased, an increase in cocaine dose was necessary to maintain cocaine preference. Comparison of drug-drug choice data to dose combinations predicted to be chosen with equal frequency revealed that the reinforcing efficacy of d,l-cathinone was equivalent to that of cocaine.