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IntroductionIn east African countries and southwestern part of the Arabian Peninsula, there is a deeply rooted cultural practice of chewing the fresh leaves and twigs of the shrub Catha edulis Forsk (khat) for its psychostimulant effects, which are comparable to amphetamines. An estimated 20 million people including children chew khat regularly (Patel, 2015). The WHO does not consider khat to be a seriously addictive drug (WHO, 2008), and in ranking of 20 popular recreational drugs, khat was ranked 17th in dependence (Nutt et al. 2007).

In the Conditioned Place Preference (CPP), a Pavlovian conditioning test, the animal learns to associate a distinct environment in the drug-induced state and another with drug-free state. The time the animal spends in the drug-paired environment after conditioning is a measure of the rewarding/reinforcing properties of the drug. CPP has been found to occur with all known drugs of abuse (Tzschentke, 1998; Lynch et al., 2010).

Despite the possibility that khat use could lead to dependence and addiction, no preclinical studies have been done to show if khat has rewarding/reinforcing properties found with other drugs of abuse. Therefore, in this study, we assessed the rewarding/ reinforcing property of khat using CPP, a technically simpler and less expensive method than drug self-administration in determining the rewarding/reinforcing property of substance.

Materials and methodsMice (4 groups, n = 5) were tested in 3 chamber conditioned place preference (CPP) apparatus. In the pre-conditioning phase mice were given 20 min free access to all 3 chambers for 2 days to determine their chamber preference. For conditioning phase, on day 1, all mice were given saline injection (i.p.) and confined to their preferred chamber for 60 min. On day 2, control mice were given saline and other 3 groups were injected with methanolic extract of khat (i.p.) 1, 3, 9 mg/kg, respectively, and confined to their non-preferred chamber for 60 mins. This treatment was alternated for 8 days. In post-conditioning phase, day 11, the mice were once again allowed 20 min free access to all 3 chambers and their chamber preference measured. The time spent in the non-preferred chamber pre- and post-conditioning was analyzed with a paired t-test, and weight and pre-conditioning chamber preference with repeated measure ANOVA.

AcknowledgmentsThe staff of the Animal House, Department of Medical Physiology, University of Nairobi, and Department of Biochemistry for assistance in the preparation of the khat extract.This file from http://colinpurrington.com/tips/academic/posterdesign..

Results

Comparison between the pre- and post-conditioning times in the khat-paired chamber showed that 9 mg/kg khat extract treatment produced a significant place preference (t = 2.87; P = 0.045), while mice treated with 3 mg/kg khat extract showed increased time in the khat-paired chamber but there was no significant at that dose or the 1 mg/kg.

There was no significant difference in pre-conditioning time between the groups in the khat-paired chamber, as tested by one-way ANOVA (F4, 20 = 0.52; P = 0.73) showing that exposure during training of the mice to the distinctive environments did not influence their chamber preference. There was also no significant difference in weight between the groups at the start or over the course of the of the experiment as analyzed by 2-way repeated ANOVA (F (6,24) = 0.83; p = 0.56).

DiscussionThe present study was undertaken to evaluate the rewarding/reinforcing potential of fresh khat using the conditioned place preference test. The results show that after conditioning with fresh khat, mice showed preference for the khat-paired chamber.

While cathinone, the main psychostimulatory molecule in khat, has been shown to produce place preference in rats, the results of this study show that khat with its cocktail of alkaloids which include cathine (1S, 2S – (+) – norpseudoephedrine) and norephedrine as well as 62 different cathedulins, also produces place preference and therefore khat could produce dependence and addiction in the users as seem with other psychostimulants.

The results support studies in humans which found khat users meet the DSM – IV substance dependence syndrome criteria (Patel, 2015).

Leonard Kilekwang and Nilesh B. PatelDepartment of Medical Physiology, School of Medicine, University of Nairobi, P. O. Box 30197-00100, Nairobi, Kenya. Email:

npatel@uonbi.ac.ke.

Literaturecited• Lynch, W.J., Nicholson, K.L., Dance ME, Morgan, R.W., Foley, P.L.

2010. Animal Models of Substance Abuse and Addiction: Implications for Science, Animal Welfare, and Society Comparative Medicine.60(3):177-188.

• Nutt, D., King, L.A., Saulsbury, C., Blakemore, C. 2007. Development of a rational scale to assess the harm of drugs of potential misuse. Lancet. 369 (9566), 1047–53.

• Tzschentke, T. M. 2007. Measuring reward with the conditioned place preference (CPP) paradigm: update of the last decade. Addict Biol. 12(3-4), 227-462.

• Patel, N. B. 2014. Neurobiology of Khat (Catha edulis Forsk). M. Bentivoglio, E.A. Cavalheiro, K. Kristensson, N.B. Patel (eds.), Neglected Tropical Diseases and Conditions of the Nervous System. Springer New York. pp 307 – 319.

• WHO, 2008. Bulletin of the World Health Organization 86 (10).

Catha edulis Forsk (khat) induces conditioned place preference in mice

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Countries where khat is used and percentage prevalence of use

Photographs showing (A) bundle of khat, (B) the leaves and bark of the twig which are chewed, and (C) new variant of the Catha edulis – muguka – gaining popularity

Time spent in khat-paired chamber before and after conditioning with methanolic extract of fresh khat