Place preference for the psychostimulant cathinone is blocked by pretreatment with a dopamine release inhibitor

Prq. Ptited

NeumPsychopharmacuL in Great

Brltaln.

B BbL Psychtat

All rt&ts

1993.

0278

Vol. 17. pp. 637-649

o 1993

reserved

- 5846/93 Pergamon

$24.00 Press

PLACE PREFERENCE FOR THE PSYCHOSTIMULANT CATHINONE IS BLOCKED BY PRETREATMENT WITH A DOPAMINE RELEASE INHIBITOR

DANIEL J. CALCAGNE’ITI and MARTIN D. SCHECHTER Department of Pharmacology Northeastern Ohio Universities College of Medicine Rootstown, OH, U.S.A.

(Final form, May 1992)

Abstract Calcagnetti, Daniel J. and Martin D. Schechter: Place Preference for the Psychostimulant Cathinone is Blocked by Pretreatment with a Dopamine Release Inhibitor. Prog. Nemo-psychopharmacol. & Biol. Psychiat. 1993, 17(4): 637-649. The objective of Exp. 1 was to determine whether intmcerebroventricular (XV) injection of cathinone CATH (8.0-32 pg) would produce a dose-dependent conditioned place preference (CPP) and/or activation in rats. Results indicate that tats conditioned with 16 or 32 pg doses of CATH significantly increased the time spent in their less preferred side, whereas rats conditioned with the 8.0 pg dose failed to show any shift from baseline preference. The 16 and 32 pg doses of CATH also significantly @< .004) increased activity by more than 65% of baseline. Exp. 2 was designed to determine whether ICV pretreatment with a dopamine release inhibitor CGS 10746B (CGS; 15 pg/mt) would block place conditioning produced by CATH. The results demonstrate that CGS pretreatment effectively blocked CATH-induced place conditioning and the CATH-induced elevation of activity. Kevwords: activity, cathiuone, intracerebroventricular, reward.

CGS

10746B,

conditioned

place

preference,

dopamine,

Abbreviations: cathinone (CATH), CGS 10746B (CGS), conditioned place preference (CPP), intracerebroventricular (RX).

Introduction Cathinone (CATH) is the naturally-occurring

psychoactive constituent found in the leaves of the

Khat shrub (CWzeu edulis Forsk, family Celmtraceae). This plant is cultivated in eastern Africa and southern Arabia by locals who gather in social settings to chew the leaves and experience effects that are practically indistinguishable from those produced by amphetamine. 637

These include talkativeness,

Ltd

638

D. J. Calcagnetti and M. D. Schechter

hyperactivity, anorexia, increased alertness and euphoria (Kalix, 1980). Animal experiments have also shown the similarities between the neurochemical mechanisms of action of amphetamine and CATH in that they both attenuate the firing of dopaminergic neurons (IvIereu et al. 1982), increase the release of dopamine (Kalix et al. 1986; Kalix et al. 1987; Kalix and Glennon, 1986; Pehek et al. 1990; Zelger and Carlini, 1981) and, at high doses, block the reuptake (Wagner et al. 1982) of dopamine (Kalix, 1990). Additionally, both psychostimulants are able to condition a preference for place (Hoffman, 1989; Schechter, 1991). Historically, the present form of the conditioned place preference (CPP)-test was first developed to measure the positive affect of drugs of abuse (Rossi and Reid, 1976). In fact, the term “hedonomica” has been coined to label technologies, such as CPP-testing, designed to measure positive affect (Reid et al. 1989). CPP-testing has now become an increasingly used paradigm to screen drugs for their abuse potential and in addition, conditioned place testing has the advantage of also assessing the aversive properties of drugs (Carr et al. 1989; Hoffman, 1989; Swerdlow et al. 1989). CPP has also been used to characterize the rewarding effects of non-drug behaviors, such as access to a sexually receptive mate (Hughes et al. 1990) and juvenile play (Calcagnetti and Schechter, 1992). We use the term “reward”, rather than reinforcement to characterize the shii in time spent by subjects once conditioned with drug as approach behavior (Schneirla, 1959) especially since no contingency is set between the drug delivery and exposure to the cues of the drug-paired apparatus.

The reasoning in

support of this position is discussed elsewhere (Beninger et al. 1989; Calcagnetti and Schechter, 1992; Wise, 1989).

The shift in the amount of time spent in the drug-associated chamber following

conditioning is called a “preference” although this term is a misnomer on the basis of absolute psychophysical measurements.

However, the term “preference” is used here based on the de facto use

of this term in the CPP literature. Recently,

CATII

(0.4-l .6 mg/kg) was shown to condition

a place preference

following

intraperitoneal administration in tats @Icehan and Schechter, in review). They also reported that the novel dopamine release inhibitor (Altar et al. 1986; Wood et al. 1988) CGS 10746B (CGS, 2.5 mg/kg) attenuated the CATH-induced CPP. The purpose of the first experiment was to extend these findings by employing the ICV route of CATH administration in order to determine whether a similar CPP could be produced following central administration.

At the conclusion of CPP testing, the activating

effects of CATH were also measured using the same doses tested in the CPP paradigm. The primary mechanism of CATH action appears to be release of presynaptic dopamine (Kalix, 1990) and the CPP produced by CATH may, therefore, be mediated by its influence on dopamine reward systems. A way to manipulate the dopaminergic component mediating a behavioral effect is to block dopamine release presynaptically and CGS is believed to decrease the pm-synaptic release of dopamine by mechanisms that neither block post-synaptic sites nor influence dopamine metabolism,

639

CGS 10746B blocks cathinone preference

such as might be seen with haloperidol or alpha-methyl-paratyrosine, discrimination

paradigm,

peripherally-administered

CGS (lo-30

respectively.

mg/kg)

attenuates

In a drug cathinone

discrimination (Schechter, 1990). Exp. 2, therefore, was conducted to test whether a pre-synaptic dopamine release inhibitor would similarly block the production of ICV CATH-induced

place

conditioning.

Animals In Bxp. l., experimentally-naive,

male rats (n=36) of Sprague-Dawley descent (175195 g),

purchased from Zivic-Miller Laboratories Inc. (Allison Park, PA) were individually housed in stainless steel hanging cages and allowed & libitum access to food (Purina 5008) and water. They were maintained in a colony room with a constant temperature and humidity on a 12: 12 hr lightdark cycle (dark onset at 18:00 hr). Conditioning and testing were conducted in a room separate from the colony room. In Exp 2., the surgery, drug injection, CPP conditioning/testing,

and activity procedures were

identical to those employed in Exp. 1. A separate group of experimentally-naive male rats (n=8) were used. All subjects were handled in compliance with the “Guide for the Care and Use of Laboratory Animals”, Dept. of Health, Education and Welfare Publication, 1985.

Sureerv. ICV Iniection and Drugs Rats (280-350 g) were anesthetized using 100 mg/kg of ketamine hydrochloride plus a 0.15 ml injection of xylazine (10 mg/ml, Sigma Chemical).

A stainless steel outer guide cannula (22 gauge;

Plastics One, Roanoke, VA) was stereotaxically implanted into the right lateral ventricle using the coordinates: 0.5 mm posterior to bregma, 1.5 mm lateral to midline, and 3.2 mm ventral to the surface of the dura, with the skull kept level between lambda and bregma (Paxinos and Watson, 1987). Subjects were given at least 7 days of post-surgical recovery prior to the start of conditioning. ICV injections were performed using a modified method as described by Myers (1971). Briefly, the drug solution was backloaded into a 28 gauge internal cammla via a length of PE-20 tubing affixed to a 25 pl Hamilton microsyringe. air bubble.

Microinjections were monitored by following the movement of an

The internal cannula extended 0.5 mm beyond the guide cannula.

Drug injections were

performed using a repeating dispenser (Hamilton, 83700) while gently holding the rats and were delivered at a constant rate of 1 4/5 sec. (-)Cathmone hydrochloride (NIDA) was dissolved in sterile 0.9 % saline. Saline also served as the

D. J. Calcagnetti and M. D. Schechter

640

vehicle (VEH) control injection. All doses tested (8.0, 16, and 32 cglrat) are expressed as the salt and were administered in a total injection volume of 5 pl. piperazinyl)-imidazol(22,

In Exp. 2., CGS 10746B [5-(Cmethyl-1

l-b) (1,3,5) benzothiadiazepine maleate](CIBA-GEIGY Corp., Summit, NJ)

was injected ICV 5 min prior to CATH (32 pglrat).

CGS (15 rg of the salt) was dissolved in sterile

0.9% saline and administered in an injection volume of 5 ~1. The dose of CGS was selected from previously published dose-response data wherein 15 pg failed to decrease locomotion significantly or alter baseline side preference in CPP testing (Calcagnetti and Schechter, 1991).

Apparatus and Procedure Place conditioning

and testing were conducted in one of four modular test component units

(Lafayette Inst. Co., Lafayette, IN) as previously described in detail (Calcagnetti and Schechter, 1991). Briefly, the right and left end sections of the three-chambered apparatus provided the following distinct discriminable cues: the “dark” side of each unit was illuminated by a 6W, 30V red light bulb and contained a smooth black plastic floor; the “light” side was illuminated with a 6W, 30V white light bulb and had a grid floor over a drop pan filed with pine wood shavings.

Location throughout the

chamber was detected by weight-sensitive microswitches such that entry into the chamber closed the switch. A computer automatically recorded the time (in set) spent in each section of the apparatus. This procedure conformed to the “biased” method of CPP-testing (Swerdlow, et. al. 1989). Validation of the biased CPP method was established by conducting a conditioning saline-saline control experiment.

Baseline side preference was accessed by allowing rats to freely roam throughout the 3

chambered apparatus.

Over the next 8 days, conditioning trials were conducted in which rats were

injected with saline on 4 days and confined to their nonpreferred side, whereas, on interspersed days, saline injections were paired with confinement in their preferred side. After the conditioning trials, rats were allowed free access to all chambers and preference was reassessed. A paired t-test showed that preconditioning preference did not significantly differ from post-conditioning preference (df=5; t=0.56; p= 0.6).

These data indicate that in the biased CPP testing procedure, baseline preference

does not diier from pre- to post-conditioning when conditioned with a saline control. Two days prior to the start of testing in the present manipulations, subjects were transported to the testing room where they remained for 4 hrs. Following habituation to transportation and handling, subjects underwent three treatment phases: 1) Assessment of baseline side preference (defmed as the majority of time each rat spent in either the “light” or “dark” side of the CPP apparatus), 2) drug conditioning and 3) place preference testing.

On the baseline day each subject was placed into the

middle gray chamber and allowed 15 min of free access to explore the entire CPP-test apparatus. This served to establish a “pre-conditioning baseline” of place preference per subject, i.e., the side that the

CGS 10746B blocks cathinone preference

641

rat spent the majority of time (in set) during the 900 set session was considered its preferred-side,

whereas the other side was its non-preferred side. In Exp. 1., drug-place conditioning was then initiated and conducted twice daily. In the morning session (1100 hrs) rats were injected ICV with VEH, immediately placed into their preferred side and confined there for 30 mm by insertion of sheet metal panels at the entrance.

During the afternoon

sessions (1300 hrs), rats were injected with their assigned ICV dose of CATH and immediately confined to their less-preferred side for the same 30 min duration.

Twenty-four hr following the 4th

(last) day of conditioning, place preference was again measured. Each subject was allowed free access, as on the baseline day, for 15 min in a non-drugged state. On the following day, subjects were again allowed free access in the place apparatus immediately after an ICV injection of their assigned dose of CATH. This design permitted comparison between the non-drugged and drugged-state performance of place preference testing and, thus, time of testing became a repeated factor (see statistics below). In Ekp. 2., during their morning conditioning sessions, rats received two ICV injections of VEH spaced 5 min apart prior to confinement in their preferred side. In the afternoon sessions, rats were pretreated with ICV administered CGS 5 mm prior to receiving a second ICV injection of CATH (32 pg/mt).

Following the administration

of CATH, the rats were immediately confined to their

less-preferred side of the CPP apparatus.

Eight photosensors, affixed four per side of a 45.5 X 35.5 X 20.5 cm Plexiglas cage, allowed for activity measurements.

The sensors were situated 5.5 cm above the floor and 9.5 cm apart along the

wall of the longer side. Photosensor interruption resulted in one activity count. Activity counts were recorded by a computer at 5 min intervals throughout the 30 min testing session. In Ekp. l., two hr after the conclusion of non-drug CPP testing, activity measurements were collected immediately after ICV administration of VEH. Two days after CPP testing with CATH, a final activity measurement was conducted for the 30 min immediately following the ICV administration of CATH. Pats remained in their assigned dose groups and, thus, received the same dose of CATH as they did during CPP conditioning.

In Ekp. 2., the procedure for activity measurements was identical except that a 5 min

pretreatment interval with CGS was also employed prior to ICV administered CATH (32 rg).

This procedure conforms to a non-counterbalanced drug regimen, i.e., all rats axe tested fit non-drug state and are re-tested the next day with the drug.

A non-counterbalanced

in the

design was

employed because the impact of testing 112 the rats with CATH immediately following conditioning may have acted as a confounding variable.

Several experiments using rats (Gugehnann et al. 1985;

642

D. J. Calcagnetti and M. D. Schechter

Kalix,

1980; Yanagita, 1979) have characterized peripherally administered doses (0.2525 mg/kg) of

CATH on activity. The maximally effective dose (10 mg/kg) resulted in an &fold increase in activity over baseline (Kalix, 1980). The ICV doses of CATH were selected from dose-response data wherein ICV administered CATH effectively increased activity (Calcagnetti and Schechter, in press).

Design. Measurements and Data Analvsis In Exp. I., side preference baseline tests indicated the time (see) each rat spent in its less-preferred side; these were ranked (from highest to lowest) and rats were assigned to one of three groups in blocks of three. The 12 groups of three rats were then assigned (from highest to lowest) to one of three dose groups. Matching the baselines over dose groups in this manner served as a fixed factor to equate the groups for side preference rather than random assignment and constituted a split-plot experimental design (Kirk, 1968).

As the histological placement of three subjects, each from a

different assignment group, was not positively confirmed, their data, as well as the data from their entire block (total n=9),

were excluded from statistical analysis and results.

This final analysis,

consisted of 27 subjects from nine assignment groups. The critical measurement was the actual time (in see) that the subjects spent in the less-preferred side of the apparatus during CPP testing without and, then on the following day, with CATH administration, each compared to their baseline. As there were three levels of assignment groups, three levels of dose and three repeated measures on testing times (CPP baseline, post-conditioning without drug and post-conditioning with drug), this experiment conformed to a three factor (Assignment groups X Dose X Testing times) split-plot design. Thus, a three factor analysis of variance (ANOVA) with repeated measures on the time of testing was performed using measurements of the set spent in the less-preferred side. Since the factor associated with Assignment groups failed to be a reliable source of variance by itself, or to interact with other factors @s > 0.3), it was subsequently dropped from the analysis and these dam are described by a two factor repeated measures ANOVA design. Where appropriate, data sets are compared by Scheffe’s test (Kirk, 1968) or paired t-tests. Measurements for baseline activity between groups were analyzed by one-factor ANOVA and, where appropriate, followed by unpaired f-tests. As rats in Exp. 2. were randomly assigned to this group and baseline matching was not employed, CPP data was analyzed by a simple repeated measures ANOVA (Howell, 1987) and activity data were analyzed by a paired I-test. The alpha level for analyses was set at 0.05.

Testine of Cannula Patencv and Histoloeical Verification of Placement To test cannula patency behaviorally, subjects underwent post-surgical treatment with angiotensin

643

CGS 10746B blocks cathinone preference II (AGII), a potent dipsogen (Epstein et al. 1970), two days prior to the start of conditioning.

Cannula

patency was confirmed by measuring water intake following ICV AGII administration (40 ng /5 ~1). Rats that failed to drink at least 5 ml of water 15 min after AGII administration were excluded from subsequent testing. At the conclusion of CPPlactivity testing, subjects underwent a second dipsogenic measurement with AGII to re-co&m

cannula patency.

After the second AGII test, all subjects underwent histological verification of cannula placements. Subjects were overdosed with sodium pentobarbital(200 mg/kg) and injected ICV with 4 pl of Staedtler (#C745) ink. Approximately 10 min after injection of the ink, each subject was perfused transcardially with physiological (0.9%) saline followed by a solution of buffered formalin (10%). Their brains were rapidly removed and stored in formalin for 24 hr. Coronal brain sections were made along the cannula tract.

Positive cannula placement was defined by the presence of ink throughout the ventricles.

Placement for subjects was visually verified in all but three subjects.

Results

In Exp. l., the time (set) that rats, in each of the three CATH dose groups, spent in the less-preferred side of the CPP apparatus was analyzed by a two-factor ANOVA (Dose X Testing Days) with the days of CPP testing being the repeated measure. These results are graphed in Figure 1. The main effects of dose F(2,27)=35.3,

and testing days, F(2,48)=49.6,

yielded

significant differences, es’ < .OOl. The interaction was also significant, F(4,48)=11.0,

p < 001.

Comparison by Scheffe’ test of the time spent in the less-preferred side between dose groups on the CPP test day without drug and the CPP test day with drug revealed that postconditioning with either the 16 or 32 pg doses of CATH significantly (Fs> 17.5; ps< .Ol) increased (by 81.7-122.32)

time

spent on the less-preferred side in comparison to the 8.0 pg dose. Comparison of the CPP baseline scores did not reveal reliable differences between the three doses, Fs < .2; ps >05.

Scheffe’ test

comparisons of CPP scores between the 16 and 32 pg dose groups across test days did not differ, Fs < 1.1; ps >.Ol. Scheffe’ comparisons of CPP scores within each dose, across repeated CPP testing, revealed that following conditioning the 16 and 32 pg dose scores of the CPP test day with and without drug were significantly (Fs > 14.4; ps < .Ol) increased (81.7-115.8%) over baseline. Scheffe’ test comparisons of CPP baseline scores to CPP test day with and without drug at the 8.0 pg dose did not reliably differ, Fs < .2, ps > .05. The CPP scores from test day without drug and test day with drug did not diier for any dose level, Fs < 2.2, ps > .Ol.

Thus, conditioning with 16 and 32 pg doses of CATH

consistently resulted in rats spending more time on the less-preferred side regardless of whether the rats

D. J. Calcagnetti and M. D. Schechter

0

BASELINE

q

TEST-NO DRUQ

q

TEST+CATH

600

600

400

300

206

100

0 6.0

3;

16

ICV

CATHINONE

CATH

3&S

16

(pglrat)

Fig. 1. Mean (and standard error of the mean) set spent in the less-preferred side of the place conditioning apparatus during baseline and after post-conditioning in the non-drug (TEST-NO DRUG) and with ICV administered cathinone (TEST+CATH) for three dose groups (8.0, 16 and 32 pglrat). For comparative purposes, the last three bars on the far right show the baseline place preference and post-conditioning impact of pretreatment with CGS (15 pg) followed in 5 min with an ICV injection of CATI-I (32 pg) and are labeled “CATH 32+CGS 15”. An asterisk indicates significant (p < 0.01) differences from baseline using Scheffe’s test.

were tested in the drug-free state or just following ICV injection of CATH. The critical measurements for activity were the number of photosensor interruptions on two days of 30 mm testing sessions following ICV injection of VEH or CATH (Treatment) in rats assigned to one of three dose levels of CATH (8.0, 16 and 32 pg/rat).

The results are shown in Fig. 2.

One-factor ANOVA of baseline activity scores did not reveal significant dose group differences, F(1,26)= .Ol; p=.99. group.

Thus, the baseline group scores were pooled and served as a single control

Drug day dose group data were compared to the control group by unpaired l-tests.

This

analysis revealed significant differences between the control group and the 16 pg, as well as the 32 pg, CATH dose (dfs=34; ts > 2.9; ps C .004). An unpaired l-test between the control group and the 8.0 pg dose of CATH did not reveal a reliable difference (df = 34; t = .3.9; P = .70).These results indicated that the 16 and 32 yg doses of CATH significantly increased activity compared to baseline by 73.8 and 68.256, respectively.

The 8.0 pg dose failed to affect activity.

CGS 10746B blocks cathinone preference

645

In Exp. 2., simple repeated measures ANOVA of the time spent on the less preferred side of the CPP apparatus (baseline, post-conditioning

without drug and post-conditioning

with drug) in rats

pretreated with ICV CGS+CATH did not reveal reliable differences, F(2,14)=.44,

p > 0.05. These

results indicated that pretreatment with CGS (15 pg) blocked the increase in the time spent in the less-preferred side that was observed previously after conditioning with the 32 pg dose of CATH administered alone. These data are shown on the far right side of Fig. 1 (labeled “CATH32+CGSl5”) for comparative purposes. VEH and CGS activity scores were compared using a paired l-test. The comparison did not reveal a statistically significant difference (df = 7; t = .25; p = .8 1). The mean ( f SEM) photocell interruptions for VEH and CGS+CATH treatments were 240 (51.9) and 252.7 (54.7), respectively.

Importantly,

these results also demonstrate that CGS (15 rg) did not significantly decrease activity scores compared to VEH injection.

This finding is in accord with previously reported results (Calcagnetti and

Schechter, 1991).

The present findings represent the ftrst use of the ICV route for administration of CATH to condition a preference for place. ICV administration of either 16 and 32 pg CATH, when paired with confinement in the less-preferred side of a CPP apparatus, significantly increases the time spent in that side.

In contrast, the 8.0 pg dose did not increase the pre-conditioning

baseline side preference.

Similar findings were observed in the measurement of activity in that the 8.0 pg dose of CATH failed to affect activity, whereas the 16 and 32 pg doses significantly increased activity.

Furthermore, the

production of an all-or-none CPP between the 8.0 and 16 pg doses of CATH is representative of a “step-up” function (i.e., no significant increase at the lower dose and a maximum increase with the next highest dose) that is frequently observed in CPP studies (Carr et al. 1989; Spymki et al. 1985). Although there was a trend indicative of dose-response between the 16 to 32 pg doses without drug, this difference was not statistically significant.

These data support the hypothesis that the ICV

administration of CATH produces interoceptive effects that result in an increase in the time spent in the less-preferred side of a CPP apparatus. A similar dose effect relationship was observed for CPP and activity (the 16 and 32 pg doses significantly increased activity 68-7496). It is tempting to speculate that increased activity may have played an important role in CPP as these effects are co-produced by CATH. (1988) have demonstrated that amphetamine-induced physically restrained.

However, Carr et al.

CPP occurs even when a rats’ activity is

In addition, even more recent studies of dopamine release in the nucleus

accumbens support the notion that dopamine plays a key role in stimulus reward that is not explained

646

D. J. Calcagnetti

and M. D. Schechter

ii CATHINONE

3’2

(pght)

Fig. 2. Mean (and standard error of the mean) photosensor interruptions (activity) during 30 mm testing sessions in rats given ICV saline vehicle (VEH) or cathinone (8.0, 16, and 32 rglrat). An asterisk indicates significant (p c 0.05) differences from baseline using unpaired I-tests.

by its role in arousal or locomotion.

Using in vivo microdialysis probes, one study has shown that

dopamine levels increase 37% in naive rats following an intraoral injection of saccharin, whereas rats conditioned to a saccharin taste aversion by saccharin plus LiCl pairings, showed a 40% decrease in dopamine release (Marks et al. 1991). These data serve as evidence that this putative rewarding taste stimulus results in dopamine release and that, following aversive conditioning, the same stimuli can produce a decrease in neural dopamine release. Since neurochemical studies have demonstrated that the major effect of CATH, like amphetamine, is to promote the pie-synaptic release of dopamine (Kalix, 1990; Kalix and Glennon,

1986), one

hypothesis is that CATH-induced dopamine release produces a state of positive affect whereby the environmental cues of a specific chamber of the CPP apparatus, via pairings, are approached and act as rewarding stimuli.

It would be of considerable interest to measure, via microdialysis, whether

dopamine release occurs in the nucleus accumbens following drug-free place testing when the rat is in the same chamber wherein a psychostimulatory drug was previously conditioned.

If this, indeed,

occurred it would serve as evidence for the hypothesis that the drug-paired environmental cues evoke neurochemical changes indicative of reward and operationally defined as approach.

647

CGS 10746B blocks cathmone preference

The results of Exp. 2. demonstrate that the ICV pretreatment with CGS completely blocked the increase in the time spent in the less-preferred side as should have been observed following the 32 pg CATH-paired conditioning sessions.

This blockade was evident regardless of whether preference

testing was conducted with or without the presence of drug. Importantly, the activity effects of CATH (32 pg) were also blocked by CGS.

These findings support the hypothesis that the psychomotor

stimulant effects of CATH are mediated, at least in part, by a dopaminergic mechanism since the inhibition of the release of dopamine prevented the expression of both CPP and activation.

In short,

dopamine release is, at least, one mechanism of action whereby CATH produces a positive affective state; a factor that may explain its abuse by humans. In addition, CGS may represent a research tool to c‘ plore both reward-related addictive and psychopathological, processes involving dopaminergic brain mechanisms.

Following the ICV administration of CATH in a cue-specific place, a significant increase in the time spent in that place was observed.

In addition, the ICV administration of CATH dose-dependently

increased activity in rats. Rats pretreated (RX; 15 pg) with the putative dopamine release inhibitor, CGS, and followed by a second ICV injection of CATH, did not show an increase in the drug-paired chamber nor did they increased activity.

Acknowledgements The authors are grateful to the National Institute of Drug Abuse for the supply of (-)cathinone and to Dr. Richard Lovell of the CIBA-GEIGY Corp., Summit, NJ, for the generous gift of CGS 10746B. We also thank Susanne M. Meehan and Timothy L. Gordon for their contribution regarding the statistical treatment of these data. This research was funded, in its entirety, by National Institute of Drug Abuse grant No.3591 to M.D.S.

D.J.C. was funded by the State of Ohio Academic Challenge

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