1521-0103/357/1/125–133$25.00 http://dx.doi.org/10.1124/jpet.115.228189 THE JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS J Pharmacol Exp Ther 357:125–133, April 2016 Copyright ª 2016 by The American Society for Pharmacology and Experimental Therapeutics Comparisons of D9-Tetrahydrocannabinol and Anandamide on a Battery of Cognition-Related Behavior in Nonhuman Primates Brian D. Kangas, Michael Z. Leonard, Vidyanand G. Shukla, Shakiru O. Alapafuja, Spyros P. Nikas, Alexandros Makriyannis, and Jack Bergman Department of Psychiatry, Harvard Medical School, Boston, Massachusetts (B.D.K., J.B.); Preclinical Pharmacology Laboratory, McLean Hospital, Belmont, Massachusetts (B.D.K., M.Z.L., J.B.); and Center for Drug Discovery, Northeastern University, Boston, Massachusetts (V.G.S., S.O.A., S.P.N., A.M.) Received July 29, 2015; accepted January 27, 2016 Downloaded from ABSTRACT The primary psychoactive ingredient of marijuana, D9-tetrahydro- 1Hpyrazole-3-carboxamide] and the FAAH inhibitor URB597, cannabinol (D9-THC), has medicinal value but also produces respectively, also were examined. The results showed the unwanted deleterious effects on cognitive function, promoting following: 1) D9-THC produced dose-related impairments of the search for improved cannabinergic therapeutics. The present discrimination-based cognitive behavior with potency that studies used a battery of touchscreen procedures in squirrel varied across tasks (discriminative capability , learning , monkeys to compare the effects of different types of cannabinergic flexibility , short-term memory); 2) anandamide alone and jpet.aspetjournals.org drugs on several measures of performance including learning URB597 alone were without effect on all endpoints; 3) ananda- (repeated acquisition), cognitive flexibility (discrimination reversal), mide following URB597 pretreatment and methanandamide had short-term memory (delayed matching-to-sample), attention (psy- negligible effects on discriminative capability, learning, and chomotor vigilance), and motivation (progressive ratio). Drugs reversal, but following large doses affected delayed matching- studied included the cannabinoid agonist D9-THC, fatty acid to-sample performance in some subjects; 4) all drugs, except amide hydrolase (FAAH) inhibitor cyclohexylcarbamic acid 3- anandamide and URB597, disrupted attention; and 5) progres- carbamoylbiphenyl-3-yl ester (URB597), and endocannabinoid sive ratio breakpoints were generally unaffected by all drugs at ASPET Journals on March 14, 2016 anandamide and its stable synthetic analog methanandamide tested, suggesting little to no effect on motivation. Taken [(R)-(1)-arachidonyl-19-hydroxy-29-propylamide]. The effects of together, these data indicate that metabolically stable forms of D9-THC and anandamide after treatment with the cannabinoid anandamide may have lesser adverse effects on cognitive receptor type 1 inverse agonist/antagonist rimonabant [5-(4- functions than D9-THC, possibly offering a therapeutic advan- chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)- tage in clinical settings. Introduction antinausea and antiemetic agent (reviewed in Sharkey et al., 2014). While the full therapeutic value of D9-THC or other CB D9 1 The cannabinoid receptor type 1 (CB1) agonist -tetrahy- agonists is not yet understood, such cannabinergic effects are D9 drocannabinol ( -THC) is the primary psychoactive ingredi- of known benefit in the palliative care of anorectic patients ent in marijuana, the most commonly used illicit drug in undergoing chemotherapy or suffering debilitating conditions the United States. Recent surveys estimate approximately such as AIDS or Alzheimer’s disease (reviewed in Cridge and 20 million current (past month) users (Substance Abuse and Rosengren, 2013). Mental Health Services Administration; (http://www.samhsa. The apparent medicinal benefits of D9-THC have led to a gov/data/sites/default/files/NSDUHresultsPDFWHTML2013/ broadening interest in the clinical utility of drugs that target D9 Web/NSDUHresults2013.pdf). In addition, -THC has ap- the endocannabinoid system. However, in this regard D9-THC parent medicinal value and there appears to be growing also is generally acknowledged to produce some unwanted acceptance of its therapeutic, as well as recreational, use. effects in humans. These include adverse effects on several D9 For example, -THC, formulated as Marinol for oral delivery, types of cognitive function and, especially, behavior thought to is employed as an appetite stimulant and can serve as an be mediated in the prefrontal cortex (reversal learning and attention) and hippocampus (short-term memory) (reviewed in Iversen 2005; Egerton et al., 2006; Crean et al., 2011; This research was supported by the National Institutes of Health National Zanettini et al., 2011). Laboratory studies with nonhuman Institute on Drug Abuse [Grants K01-DA035974 (to B.D.K.) and R01- D9 DA031020 (to J.B.)] primates comparing the relative impact of -THC across dx.doi.org/10.1124/jpet.115.228189. several cognitive endpoints have confirmed that these aspects 9 9 ABBREVIATIONS: CB1, cannabinoid receptor type 1; D -THC, D -tetrahydrocannabinol; DMTS, delayed matching-to-sample; FAAH, fatty acid amide hydrolase; FR, fixed ratio; ITI, intertrial interval; methanandamide (AM356), (R)-(1)-arachidonyl-19-hydroxy-29-propylamide; rimonabant (SR141716A), 5-(4-chlorophenyl)-1-(2,4-dichloro-phenyl)-4-methyl-N-(piperidin-1-yl)-1Hpyrazole-3-carboxamide; SEM, standard error of the mean; URB597, cyclohexylcarbamic acid 3-carbamoylbiphenyl-3-yl ester. 125 126 Kangas et al. of cognitive function appear particularly vulnerable to the chamber’s front wall (34  27 cm). An infusion pump (PHM-100- D9-THC (e.g., Schulze et al., 1988; Winsauer et al., 1999; 10, Med Associates, St. Albans, VT) outside the enclosure was used to Taffe, 2012; Wright et al., 2013). deliver pulses of 0.15 ml of a 30% sweetened condensed milk solution Concern regarding such adverse effects of D9-THC on cogni- into the shallow reservoir (diameter: 2.5 cm) of a custom-designed   tive function has led to efforts to develop cannabinergic drugs Plexiglas receptacle (5 3.5 1.27 cm). Both touchscreen and fluid reservoir were easily accessible to the subject. A speaker bar that retain medicinal value, yet produce lesser adverse effects (NQ576AT, Hewlett-Packard, Palo Alto, CA) mounted above the on cognition. One recent approach that has yielded encourag- touchscreen (i.e., at the top of the inside wall of the enclosure) was ing preclinical results does not target the development of novel used to emit an audible feedback click each time the subject touched a CB1 agonists but instead involves enhancing endogenous stimulus presented on the screen. All experimental events and data cannabinergic activity by pharmacologically inhibiting the collection were programmed in E-Prime Professional 2.0 (Psychology rapid metabolism of anandamide by fatty acid amide hydrolase Software Tools, Inc., Sharpsburg, PA). During all behavioral proce- (FAAH) (e.g., Kathuria et al., 2003; Seierstad and Breitenbucher, dures described subsequently, subjects were placed within the 2008; Gaetani et al., 2009; Pertwee, 2014). An emerging experimental chamber prior to the daily session and were not literature in which this approach is explored provides some restrained or restricted in their movement. preclinical evidence of efficacy in animal models of nausea, vomiting, and appetite (e.g., Williams and Kirkham, 1999; Procedures Cross-Mellor et al., 2007; Rock et al., 2008; Parker et al., 2009; Repeated Acquisition. Previously established methods were used Limebeer et al., 2014). However, the effects of anandamide on to train subjects to repeatedly discriminate novel visual discriminations Downloaded from cognitive function in nonhuman primates have not yet been (Kangas and Bergman, 2014). Briefly, each session began with concur- fully delineated, and consequently it is unclear whether rent presentation of two 7  7 cm digital photographs, each in a different anandamide (or other endocannabinoids) offer a therapeutic randomly selected quadrant of the screen (white background). A touch 9 advantage over CB1 agonists such as D -THC. The present response on one stimulus initiated the delivery of milk into the reservoir 1 studies were conducted to address this by examining the (S ) paired with an 880-millisecond yellow screen flash, and followed by relative impact of the cannabinoid agonist D9-THC and both a 10- second intertrial interval (ITI) blackout; a touch response to the 2 jpet.aspetjournals.org the endocannabinoid anandamide (administered alone and other stimulus immediately initiated the 10-second ITI (S ). The same following FAAH inhibition) and its metabolically stable two stimuli were presented during each of 200 trials comprising the day’ssession,andanewS1/S2 pair was introduced each session. analog methanandamide [(R)-(1)-arachidonyl-19-hydroxy-29- Photographs for each session were randomly selected from our labora- propylamide] on performance across a range of touchscreen- tory bank of .10,000 images. Thus, the subject was required to learn a based assays of cognitive function in nonhuman primates. new S1/S2 discrimination each session based on distinguishing features of two visual stimuli that had not been previously viewed (i.e., repeated acquisition). Subjects were exposed to the repeated acquisition task for Materials and Methods at ASPET Journals on March 14, 2016 30 sessions prior to introduction of the discrimination