Original article 191 Disruptive effects of the prototypical cannabinoid D9-tetrahydrocannabinol and the fatty acid amide inhibitor URB-597 on go/no-go auditory discrimination performance and olfactory reversal learning in rats Ljiljana Sokolica, Leonora E. Longd, Glenn E. Huntc, Jonathon C. Arnoldb and Iain S. McGregora The effects of D9-tetrahydrocannabinol (D9-THC; 0.3, 1, disrupting acquisition of the original discrimination. 9 3 and 10 mg/kg), and the fatty acid amide hydrolysis Rimonabant (CB1 antagonist; 3 mg/kg) reversed all D -THC inhibitor URB-597 (0.1 and 0.3 mg/kg), on auditory and and URB-597 effects on auditory discriminations and olfactory go/no-go discrimination tasks were examined in olfactory discrimination reversals. These results confirm rats. The aims were to assess (i) whether simple olfactory impairment of cognitive flexibility (reversal learning) and auditory discrimination tasks are sensitive to by cannabinoids and show remarkable sensitivity of cannabinoid interference and (ii) whether manipulation of auditory discrimination performance to D9-THC and endogenous cannabinoid levels with URB-597 might have the augmented endocannabinoid signalling produced by adverse effects on perceptual and cognitive functions. URB-597. Behavioural Pharmacology 22:191–202 c 2011 Thirsty rats were trained to nose poke at a ‘sniff port’, Wolters Kluwer Health | Lippincott Williams & Wilkins. where odours were briefly presented. After one odour Behavioural Pharmacology 2011, 22:191–202 (S + , lemon), licks made at an adjacent tube were 9 rewarded with water, whereas licks after a second odour Keywords: D -tetrahydrocannabinol, auditory learning, cannabinoid, fatty acid amide hydrolase inhibition, olfactory learning, rat, URB-597 (S – , strawberry) were unrewarded. In an analogous aSchool of Psychology, bDepartment of Pharmacology, cDiscipline of Psychiatry, auditory task, nose pokes produced an auditory S + d 9 Concord Centre for Mental Health, University of Sydney and Neuroscience (beep) or S – (white noise). D -THC and URB-597 impaired Research Australia, New South Wales, Australia performance on the auditory but not the olfactory Correspondence to Iain S. McGregor, PhD, School of Psychology, University discrimination task. Auditory performance was still affected of Sydney, A 18, Sydney 2006, Australia on the day after D9-THC (3 and 10 mg/kg) and URB-597 E-mail: [email protected] 9 (0.3 mg/kg) exposure. D -THC and URB-597 markedly Received 17 October 2010 Accepted as revised 18 December 2010 impaired olfactory discrimination reversals without Introduction associative significance (Robbe et al., 2006; Deadwyler et al., Cannabis is the most widely used illicit drug in the world 2007; Hajos et al., 2008; Robbe and Buzsaki, 2009). and has well-documented sedative, analgesic, appetite- stimulatory and psychedelic effects, thought to be due to Many anecdotal reports suggest that cannabis affects its major psychoactive component, D9-tetrahydrocanna- auditory perception in humans, with an increased binol (D9-THC) (Ashton, 2001; Iversen, 2003, 2005; appreciation of auditory, particularly musical, stimuli Howlett et al., 2004; El-Alfy et al., 2010; Robinson et al., during acute intoxication (Fachner, 2006). A small 2010). Acute and chronic exposure to D9-THC has been number of laboratory studies have explored cannabinoid shown to impair cognitive function, with broadly similar effects on tasks involving the auditory modality. Canna- effects reported in humans and laboratory subjects binoids have been shown to cause hyper-reactivity in (Egerton et al., 2006; Ranganathan and D’Souza, 2006; mice to unexpected, loud auditory stimuli (Holtzman Solowij and Battisti, 2008; D’Souza et al., 2009; Sofuoglu et al., 1969; Boggan et al., 1973). In humans, an impair- et al., 2010). Characteristic effects in rodents include im- ment of auditory signal detection was observed in pairment of spatial learning, working memory and atten- subjects intoxicated with cannabis (Moskowitz, 1974). tional processes (Mallet and Beninger, 1998; Presburger Chronic cannabis use is associated with an impaired and Robinson, 1999; Hampson and Deadwyler, 2000; ability to filter out irrelevant auditory stimuli in an Verrico et al., 2004; Silva de Melo et al., 2005; Robinson oddball task and the use of different strategies of et al., 2007; Varvel et al., 2007; Boucher et al., 2009, 2011). attention allocation in auditory information processing Such effects may reflect cannabinoid-mediated disruption tasks (Solowij et al., 1995; Kempel et al., 2003). Smoking of cortical and hippocampal electrical activity, which marijuana also produced changes in brain metabolism or underlie the encoding of stimulus features and their regional cerebral blood flow in auditory cortices during a 0955-8810 c 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins DOI: 10.1097/FBP.0b013e328345c82b Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. 192 Behavioural Pharmacology 2011, Vol 22 No 3 focused attention task (O’Leary et al., 2000, 2002). ability when contingencies were reversed (Egerton et al., Cannabinoid disruption of sensorimotor gating to auditory 2005). This was interpreted as general impairment in stimuli has also been recently reported in the prepulse cognitive flexibility linked to disruptive effects of D9- inhibition of startle paradigm in rats and mice (Schneider THC on prefrontal and orbitofrontal functions (Egerton and Koch, 2002; Malone and Taylor, 2006; Boucher et al., et al., 2005; Roser et al., 2010). 2007, 2011) and human cannabis users (Kedzior and Martin-Iverson, 2006), and this has been linked to We have developed a task that allows drug effects on both cannabinoid-induced changes in auditory stimulus- auditory and olfactory discriminations to be assessed evoked electrophysiological activity (Hajos et al., 2008). (Sokolic and McGregor, 2007). In this go/no-go discrimi- In contrast, cannabinoid effects on olfactory perception nation paradigm, rats nose poke to receive either auditory are relatively uncharacterized. The appetite-stimulatory or olfactory stimuli of brief duration that signal either the effects of cannabinoid might reflect an increased availability (S +) or nonavailability (S –) of a water reward pleasurable sensory experience of foodstuffs (Yoshida at an adjacent lick tube (Fig. 1a). Using this task, we et al., 2010), presumably through an interaction with found that benzodiazepines selectively impair the hedonic processes related to gustation and olfaction acquisition and reversal of olfactory, but not auditory (Mahler et al., 2007). With respect to olfactory learning, discriminations (Sokolic and McGregor, 2007). As the rats engaged in a foraging task in which odours cued the auditory and olfactory discrimination tasks have identical location of food rewards showed normal performance motor, motivational, and response-inhibition require- when tested with D9-THC (THC Pharm GmbH, ments, modality-specific impairment caused by drugs Frankfurt Main, Germany) but showed an impaired can be readily uncovered using this paradigm. Fig. 1 (a) Auditory stimuli (Apparatus) Beeper (S + ) vs. Noise (S – ) Sniff port (nose poke here for stimuli) Auditory condition Olfactory condition Lick port (lick here for water delivery on S + trials) Olfactory stimuli Lemon vs. Strawberry (S+) (S–) (b) (c) 50 50 ∗∗∗ (Auditory) ∗∗ (Olfactory) 40 40 30 30 ∗∗ 20 ∗ 20 Errors to criterion 10 10 0 0 - - - - - - le 1 3 le - 1 - 3 ic 0.3 ic 0.3 h h Ve Ve rimonabant + C TH THC Rimonabant (a) The olfactometer apparatus in which olfactory and auditory go/no-go discriminations and discrimination reversals were tested. (b) D9- tetrahydrocannabinol (D9-THC) impairs the performance of a well-learned auditory discrimination task. Impairment was also seen 24 h after administration of D9-THC (3 mg/kg). Asterisks represent a significant within-subjects drug effect relative to previous baseline performance (*P < 0.05, **P < 0.01, ***P < 0.001). Rimonabant had no significant effect on the performance of the auditory group. (c) Effects of D9-THC and rimonabant on the performance of a well-learned olfactory task. There were no significant drug effects on olfactory discrimination performance. Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited. Cannabinoids disrupt auditory discrimination Sokolic et al. 193 In this study, our primary aim was to assess the effects Apparatus of the prototypical cannabinoid D9-THC on auditory All testing occurred in 12-channel air-dilution olfacto- and olfactory go/no-go discriminations, and to evaluate meters (Fig. 1a) using methods similar to those described whether any general performance impairments, or any by Slotnick (2001) and Slotnick and Schellinck (2001). modality-specific effects, were evident. On the basis of Two of the four olfactometers were modified so that they the existing literature, we predicted that cannabinoid could also be used for auditory discrimination tasks might interfere with auditory discrimination ability and (Sokolic and McGregor, 2007). The test chamber for each with the ability to reverse previously learned discrimina- of the four units was a 17 cm (W) Â 24 cm (L) Â 25 cm tions. This study also focused on the fatty acid amide (H) Plexiglas box fitted with a stainless steel grid floor. A hydrolase (FAAH) inhibitor URB-597. This drug in- brushless ventilation fan was mounted on one side of the creases brain anandamide levels