Grooming, scratching and feeding : role of response competition in acute anorectic response to rimonabant in male rats

• Published in: Psychopharmacologia 2007-11, Vol.195 (1), p.27-39
• Main Authors: TALLETT, A. J, BLUNDELL, J. E, RODGERS, R. J
• Format: Article
• Language: English
• Subjects: Adult and adolescent clinical studies; Animal behavior; Animals; Anorexia - chemically induced; Anorexia - physiopathology; Anorexia - psychology; Anorexia nervosa; Antagonist drugs; Appetite; Biological and medical sciences; Body weight gain; Cannabinoid CB1 receptors; Competition; Data Interpretation, Statistical; Diet; Dosage; Dose-Response Relationship, Drug; Eating - drug effects; Eating - physiology; Eating - psychology; Eating behavior disorders; Experimental psychology; Feeding behavior; Feeding Behavior - drug effects; Feeding Behavior - physiology; Feeding Behavior - psychology; Food intake; Grooming; Grooming - drug effects; Grooming - physiology; Habituation, Psychophysiologic - drug effects; Injections, Intraperitoneal; Inverse agonists; Locomotion; Male; Medical sciences; Pharmacology; Piperidines - administration & dosage; Piperidines - toxicity; Pruritus - etiology; Pruritus - psychology; Psychology. Psychoanalysis. Psychiatry; Psychopathology. Psychiatry; Pyrazoles - administration & dosage; Pyrazoles - toxicity; Rats; Receptor, Cannabinoid, CB1 - antagonists & inhibitors; Rest - physiology; Rest - psychology; Rimonabant; Rodents; Satiety Response - drug effects; Satiety Response - physiology; Time Factors; Videotape Recording - methods; Weight Gain - drug effects; Weight Gain - physiology
• ISSN: 0033-3158; 1432-2072
• DOI: 10.1007/s00213-007-0880-2

Although the CB1 receptor antagonist/inverse agonist rimonabant acutely suppresses food intake in rodents, the behavioural specificity of this effect remains unclear. To profile the behavioural effects of rimonabant in a free-feeding context. Videoanalysis was employed to characterise the effects of acute rimonabant (1.5 and 3.0 mg/kg, IP) on the behaviour of non-deprived male rats exposed to palatable mash. Data were also collected on post-treatment weight gain, and, as prolonged appetite suppression has been found after single dosing with compounds of this series, rats were reassessed (drug-free) for food intake 7 days after initial testing. Both doses of rimonabant not only decreased mash consumption (44-55%) but also reduced 24-h weight gain. Although videoanalysis confirmed the inhibitory effects of rimonabant on feeding behaviour, it also revealed concurrent reductions in locomotion, rearing and sniffing as well as substantial (up to tenfold) and dose-dependent increases in grooming and scratching. Timecourse analyses further revealed that rimonabant dose-dependently induced frequent episodes of atypical scratching that waned over the test but which were succeeded by prolonged and behaviourally disruptive grooming. Finally, as groups did not differ in mash consumption on retest, any prolonged anorectic effect of acute rimonabant dissipates within 7 days of treatment. The anorectic response to rimonabant in male rats would appear to be due largely to response competition. This parsimonious conclusion is supported by the less profound (although still significant) increases in scratching and grooming observed in rats treated with a sub-anorectic dose (0.5 mg/kg) of the compound.