Evidence that spatial memory deficits following bilateral vestibular deafferentation in rats are probably permanent

• Published in: Neurobiology of learning and memory Vol. 94; no. 3; pp. 402 - 413
• Main Authors: Baek, Jean Ha, Zheng, Yiwen, Darlington, Cynthia L., Smith, Paul F.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.10.2010; Elsevier; Elsevier BV
• Subjects: Analysis of Variance; Animal memory; Animals; Behavior, Animal - drug effects; Behavior, Animal - physiology; Behavioral psychophysiology; Benzoxazines - pharmacology; Biological and medical sciences; Cannabinoid CB1 receptors; Cannabinoid drugs; Cannabinoids - pharmacology; Exploratory Behavior - drug effects; Exploratory Behavior - physiology; Fundamental and applied biological sciences. Psychology; Hippocampus; Male; Medical sciences; Memory Disorders - physiopathology; Morpholines - pharmacology; Naphthalenes - pharmacology; Nervous system (semeiology, syndromes); Nervous system as a whole; Neurobiology; Neurology; Piperidines - pharmacology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Pyrazoles - pharmacology; Random Allocation; Rats; Rats, Wistar; Rodents; Sensory perception; Space Perception - drug effects; Space Perception - physiology; Spatial Behavior - drug effects; Spatial Behavior - physiology; Spatial memory; Vestibular lesions; Vestibular system; Vestibule, Labyrinth - injuries; Cannabinoid drugs; Vestibular system; Hippocampus; Vestibular lesions; Spatial memory; Memory disorder; Nervous system diseases; Cognitive disorder; Rat; Internal ear disease; Rodentia; Central nervous system; Bilateral; Cannabinoid; Inner ear; Organ of hearing; Encephalon; Vertebrata; Mammalia; Animal; ENT disease; Vestibular syndrome; Deafferentation
• ISSN: 1074-7427; 1095-9564
• DOI: 10.1016/j.nlm.2010.08.007

► At 14months after bilateral vestibular loss, rats showed spatial memory deficits. ► These were present in light and darkness. ► They were more severe than at 5–7months post-op. ► Cannabinoid drugs had complex and dose-dependent effects on them. Previous studies of rats with bilateral vestibular deafferentation (BVD) have demonstrated spatial memory deficits, suggesting adverse effects on the hippocampus. However, the longest post-operative time interval that has been studied was approx. 5–7months post-surgery. In this study, we investigated whether rats exhibited spatial memory deficits at 14months following BVD and whether these deficits could be exacerbated by administration of cannabinoid (CB) drugs. Twenty-eight adult rats were divided into four groups: (1) sham surgery+vehicle; (2) sham surgery+the CB1/CB2 receptor agonist WIN55,212-2 (‘WIN’); (3) BVD+vehicle; and (4) BVD+WIN. WIN (1.0 or 2.0mg/kg/day) or vehicle, was administered (s.c.) on days 1–10 and 11–20 (respectively), 30min before the rats performed in a foraging task. On day 21, the CB receptor inverse agonist, AM251 (3.0mg/kg, s.c.), was administered before WIN or vehicle. To our surprise, BVD animals were impaired in using the visual cues during the probe test in light. In the dark trials, when visual cues were unavailable, BVD animals were unable to use self-movement cues in homing. However, WIN at 2mg/kg, significantly improved BVD animals’ homing time and number of errors in the dark through strategies other than the improvement in using self-movement cues. Furthermore, AM251 significantly improved heading angle in vehicle-treated animals and the first home choice in WIN-treated animals. These results suggest that at 14months post-BVD, the animals are not only impaired in path integration, but also piloting and that the spatial memory deficits may be permanent. The involvement of the cannabinoid system is more complicated than expected.