Cat odor, but not trimethylthiazoline (fox odor), activates accessory olfactory and defense-related brain regions in rats

• Published in: Neuroscience Vol. 151; no. 4; pp. 937 - 947
• Main Authors: Staples, L.G, McGregor, I.S, Apfelbach, R, Hunt, G.E
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 19.02.2008; Elsevier
• Subjects: Aggression - physiology; amygdala; Analysis of Variance; Animals; anxiety; AOB; Behavior, Animal; Biological and medical sciences; Brain - metabolism; c-Fos; Cats; Escape Reaction - physiology; Foxes; Fundamental and applied biological sciences. Psychology; Male; Neurology; Odorants; olfaction; Olfactory Bulb; Olfactory Pathways - physiology; Olfactory system and olfaction. Gustatory system and gustation; predator; Proto-Oncogene Proteins c-fos - metabolism; Rats; Smell - drug effects; Smell - physiology; Vertebrates: nervous system and sense organs; amygdala; PMd; HDB; c-Fos; olfaction; phosphate buffer; phosphate-buffered saline; ACo; ventral orbital cortex; AOB; analysis of variance; ANOVA; central amygdala; PBH; CnF; cuneiform nucleus; horizontal limb of the diagonal band of Broca; PBS; MOB; predator; trimethylthiazoline; phosphate-buffered horse serum; anxiety; PB; main olfactory bulb; anterior cortical amygdala; PAG; VO; TMT; accessory olfactory bulb; dorsal premammillary nucleus; CeA; periaqueductal gray; Fissipedia; Carnivora; Amygdala; Rat; fos Gene; Rodentia; Central nervous system; Basal ganglion; Fox; Encephalon; Vertebrata; Mammalia; Animal; Cat; Olfaction; Anxiety; Odor; Protooncogene; Immediate early gene
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2007.11.039

Abstract Cat odor and trimethylthiazoline (TMT, a component of fox feces) are two stimuli widely used in rodent models of fear and anxiety. Recent studies suggest that these odorants have distinct behavioral effects, raising questions as to whether TMT is a true “predator odor.” Here we used c-Fos immunohistochemistry to compare patterns of neural activation produced by cat odor and TMT. Rats were exposed to either (1) three pieces of a collar that had been worn by a domestic cat, (2) three collar pieces impregnated with TMT (30 μl/piece), (3) three collar pieces impregnated with 4% formaldehyde (200 μl/piece, an acrid but non-predatory odor), or (4) three control (no odor) collar pieces. Odors were presented in a small well-ventilated plastic box. All odorants (cat odor, TMT and formaldehyde) produced increased defecation in rats compared with the control group, and formaldehyde exposure also decreased rearing. Cat odor increased contact with the stimulus relative to all other groups, while TMT increased contact compared with the formaldehyde and clean air groups. Only cat odor decreased grooming and elicited escape attempts. In addition, only cat odor caused pronounced activation of Fos in the accessory olfactory bulb and its projection areas, anterior olfactory nucleus, medial prefrontal cortex, striatum, and a medial hypothalamic circuit associated with defensive behavior. In contrast, the only areas activated by TMT were the internal granular layer of the main olfactory bulb and central amygdala, while both cat odor and TMT activated the glomeruli of the main olfactory bulb, piriform cortex, ventral orbital cortex and anterior cortical amygdala. Results indicate that the effects of cat odor and TMT are easily distinguished both behaviorally and at a neural level, and suggest that TMT lacks the “pheromone-like” quality of cat odor that engages key hypothalamic sites involved in defensive behavior.