Brain Research 961 (2003) 166–170 www.elsevier.com / locate / brainres Short communication Fox odour affects corticosterone release but not hippocampal serotonin reuptake and open field behaviour in rats a,b a a a Danusa Dias Soares , Francesca Fernandez , Sylvie Aguerre , Aline Foury , a a, * ` Pierre Mormede , Francis Chaouloff a ¨ INSERM U471-INRA, Institut F. Magendie, Rue Camille Saint Saens, 33077 Bordeaux, France b Laboratory of Exercise Physiology, Department of Physical Education, Federal University of Minas Gerais, Belo Horizonte, MG, 31270-901 Brazil Accepted 8 November 2002 Abstract Group-housed Sprague–Dawley (SD) rats exposed for 1 h to 2,5-dihydro-2,4,5-trimethylthiazoline (TMT, a component of fox feces) 3 did not display changes in hippocampal serotonin (5-HT) metabolism and [ H]5-HT reuptake, compared to water or butyric acid. Such an observation extended to isolated SD and Fischer 344 rats. When group-housed SD rats were tested 1 week after a 1-h exposure to TMT, 3 3 hippocampal 5-HT metabolism, [ H]5-HT reuptake, and [ H]paroxetine binding at the 5-HT transporter remained unchanged. This study questions TMT as a specific predatory stimulus as both butyric acid and TMT increased plasma corticosterone levels whilst leaving intact open field behaviour (at least in group-housed SD rats).  2002 Elsevier Science B.V. All rights reserved. Theme: Neurotransmitters, modulators, transporters, and receptors Topic: Serotonin Keywords: 2,5-Dihydro-2,4,5-trimethylthiazoline; Serotonin transport; 5-Hydroxyindoleacetic acid; Open field behavior; Rat strain; Housing conditions The impact of stress on central serotonergic systems has cate that hippocampal 5-HT reuptake may be altered by been well-documented: thus, 5-HT nerve firing (but see natural environmental changes, but not by intrusive phys- Ref. [15]), synthesis / metabolism and release of 5-HT, as ical stressors. Against this hypothesis, however, is one well as the sensitivity of several 5-HT receptors may vary study using another naturalistic stressor, i.e. predator with the nature, intensity, and duration of the stress odour, where hippocampal 5-HT reuptake did not vary in stimulus [5,6]. On the other hand, how stress affects rats exposed for 5 min to cat odour [12]. neuronal reuptake of 5-HT through the membrane 5-HT In keeping with the aforementioned hypothesis that transporter (5-HTT), i.e. a variable that influences extracel- natural stressors may affect hippocampal 5-HT reuptake, lular 5-HT and then neurotransmission, is still under the present study examined whether the negative observa- debate. Thus, brief noise stress [18] or 5-min exposure to a tion in rats exposed to cat odour extended to another novel environment [11,12] were found to diminish hip- predator odour. Actually, one predator odour which has pocampal 5-HT reuptake whereas neither forced swim- received much attention recently is 2,5-dihydro-2,4,5-tri- ming, treadmill running, or restraint for 30 min affected methylthiazoline (TMT), a compound isolated from fox such a variable [16]. It is likely that this heterogeneity of feces, as it has been shown to activate the hypothalamo– results reflects the application of different stress stimuli, pituitary–adrenal axis [7,19,23], to elicit several fear-re- different stress durations, and / or different rat strains. With lated behaviours [24] (but see below), and to stimulate regard to the former hypothesis, these results could indi- stress-related frontocortical and amygdala dopaminergic systems in rodents [19], when compared to other novel odors. Because the psychoneuroendocrine reactions to *Corresponding author. Tel.: 133-557-573-757; fax: 133-557-573- either TMT or fox urine depend on both the genetic status 752. E-mail address: francis.chaouloff@bordeaux.inserm.fr (F. Chaouloff). of the animal and its environment [1,14,24], we first used a 0006-8993 / 02 / $ – see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0006-8993(02)03944-6