The Open Neuroendocrinology Journal

2010, 3 : 52-58
Published online 2010 August 11. DOI: 10.2174/1876528901003010052
Publisher ID: TONEUROEJ-3-52

Long-Term Reduction in Anxiety Levels During the Promotion Phase of Mammary Adenocarcinoma Induced by Dimethylbenz (a) Anthracene in Female Sprague-Dawley Rats

Marianne Beau Yon DE Jonage-Canonico , Pierre L. Roubertoux , Véronique Lenoir , Michèle Carlier and Bernard Kerdelhue
Université René Descartes, Laboratoire de Neuroendocrinologie, INSERM U 648, UFR Biomédicale des Saints Pères, 45, Rue des Saints Pères, 75270-PARIS CEDEX 06, France

ABSTRACT

Background/Aims:

It has been reported that long-term neuroendocrine dysregulation of the Hypothalamic- Pituitary-Gonadal (HPG) axis and of the Hypothalamic-Pituitary-Adrenal (HPA) axis precede the appearance of mammary adenocarcinoma induced by 7, 12-Dimethylbenz(a)anthracene (DMBA) in female rats. In the present study, we investigated the hypothesis that DMBA may also induce long-term changes in anxiety levels.

Methods:

Female Sprague-Dawley rats were given a single dose of DMBA( 75 mg/kg) in 1ml sesame oil, or 1ml of sesame oil(control rats), at 55 days of age. Then,DMBA-treated and control rats were observed, monitoring their oestrous cycle. One month after administering the DMBA, anxiety levels were measured in an open-field test.The test device was an arena with a floor of 100 cm x 100 cm and a wall of 40 cm high, with white floor and walls.The floor was divided into 25 equal squares ( 16 peripheral and 9 central squares ). The statistical analysis was a two-factor analysis of variance.

Results:

Overall statistical scores showed that DMBA-treated animals had: a) greater ambulatory activity and more rearing behaviour in the central squares, but not in the peripheral squares, and b) deposited fewer faecal boli.

Conclusions:

Greater exploration of the less protected squares (in the centre), lower frequency of defecation and a greater number of rearings show a lower level of anxiety. Changes in HPG axis activity and a decrease in HPA axis activity, as previously reported, may explain the reduction in anxiety levels after treatment with the mammary carcinogen.

Keywords:

Exploratory behaviour, mammary adenocarcinoma, female rat.