Suppression of ovarian hormones in adolescent rats has no effect on anxiety‐like behaviour or c‐fos activation in the amygdala. (15th September 2020)

• Record Type: Journal Article
• Authors: Hodgson, Amy R.; Richmond, Claire; Tello, Javier; Brown, Gillian R.
• Is Part Of: Journal of neuroendocrinology. Volume 32:Number 9(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-15
• Subjects: Antide -- LH -- progesterone -- puberty -- sex difference; Neuroendocrinology -- Periodicals; 616.4
• DOI: 10.1111/jne.12897
• Languages: English
• ISSNs: 0953-8194

Abstract

Abstract: In humans, sex differences in mood disorders emerge during adolescence, with prevalence rates being consistently higher in females than males. It has been hypothesised that exposure to endogenous ovarian hormones during adolescence enhances the susceptibility of females to mood disorders from this stage of life onwards. However, experimental evidence in favour of this hypothesis is lacking. In the present study, we examined the long‐term effects of suppressing adolescent gonadal hormone levels in a group of female Lister‐hooded rats via administration of a gonadotrophin‐releasing hormone antagonist (Antide; administered on postnatal day [PND] 28 and 42) compared to control females and males (n = 14 per group). We predicted that, in adulthood, Antide‐treated female rats would exhibit more male‐like behaviour than control females in novel environments (elevated‐plus maze, open field and light‐dark box), in response to novel objects and novel social partners, and in an acoustic startle task. Progesterone and luteinising hormone assays (which were conducted on blood samples collected on PND 55/56 and 69/70) confirmed that the hypothalamic‐pituitary‐gonadal axis was temporarily suppressed by Antide treatment. In addition, Antide‐treated females were found to exhibit a modest pubertal delay, as measured by vaginal opening, which was comparable in length to the pubertal delay that has been induced by adolescent exposure to alcohol or stress in previous studies of female rats. However, Antide‐treated females did not substantially differ from control females on any of the behavioural tests, despite the evidence for predicted sex differences in some measures. Following the acoustic startle response task, all subjects were culled and perfused, and c‐Fos staining was conducted in the medial and basolateral amygdala, with the results showing no significant differences in cell counts between the groups. These findings suggest that ovarian hormone exposure during adolescence does not have long‐term effects on anxiety‐related responses in female rats. Abstract : Manipulating gonadal hormone levels during adolescence has been shown to have long‐term effects on behavioural development and brain function in male rodents. Fewer studies have investigated similar effects in female rodents. We suppressed gonadal hormone production in female Norway rats during adolescence using a GnRH antagonist, Antide. Although puberty was delayed in the experimental group, Antide‐treated females did not differ from control females in anxiety‐like behaviour, social behaviour or c‐fos activation in the amygdala in response to aversive acoustic stimuli.