Long term effects of adolescent chronic mild stress on brain catecholamine transmission in rat brain: a microdialysis study

Aims: Although the aetiology of depression is largely unknown, it is widely accepted that epigenetic factors such as chronic stress may have a prominent role in the manifestation of this illness. We previously observed that young adult rats born from dams exposed to restrain stress in the last week of pregnancy had basal and stimulated catecholamine transmission alteration in the nucleus accumbens (NAcc) (Silvagni A. 2008). We intended to study the alteration of catecholamine transmission in the NAcc shell of adult rats exposed to unpredictable chronic stress (UCMS) at adolescent age to shed light on depression aetiology. Methods: By means of microdialysis we studied basal and stimulated dopamine and noradrenaline release in the NAcc shell of adult rats that were exposed UPS at peri-adolescent age (28-42 PND). Results: We observed that UPS determined i) an increased basal level of dopamine but not noradrenaline in the NAcc.; ii) a reduced response to amphetamine (0.5 mg/kg ip) of both dopamine and noradrenaline release; iii) an increased response to the dopamine reuptake blocker GBR 12909 (10 mg/kg ip) to dopamine but not noradrenaline release. Conclusions: These results suggest that catecholamine transmission in the Nacc shell is involved long term effect of UCMS. In particular we can hypothesize that dopamine basal release and reuptake may be correlated with vesicular dopamine content and mobilization and a dysfunction of this process may be linked to anhedonia and in turn involved in the aetiology of depression