The effect of unpredictable chronic mild stress on depressive-like behavior and on hippocampal A1 and striatal A2A adenosine receptors

This study examined the effects of two chronic stress regimens upon depressive-like behavior, A(1) and A(2A) adenosine receptor binding and immunocontent. Male rats were subjected to unpredictable chronic mild stress (UCMS) or to chronic restraint stress (CRS) for 40 days. Subsequently, depressive-like behaviors (forced swimming and consumption of sucrose) were evaluated, and A(1) adenosine or A(2A) adenosine receptors were examined in the hippocampus or striatum, respectively. UCMS animals demonstrated depressive-related behaviors (decrease in sucrose consumption and increased immobility in the forced swimming test). This group also presented increased A(1) adenosine receptor binding and immunoreactivity in hippocampus, as well as increased striatal A(2A) adenosine receptor binding in the striatum, without alteration in immunoreactivity. Conversely, the chronic restraint stress group displayed only an increase in A(1) adenosine receptor binding and no alteration in the other parameters evaluated. We suggest that the alteration in adenosine receptors, particularly the upregulation of striatal A(2A) adenosine receptors following UCMS, could be associated with depressive-related behavior.