Cerebral blood flow and cerebrovascular permeability in an inescapable shock (learned helplessness) animal model of depression

The effects of a purported animal model of depression (inescapable shock, IS) was tested on: (a) escape behavior, (b) regional brain levels of norepinephrine (NE), serotonin (5-HT), and dopamine, and (c), the response of the cerebromicrovasculature to metabolic demand as mimicked by manipulation of arterial CO₂ content (PaCO₂). Multidisciplinary research has implicated central biogenic amines in the regulation of cerebromicrocirculation. IS treatment resulted in increased escape latency and lowered levels of NE and 5-HT in the locus coeruleus but not in terminal fields in distant regions. This treatment also did not alter cerebral blood flow or capillary permeability in distant regions when compared with control rats. Thus, the discrete changes in NE and 5-HT in locus coeruleus induced by IS treatment is not reflected in changes in cerebral blood flow and the effective permeability of the blood-brain barrier.