VIP in the rat brain: evidence for a major pathway linking the amygdala and hypothalamus via the stria terminalis.

We report here on the detailed distribution of VIP-like immunoreactivity in the rat brain by a combined immunological approach using immunocytochemistry and radioimmunoassay. VIP-like immunoreactivity was widely distributed. Cell bodies and and fibres were noted principally in the cortex, hippocampus, amygdala, suprachiasmatic nucleus and brain stem. In addition dense areas of immunoreactive fibres and terminals were seen in the stria terminalis and its bed nucleus. The fibres appear to form a major VIP-containing pathway which links the amygdaloid complex with the hypothalamus. Although the functional significance of VIP in the brain is unknown, its presence in the amygdala, the hypothalamus and their linking pathway, as well as its pharmacological actions suggest that it may play a role in neuroendocrine regulation and the modulation of hypothalamic function.