Abstract
It has been demonstrated that the basolateral nucleus of the amygdala contains pyramidal neurons that project to medial prefrontal cortex, the rat correlate of anterior cingulate cortex in humans. It also has been observed that this nucleus contains neurons enriched with synaptic zinc that appear to have pyramidal cell bodies. In the present series of experiments, it was demonstrated using retrograde tracing with FluoroGold and autometallographic labeling of zinc-enriched neurons that a large percentage of those pyramidal neurons projecting to medial prefrontal cortex contain synaptic zinc. Preliminary findings indicate that the majority of these zinc-enriched neurons do not innervate medial prefrontal cortex until after post-natal day 38 of the rat. The discovery of these neurons, and their late development, has potentially important implications in psychiatric disease, particularly schizophrenia. It was also determined that future experiments to analyze the development of this cortico-limbic pathway would require a means to chronically administer psychoactive agents to the postnatal amygdala while causing minimal trauma. To achieve this end, a chronic infusion system was devised utilizing a 50 ~-tm diameter microcannula to deliver agent driven by a miniosmotic pump.