Human cocaine- and amphetamine-regulated transcript (CART) mRNA is highly expressed in limbic- and sensory-related brain regions

Cocaine- and amphetamine-regulated transcript (CART) is a novel putative pe ptide neurotransmitter. We studied the expression of CART mRNA throughout t he human postmortem brain by using in situ hybridization histochemistry. Th e cortical expression was distinct with high mRNA expression levels in the piriform cortex, dorsolateral prefrontal cortex, lateral orbital prefrontal cortex, medial orbitofrontal cortex, and middle temporal cortex, but extre mely low levels in immediately adjacent cortical areas, e.g., the medial pr efrontal cortex, subcallosal gyrus, and superior temporal cortex. Within th e striatum CART mRNA was only detected in the nucleus accumbens, primarily in the most medial area. No positive CART mRNA-expressing neurons were foun d in the dorsal caudate nucleus and putamen. High mRNA expression levels we re evident within the bed nucleus of the stria terminalis as well as the am ygdala (central, cortical, and medial nuclei). In the hippocampus, intense expression was found within the uncal gyrus and moderate to high levels in the CA3 and polymorphic layer of the dentate gyrus. CART mRNA expression wa s also detected in the locus coeruleus and dorsal raphe, but no positive la beling was apparent in the substantia nigra. Overall, the most abundant CAR T mRNA expression levels in the human brain were detected within in the hyp othalamus (posterior, paraventricular nucleus, premammillary, tuberomamilla ry, dorsomedial, arcuate) and the thalamus (mediodorsal, pulvinar, anterior , zona incerta, geniculate). Rat brain specimens were also studied and many similarities to the human CART mRNA expression were evident. However, the most marked species difference was the virtual absence of the CART mRNA in the rat thalamus. (C) 2000 Wiley-Liss, Inc.