Neurochemical evidence for at least two regional subdivisions within the homing pigeon (Columba livia) caudolateral neostriatum

The distributions of one neurotransmitter, two neurotransmitter-related sub stances, and five neuropeptides were examined within the homing pigeon caud olateral neostriatum (NCL). All eight neuroactive substances were found wit hin a tyrosine hydroxylase (TH)-dense region that defines the NCL. Overall regional variation in the relative density of these substances suggested at least two neurochemically distinct portions of NCL. Dorsal NCL contained r elatively dense staining for TH, choline acetyltransferase, and substance P , whereas vasoactive intestinal polypeptide was more abundant in ventral po rtions of NCL. Serotonin and cholecystokinin were found to be densest in in termediate portions of NCL. Somatostatin and leucine-enkephalin were homoge neously distributed throughout NCL. The results suggest that NCL may consis t of multiple subdivisions. Investigations into the behavioral importance o f these regions are necessary to clarify the role of this brain region in a vian behavior. (C) 1999 Wiley-Liss, Inc.