The distribution of galanin mRNA-expressing cells and galanin-immunoreactive (IR) cell bodies and processes was studied in the brain of mice overexpressing galanin under the PDGF-B promoter (GalOE mice) and of wild type (WT) mice, both in colchicine-treated and non-treated animals. In this abstract, we only describe the results in GalOE mouse. A widespread ectopic expression of galanin (both mRNA and peptide) was found, that is a situation when neither transcript nor peptide could be seen in WT mice, not even after colchicine treatment. However, in some regions, such as claustrum, basolateral amygdala, thalamus, CA1 pyramidal cells, and Purkinje cells only galanin mRNA could be detected. In the forebrain galanin was seen in the mitral cells of the olfactory bulb, throughout the cortex, in the basolateral amygdaloid nucleus, claustrum, granular and pyramidal cell layers of the hippocampus, subiculum and presubiculum. In the thalamus, the anterodorsal, mediodorsal, intermediodorsal and mediodorsal lateral nuclei, the reuniens and reticular nuclei showed ectopic expression of galanin. Within the hypothalamus, neurons of the suprachiasmatic nucleus contained galanin. In the mesencephalon, the geniculate nucleus, nucleus ruber, the mesencephalic trigeminal and reticulotegmental nuclei ectopically expressed galanin. In the cerebellum, galanin was observed in the Purkinje cells and in the lateral and interposed cerebellar nuclei. In the pons, sensory and motor nuclei of the trigeminal nerve, the laterodorsal and dorsal tegmental nuclei, the pontine, reticulotegmental and gigantocellular reticular nuclei expressed galanin. Within the medulla oblongata, labeled cells were detected in the facial, ambiguus, prepositus, lateral paragigantocellular and lateral reticular nuclei, and spinal trigeminal nucleus. High densities of galanin-IR fibers were found in the axonal terminals of the lateral olfactory tract, the hippocampal and presumably the cerebellar mossy fibers system, in several thalamic and hypothalamic regions and the lower brain stem. Possible functional consequences of galanin overexpression are discussed.