1. ¹Department of Neurology and Neurosurgery, Centre for Neuronal Survival, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada
2. ²Center for Studies in Behavioral Neurobiology, Department of Psychology, Concordia University, Montreal, Quebec, Canada
3. ³Cone Laboratory, Department of Neurology and Neurosurgery, Centre for Neuronal Survival, Montreal Neurological Institute, McGill University, Montreal, Quebec, Canada

Correspondence: Dr C Flores and TE Kennedy, E-mails: cecilia.flores@mcgill.ca, timothy.kennedy@mcgill.ca

^*Current address: Department of Psychiatry, McGill University, Douglas Hospital Research Centre, 6875 LaSalle Blvd., Verdun, Quebec, Canada H4H 1R3.

Received 29 April 2004; Revised 13 August 2004; Accepted 23 September 2004; Published online 9 November 2004.

Abstract

Netrins are guidance cues that play a fundamental role in organizing the developing brain. The netrin receptor, DCC (deleted in colorectal cancer), is highly expressed by dopaminergic (DA) neurons. DCC may therefore participate in the organization of DA circuitry during development and also influence DA function in the adult. Here we show that adult dcc heterozygous mice exhibit a blunted behavioral response to the indirect DA agonist amphetamine and do not develop sensitization to its effects when treated repeatedly. These behavioral alterations are associated with profound changes in DA function. In the medial prefrontal cortex, dcc heterozygotes exhibit increased tyrosine hydroxylase (TH) protein levels and dramatic increases in basal concentrations of DA and DA metabolites. In contrast, in the nucleus accumbens, dcc heterozygotes show no changes in either TH or DA levels, but exhibit decreased concentrations of DA metabolites, suggesting reduced DA activity. In addition, dcc heterozygous mice exhibit a small, but significant reduction in total number of TH-positive neurons in midbrain DA cell body regions. These results demonstrate for the first time that alterations in dcc expression lead to selective changes in DA function and, in turn, to differences in DA-related behaviors in adulthood. These findings raise the possibility that changes in dcc function early in life are implicated in the development of DA dysregulation observed in certain psychiatric disorders, such as schizophrenia, or following chronic use of drugs of abuse.