Overexpression of dopamine receptor genes and their products in the postnatal rat brain following maternal n‐3 fatty acid dietary deficiency

A combination of PCR‐Select cDNA subtraction and gene array hybridization was used to identify differentially expressed genomic markers in brains of rats fed for 3 weeks in utero and 2 weeks after birth on an n‐3 polyunsaturated fatty acid (PUFA)‐deficient diet supplied to dams. Total RNA was isolated, switch mechanism at 5′‐end of the RNA transcripts (SMART) applied and used for PCR‐Select subtraction of PUFA‐deficient and adequately‐fed control preparations. Subtracted and amplified ds‐cDNA end‐products were fragmented, terminally labeled with biotin‐ddUTP and hybridized with a RN‐U34A gene array. A 10‐fold increase in potential genes with log2(Tester/Driver) = 1.4 was found compared with traditional gene array technology when the same chip was tested using non‐subtracted targets. Reverse transcription–real‐time relative PCR confirmed 30% of the transcripts. Among the validated transcripts, D1 and D2 receptors for dopamine (DA), were most prominent among a number of over‐expressed neurotransmitter receptors and retinoic acid receptor (RXR α‐2 and α‐1). Immunohistochemical staining of brain sections from 2‐week‐old pups revealed a substantial enrichment of the D2 receptor in discrete regions of the mesolimbic and mesocortical pathways as well as in a large number of brain areas from the n‐3 PUFA‐deficient pups. Punches of the same areas run on western blots showed similar results. The overwhelming expression of D1 and D2 receptors may be attributed to a behavioral hypersensitivity caused by the possible impairment of DA production during brain development, which may have implications in certain disorders of the nervous system.