Administration of morphine and/or cocaine modulates the expression levels of genes related to plasticity mechanisms in rat hippocampus

Drugs of abuse regulate the expression of several genes involved in receptor regulation and signalling, transcription factors and cytoskeleton proteins. Due to its implication in long-term memory consolidation, rat hippocampus was selected to identify genes that are differently regulated by morphine and/or cocaine administration. The animals were randomly separated into four groups given saline or morphine for five days followed by an acute dose of saline or cocaine the second day after last saline/morphine injection. Quantitative real-time polymerase chain reaction was used to analyze differentiation in the mRNA level. Significant alteration in mRNA expression was observed in six genes; growth associated protein 43 (Gap43), brain-derived neurotrophic factor (Bdnf), neurotrophic tyrosine kinase receptor (trkB), fms-like tyrosine kinase 1 (Flt1), microtubule-associated protein 2 (Map2) and Ca2+/calmodulin-dependent protein kinas II (CaMK-II). These data demonstrate that administration of morphine and cocaine severally or in combination alter the expression of genes related with hippocampal structural plasticity