Temporal dysregulation of cortical gene expression in the isolation reared Wistar rat.

The critical sequence of molecular, neurotransmission and synaptic disruptions that underpin the emergence of psychiatric disorders like schizophrenia remain to be established with progress only likely using animal models that capture key features of such disorders. We have related the emergence of behavioural, neurochemical and synapse ultrastructure deficits to transcriptional dysregulation in the medial prefrontal cortex of Wistar rats reared in isolation. Isolation reared animals developed sensorimotor deficits at postnatal day 60 which persisted into adulthood. Analysis of gene expression prior to the emergence of the sensorimotor deficits revealed a significant disruption in transcriptional control, notably of immediate early and interferon-associated genes. At postnatal day 60 many gene transcripts relating particularly to GABA transmission and synapse structure, for example Gabra4, Nsf, Syn2 and Dlgh1, transiently increased expression. A subsequent decrease in genes such as Gria2 and Dlgh2 at postnatal day 80 suggested deficits in glutamatergic transmission and synapse integrity, respectively. Microdialysis studies revealed decreased extracellular glutamate suggesting a state of hypofrontality while ultrastructural analysis showed total and perforated synapse complement in layer III to be significantly reduced in the prefrontal cortex of postnatal day 80 isolated animals. These studies provide a molecular framework to understand the developmental emergence of the structural and behavioural characteristics that may in part define psychiatric illness.

Learning-associated regulation of polysialylated neural cell adhesion molecule expression in the rat prefrontal cortex is region-, cell type- and paradigm-specific.

The prefrontal cortex (PFC) is an interconnected set of cortical areas that function in the synthesis of a diverse range of information and production of complex behaviour. It is now clear that these frontal structures, through bidirectional excitatory communication with the hippocampal formation, also play a substantial role in long-term memory consolidation. In the hippocampus, morphological synaptic plasticity, supported by regulation of neural cell adhesion molecule (NCAM) polysialylation status, is crucial to information storage. The recent description of polysialylated neurons in the various fields of the medial PFC suggests these structures to possess a similar capacity for synaptic plasticity. Here, using double-labelling immunohistochemistry with glutamic acid decarboxylase 67, we report that the nature of NCAM polysialic acid-positive neurons in the PFC is region-specific, with a high proportion (30-50%) of a gamma-aminobutyric acid (GABA)ergic phenotype in the more ventral infralimbic, orbitofrontal and insular cortices compared with just 10% in the dorsal structures of the cingulate, prelimbic and frontal cortices. Moreover, spatial learning was accompanied by activations in polysialylation expression in ventral PFC structures, while avoidance conditioning involved downregulation of this plasticity marker that was restricted to the dorsomedial PFC--the cingulate and prelimbic cortices. Thus, in contrast to other structures integrated functionally with the hippocampus, memory-associated plasticity mobilized in the PFC is region-, cell type- and task-specific.

Human cytochrome p450 enzymes of importance for the bioactivation of methyleugenol to the proximate carcinogen 1'-hydroxymethyleugenol.

In vitro studies were performed to elucidate the human cytochrome P450 enzymes involved in the bioactivation of methyleugenol to its proximate carcinogen 1'-hydroxymethyleugenol. Incubations with Supersomes, expressing individual P450 enzymes to a high level, revealed that P450 1A2, 2A6, 2C9, 2C19, and 2D6 are intrinsically able to 1'-hydroxylate methyleugenol. An additional experiment with Gentest microsomes, expressing the same individual enzymes to roughly average liver levels, indicated that P450 1A2, 2C9, 2C19, and 2D6 contribute to methyleugenol 1'-hydroxylation in the human liver. A study, in which correlations between methyleugenol 1'-hydroxylation in human liver microsomes from 15 individuals and the conversion of enzyme specific substrates by the same microsomes were investigated, showed that P450 1A2 and P450 2C9 are important enzymes in the bioactivation of methyleugenol. This was confirmed in an inhibition study in which pooled human liver microsomes were incubated with methyleugenol in the presence and absence of enzyme specific inhibitors. Kinetic studies revealed that at physiologically relevant concentrations of methyleugenol P450 1A2 is the most important enzyme for bioactivation of methyleugenol in the human liver showing an enzyme efficiency (kcat/Km) that is approximately 30, 50, and > 50 times higher than the enzyme efficiencies of, respectively, P450 2C9, 2C19, and 2D6. Only when relatively higher methyleugenol concentrations are present P450 2C9 and P450 2C19 might contribute as well to the bioactivation of methyleugenol in the human liver. A 5-fold difference in activities was found between the 15 human liver microsomes of the correlation study (range, 0.89-4.30 nmol min(-1) nmol P450(-1)). Therefore, interindividual differences might cause variation in sensitivity toward methyleugenol. Especially lifestyle factors such as smoking (induces P450 1A) and the use of barbiturates (induces P450 2C) can increase the susceptibility for adverse effects of methyleugenol.