Psychomotor stimulant- and opiate-induced c-fos mRNA expression patterns in the rat forebrain: Comparisons between acute drug treatment and a drug challenge in sensitized animals

Amphetamine-, cocaine-, and morphine-induced c-fos expression patterns were examined following an injection protocol that has previously been shown to produce behavioral sensitization and enhanced dopamine release in the striatal complex. Drug-specific c-fos patterns were observed in both acute and sensitization injection paradigms. A sensitization pretreatment schedule did, however, alter the c-fos expression patterns induced by all the drugs in the caudate putamen, nucleus accumbens, and the cerebral cortex. In some striatal and cortical regions, there was an increase or recruitment of cells expressing c-fos whereas in others there was an apparent decrease or inhibition. The somatosensory cortex was one area where pretreatment with all three drugs increased c-fos expression. The results suggest that the neuronal networks that are modulated by systemic drug injections in the sensitized animal differ from those affected by the initial drug exposure; areas of overlap may indicate common ‘sensitization’ circuits. Special issue dedicated to Dr. Eric J. Simon.     

Purification and characterization of interferon-like antiviral protein derived from flatfish (Paralichthys olivaceus) lymphocytes immortalized by oncogenes

Flatfish leukocytes were transfected with the expression plasmids of the v-myc, c-myc, c-fos, v-myb and c-Ha-ras oncogenes. Only cotransfection of c-Ha-ras with c-myc or c-fos resulted in complete immortalization of the cells. Interferon-like anti-viral protein was found in the cultured medium of the immortalized lymphocytes. The protein was purified by DEAE-Toyopearl 650 M ion exchange chromatography and WGA agarose affinity chromatography. The protein was a glycoprotein of about 16 kDa. The antiviral activity of the protein was trypsin-sensitive and was fairly stable at pH values from 4 to 8. The protein retained about 60% of the activity even at 60°C and showed a broad antiviral activity for various fish cells and viruses.     

c-fos expression in the amygdala:In vivo antisense modulation and role in anxiety

Summary 1. The amygdaloid complex is a key structure in mechanisms of fear and anxiety. Expression of the immediate-early gene c-fos has been reported in the central nucleus of the amygdala following various stressors, but the functional role of this phenomenon has remained unknown.2. c-fos expression was observed in the central nucleus when rats were subjected to a pharmacologically validated animal model of anxiety, the Vogel conflict test, but not after mere exposure to the test apparatus. Bilateral amygdala injection of a 15-mer phosphorothioate c-fos antisense oligodeoxynucleotide prior to testing blocked conflict-induced c-fos expression and had behavioral effects similar to those of established antianxiety drugs.3. Separate experiments determined that antisense treatment did not affect conflict behavior by acting on shock thresholds or drinking motivation.4. These findings provide evidence that neuronal activation and c-fos induction in the amygdala may be of importance for mechanisms of fear and anxiety.     

The application of antisense oligonucleotide technology to the brain: Some pitfalls

Summary 1. Amphetamine-induced c-fos andegr-1 expression in the striatum was used as a model in which to study the effects of antisense oligodeoxynucleotides (ODNs) directed at c-fos. Using direct infusions of ODNs into the striata of animals we have demonstrated that c-fos antisense ODNs retain most of their biological activity with 2- or 3-base substitutions. The c-fos antisense and mismatch ODNs attenuated Fos immunoreactivity but had little effect on Egr-1 immunoreactivity.2. In another group of studies examining the role of c-fos in amygdala kindling, we have demonstrated that ODNs cause neurotoxic damage following repeated daily infusions into the amygdala. The damage observed was greatly diminished when the time interval between infusions was extended.     

Reduced induction of c-fos but not of c-myc expressions in a nontumorigenic revertant R1 of EJ-ras-transformed NIH/3T3 cells treated with 12-O-tetradecanoylphorbol-13-acetate (TPA)

It has been reported that both c-fos and c-myc mRNAs are induced in NIH/3T3 cells after 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment. We have studied the effect of TPA on the expression of c-fos and c-myc in EJ-ras-transformed NIH/3T3 and its nontumorigenic flat revertant R1 cells. Although TPA treatment induces c-myc mRNA, as in the case of NIH/3T3 cells, the induced level of c-fos mRNA is greatly reduced not only in slow-growing EJ-ras-transformed NIH/3T3 but also in quiescent R1 cells. In addition, serum-induced c-fos expression is also reduced in EJ-ras-transformed NIH/3T3 and R1 cells. These observations suggest that the pathway from TPA to c-fos gene is different from that to c-myc gene and that the former pathway is down-regulated in association not with the transformed phenotype, but with EJ-ras expression, and it is possible that this reduced induction of c-fos is not specific to TPA.     

c-Fos Expression by Dopaminergic Receptor Activation in Rat Hippocampal Neurons

While dopamine is likely to modulate hippocampal synaptic plasticity, there has been little information about how dopamine affects synaptic transmission in the hippocampus. The expression of IEGs including c-fos has been associated with late phase LTP in the CA1 region of the hippocampus. The induction of c-fos by dopaminergic receptor activation in the rat hippocampus was investigated by using semiquantitative RT-PCR and immuno-cytochemistry. The hippocampal slices which were not treated with dopamine showed little expression of c-fos mRNA. However, the induction of c-fos mRNA was detected as early as 5 min after dopamine treatment, peaked at 60 min, and remained elevated 5 h after treatment. Temporal profiles of increases in c-fos mRNA by R(+)-SKF-38393 (50 M) and forskolin (50 M) were similar to that of dopamine. An increase in [cAMP] was observed in dopamine-, SKF-, or forskolin-treated hippocampal slices. By immunocytochemical studies, control hippocampal cells showed little expression of c-Fos immunoreactivity. However, when cells were treated with dopamine, an increase in the expression of c-Fos immunoreactivity was observed after treatment for 2 h. The treatment of hippocampal neurons with R(+)-SKF38393 (50 M) or forskolin (50 M) also induced a significant increase in c-Fos expression. These results indicate that the dopamine D1 receptor-mediated cAMP dependant pathway is associated with the expression of c-Fos in the hippocampal neurons. These data are consistent with the possible role of endogenous dopamine on synaptic plasticity via the regulation of gene expression. Furthermore, these results imply that dopamine might control the process of memory storage in the hippocampus through gene expression.     

Secretin Activates Visceral Brain Regions in the Rat Including Areas Abnormal in Autism

1. The aim of this study was to determine whether central networks are involved in the presumptive behavioral and autonomic regulatory actions of secretin, a gut hormone that has been reported to have ameliorative effects in autistic children.2. Central neural responses monitored by regional c-fos gene expression were examined in response to intracerebroventricular secretin injection in awake, freely-moving Sprague-Dawley rats. Tissue sections were incubated in an antibody to the c-fosgene product, Fos, and processed immunohistochemically.3. Qualitative differences in Fos immunoreactivity in stress adaptation and visceral representation areas of the brain were observed between secretin- and vehicle-infused age-matched pairs (n = 4 pairs). Secretin-activated regions include the area postrema, dorsal motor nucleus, medial region of the nucleus of the solitary tract and its relay station in the lateral tegmentum, locus ceruleus, ventral periaqueductal gray, periventricular thalamic nucleus, paraventricular hypothalamus magnocellularis, medial and central amygdala, lateral septal complex as well as ependymal and subependymal nuclei lining the third ventricle. Specific areas of the cerebral cortex were heavily labeled in secretin-treated rats, as compared to controls: the medial bank of the anterior prefrontal cortex, orbitofrontal cortex, the piriform cortex, and the anterior olfactory nucleus. Secretin attenuated Fos immunoreactivity in the dorsal periaqueductal gray, intralaminar thalamus, medial parvicellular compartment of the hypothalamus, supraoptic nucleus of the hypothalamus, lateral amygdala, motor cortex, and the somatosensory and association areas of the parietal cortex.4. Secretin alters the activity of structures involved in behavioral conditioning of stress adaptation and visceral reflex reactions. This study predicts a possible cellular mechanism, activation of third ventricular ependymal and subependymal cells, as well as central regulatory actions of secretin. The physiological effects of secretin on behavioral, endocrine, autonomic and sensory neuronal activation patterns, together, contribute to central c-fos activation. Secretin alters the activity of structures involved in behavioral conditioning of stress adaptation and visceral reflex reactions. This study predicts a possible cellular mechanism, activation of third ventricular ependymal and subependymal cells, and central regulatory actions of secretin. The physiological effects of secretin on behavioral, endocrine, autonomic and sensory neuronal activation patterns, together, contribute to central c-fos activation. These findings mandate further investigation of secretin as a brain/gut stress regulatory hormone.     

Effect of the Tumor Promoter Phorbol 12-Myristate 13-Acetate (PMA) on Proliferation of Young and Senescent WI-38 Human Diploid Fibroblasts

The effects of the tumor promoter phorbol 12-myristate 13-acetate (PMA) on the proliferation, protein kinase C activity (PKC), and c-fos gene expression were examined in cultures of young and senescent (90-95% lifespan completed) WI-38 human diploid fibroblasts. We observed that, following stimulation with medium containing 10% fetal bovine serum (FBS), the translocation of PKC from the cytosol to the particulate compartment was less efficient in senescent WI-38 cells than in young cells. However, when PMA was added to the medium, the intracellular distribution of PKC activity in old cells became nearly identical to that observed in young cells. The inducibility of c-fos mRNA by serum addition, which is a protein kinase C-dependent event [64], was significantly amplified in the presence of PMA. Moreover, the duration of peak c-fos expression, after stimulation by FBS and PMA, increased in senescent cells as compared to young cells. Our results reveal that the normal signal transduction pathway is altered in senescent, slowly proliferating human fibroblasts and that it can be partially restored in the presence of the tumor promoter PMA.