Significant Increase In c-Fos Expression Research Articles

Fos Expression Associated with the Discriminative Stimulus Effects of Methamphetamine in Rats

Methamphetamine, a psychostimulant drug, produces both acute psychomotor stimulation and long-lasting behavioral effects including addiction and psychosis. To identify anatomical substrates for the discriminative stimulus effects of methamphetamine in rats, we examined the drug discrimination-associated c-Fos expression in the brains of rats that were trained to discriminate methamphetamine from saline under a two-lever fixed ratio (FR-20) schedule of food reinforcement. c-Fos expression in the brains of rats trained to discriminate methamphetamine from saline was significantly increased in the nucleus accumbens (NAc) and the ventral tegmental area (VTA) as compared with the expression in the control rats that were maintained under the FR-20 schedule, but no alternation was observed in other areas including the cerebral cortex, caudate putamen, substantia nigra, hippocampus, amygdala, and habenulla. Methamphetamine treatment in the trained rats caused a significant increase in c-Fos expression in the VTA, and a decrease in the NAc core, as compared to saline treatment. However, c-Fos expression in the NAc and VTA of rats that received chronic intermittent methamphetamine administration without discrimination training, did not differ from the expression in saline-treatment animals. These results suggest that the VTA and the NAc play an important role in the discriminative stimulus effects of methamphetamine.

Expression of c-fos in gastric myenteric plexus and spinal cord of rats with cervical spondylosis

To determine the expression of c-fos in gastric myenteric plexus and spinal cord of rats with cervical spondylosis and its clinical significance. A cervical spondylosis model was established in rats by destroying the stability of cervical posterior column, and the cord segments C(4-6) and gastric antrum were collected 3, 4 and 5 mo after the operation. Rats with sham operation were used as controls. c-fos neuronal counter-staining was performed with an immunohistochemistry method. Every third sections from C(4-6) segments were drawn. The 10 most labeled c-fos-immunoreactive (Fos-IR) neurons were counted, and the average number was used for statistical analysis. The mean of Fos-IR neurons in myenteric plexus was calculated after counting Fos-IR neurons in 25 ganglia from each antral preparation, and expressed as a mean count per myenteric ganglion. There were a few c-fos-positive neurons in the cervical cord and antrum in the control group. There was an increased c-fos expression in model group 3, 4 and 5 mo after operation, whereas there was no significant increase in c-fos expression in the control group at 3, 4 and 5 mo. More importantly, there was a significant difference in c-fos expression between rats followed up for 3 mo and those for 5 mo in the model group (11.20+/-2.26 vs 27.68+/-4.36, P<0.05, for the cervical cord; and 11.3+/-2.3 vs 29.3+/-4.6, P<0.05, for the gastric antrum). There was no significant difference between rats followed up for 3 mo and those for 4 mo and between rats followed up for 4 mo and those for 5 mo in the model group. c-fos expression in gastric myenteric plexus was dramatically associated with that in the spinal cord in rats with cervical spondylosis, suggesting that the gastrointestinal function may be affected by cervical spondylosis. If this hypothesis is confirmed by further studies, functional gastrointestinal diseases such as functional dyspepsia and irritable bowel syndrome could be explained by neurogastroenterology.

Afferent fibers of the hypogastric nerves are involved in the facilitating effects of chemical bladder irritation in rats.

To evaluate the role of bladder afferent fibers in the hypogastric nerves (HGN) in modulation of the micturition reflex induced by chemical bladder irritation, voiding behavior, continuous cystometry, and spinal c-fos expression following intravesical acetic acid instillation were investigated in rats with or without HGN transection. Voiding behavior and continuous cystometry were examined in unanesthetized conscious rats. Following chemical bladder irritation, a significant increase in urinary frequency associated with a marked decrease in the voided volume per micturition, was noted in control rats with the intact HGN, but not in HGN-transected rats. Continuous infusion of acetic acid in control rats elicited irritative bladder responses characterized by a marked decrease in the intercontraction interval and a marked increase in maximal vesical pressure, both of which were absent in capsaicin-desensitized rats. HGN transection prevented the decrease in the intercontraction interval but not an increase in maximal vesical pressure following chemical bladder irritation. Compared with saline infusion, acetic acid infusion caused a significant increase in c-fos expression at L(1) and L(6) of the spinal cord, and HGN transection significantly reduced c-fos expression in the dorsal horn of the spinal cord at L(1) but not at L(6). These results suggest that capsaicin-sensitive bladder afferent fibers in the HGN, which travel through the rostral lumbar spinal cord, have a role in urinary frequency caused by chemical bladder irritation.

Central galanin and N-terminal galanin fragment induce c-Fos immunoreactivity in the medulla oblongata of the anesthetized rat

This immunohistochemical study analyzed the c-Fos expression (c-Fos-ir) induced by galanin injections. Galanin and N-terminal galanin fragment (1–15) induced a significant increase of c-Fos expression (c-ir) within the medulla oblongata 90 min and 6 h. after intracisternal injections. This expression has been studied mainly in the nucleus of the solitary tract and in the ventrolateral medulla showing different temporal profiles for both peptides. The presence of c-Fos-ir in TH-positive cells was analyzed in all the groups. These results may be relevant to understand the role of galanin in several functions including central cardiovascular control.

ITF expression in mouse brain during acquisition of alcohol self-administration

Expression of inducible transcription factors (ITFs) c-Fos and FosB was investigated during acquisition of alcohol drinking in C57BL/6J mice. A slight but statistically significant increase in c-Fos expression was found in the Edinger–Westphal nucleus (EW) of animals consuming 2% ethanol/10% sucrose for the first time. Stronger expression of c-Fos in EW was found in animals repeatedly consuming ethanol-containing solutions. These findings underscore the potential importance of EW in alcohol-related behaviors.

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 immunocytochemistry. 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 microM) and forskolin (50 microM) 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 microM) or forskolin (50 microM) also induced a significant increase in c-Fos expression. These results indicate that the dopamine D1 receptor-mediated cAMP dependent 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.

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 μM) and forskolin (50 μM) 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 μM) or forskolin (50 μM) 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.

C-Fos gene expression pattern in the hypothalamus and the preoptic area of defeminized rats

The object of the present study was to determine the c-fos gene expression pattern in the hypothalamus (HYP) and the preoptic area (POA) after estradiol and testosterone priming during the critical period of sexual differentiation of the rat brain. Three-day-old female rats were injected s.c. with a single dose of 17β-estradiol (200 μg), testosterone enantate (200 μg) or vehicle (corn oil). HYP and POA were dissected 2 h, 24 h and 14 days after treatments and on the day of vaginal opening (VO). Other animals, previously treated as above, were acutely injected with 17β-estradiol (5 μg) on the day of VO; HYP and POA were obtained 3 h later. Total RNA was extracted and processed for semiquantitative RT-PCR. We observed that c-fos gene expression was markedly increased in POA of the animals treated with estradiol or testosterone 2 h after treatments, while a non-significant increase in c-fos gene expression was observed in the HYP of these animals. We found a significant increase in c-fos expression in HYP and POA on the day of VO in both estradiol and testosterone defeminized rats. Interestingly, the acute estradiol administration on the day of VO did not induce c-fos gene expression in either HYP or POA of defeminized animals, instead a diminution in its expression was observed in animals treated with testosterone in POA. The overall results suggest that estradiol and testosterone imprinting during critical postnatal period of sexual differentiation of the brain permanently modifies the regulation of c-fos gene expression.

Galanin knockout mice reveal nociceptive deficits following peripheral nerve injury.

The neuropeptide galanin has been identified as a potential neurotransmitter/neuromodulator within the central nervous system. In the present study, the role of endogenous galanin in nociceptive processing in the nervous system has been analysed by using mice carrying a targeted mutation in the galanin gene. Supporting this, the effect of chronic administration of exogenous galanin on nociceptive sensory inputs has been assayed in adult rats. In the absence of peripheral nerve injury, the sensitivity to threshold noxious stimuli is significantly higher in galanin mutant mice than wild-type controls. Following peripheral nerve injury, in conditions under which endogenous galanin levels are elevated, spontaneous and evoked neuropathic pain behaviours are compromised in mutant mice. Conversely, chronic intrathecal delivery of exogenous galanin to nerve-intact adult rats is associated with persistent behavioural hypersensitivity, a significant increase in c-fos expression and an increase in PKCgamma immunoreactivity within the spinal cord dorsal horn. The present results demonstrate that a relationship exists between the degree of nerve injury-induced galanin expression and the degree of behavioural hypersensitivity, and show that galanin may play a role in nociceptive processing in the spinal cord, with interrelated inhibitory and excitatory effects.

C-fos mRNA induction in the central and peripheral nervous systems of diisopropyl phosphorofluoridate (DFP)-treated hens.

A single dose of diisopropyl phosphorofluoridate (DFP), an organophosphorus ester, produces delayed neurotoxicity (OPIDN) in hen. DFP produces mild ataxia in hens in 7-14 days, which develops into severe ataxia or paralysis as the disease progresses. Since, OPIDN is associated with alteration in the expression of several proteins (e.g., Ca2+/calmodulin-dependent protein kinase II (CaM kinase II) alpha-subunit, tau, tubulin, neurofilament (NF) protein, vimentin, GFAP) as well as their mRNAs (e.g., NF, CaM kinase II alpha-subunit), we determined the effect of a single dose of DFP on the expression of one of the best known immediate-early gene (IEG), c-fos. C-fos expression was measured by Northern hybridization in cerebrum, cerebellum, brainstem, midbrain, spinal cord, and the sciatic nerves of hens at 0.5 hr, 1 hr, 2 hr, 1 day, 5 days, 10 days, and 20 days after a single 1.7 mg/kg, sc. injection of DFP. All the tissues (cerebrum, 52%; cerebellum, 55%; brainstem, 49%; midbrain, 23%; spinal cord, 80%; sciatic nerve, 157%) showed significant increase in c-fos expression in 30 min and this elevated level persisted at least up to 2 hr. Expressions of beta-actin mRNA and 18S RNA were used as internal controls. The significant increase in c-fos expression in DFP-treated hens suggests that c-fos may be one of the IEGs involved in the development of OPIDN.

Neural populations in the rat forebrain and brainstem activated by the suckling stimulus as demonstrated by cFos expression

During lactation in the rat, the suckling stimulus plays an important role in mediating alterations in hypothalamic neuroendocrine function associated with lactation. To provide the basis for understanding the neural circuitry that may transmit suckling-induced signals into the hypothalamus, the present study used the expression of the immediate-early gene product, cFos protein, as a marker for neuronal activation to identify neural populations in the brain of lactating female rats activated by the suckling stimulus. In addition, cFos expression induced by the exteroceptive sensory stimuli (olfactory, auditory, visual) associated with pup exposure alone was also determined. Thus, cFos patterns in response to the physical suckling stimulus, which would include exteroceptive sensory stimuli associated with pup exposure, were compared with the patterns induced in response to pup exposure alone, so that neuronal populations specifically activated by the suckling stimulus could be identified. After 90 min of suckling, several forebrain areas, including the lateral septum, medial preoptic area, periventricular preoptic area and supraoptic nucleus of hypothalamus, showed a significant increase in cFos expression, compared with non-suckled controls and pup exposure animals. In addition, in the bed nucleus of stria terminalis, the medial amygdala and several cortical areas, cFos-positive cells were found in both suckling and pup exposure animals. In the brainstem, the suckling stimulus induced a significant increase in cFos expression in the ventrolateral medulla, locus coeruleus, lateral parabrachial nucleus, lateral and ventrolateral portions of the caudal part of the periaqueductal gray, and caudal portion of the paralemniscal nucleus, compared with non-suckled controls and pup exposure animals. As expected, in several areas related with sensory input, such as reticular formation and pontine nucleus, cFos expression was found in both suckling and pup exposure animals. Moreover, when double-label immunocytochemistry was used to identify cFos- and catecholamine-positive neurons in the brainstem, it was found that catecholamine-positive neurons in the ventrolateral medulla and locus coeruleus showed a significant increase in cFos expression in response to suckling compared with non-resuckled and pup-exposure groups. Using cFos expression as a marker for neuronal activation, the present studies identified the neural populations in the brain that are activated by the suckling stimulus. By comparing the pattern of cFos expression observed in response to pup exposure alone or the suckling stimulus, the present studies differentiated the neural populations activated by the physical suckling stimulus from the populations activated by the exteroceptive sensory stimuli associated with pup exposure. These suckling-activated areas are likely candidates for playing an important role in transmitting the effects of the suckling stimulus into the hypothalamus to regulate neuroendocrine alterations associated with lactation.

Effect of pregnancy on activation of central pathways following atrial distension

Stimulation of the atrial volume receptors increases neural traffic to the ventrolateral medulla, which in turn sends output to, and receives input from, the lateral hypothalamic area. An integrated reflex and hormonal response is thus initiated. We wished to investigate first whether atrial distension results in activation of selected nuclei in the forebrain and, second, whether pregnancy modifies this response. Rats were implanted with indwelling intracardiac balloons positioned at the superior vena caval/right atrial junction. One week later, the balloons were inflated. The animals were then anesthetized, their brains fixed by perfusion, and the tissue prepared for visualization of c-fos activity. Atrial distension caused a significant increase in c-fos expression in the paraventricular nucleus, the medial preoptic area, and the lateral septum. This response was markedly attenuated in the pregnant animals. In conclusion, during pregnancy central pathways that are normally activated in responses to volume expansion, fail to respond to atrial distension. We propose that this allows blood volume to increase in the pregnant animal, without triggering homeostatic mechanisms.