c-Fos Protein Expression In Neurons Research Articles

Brain-derived neurotrophic factor in the amygdala mediates susceptibility to fear conditioning

Fear conditioning in animals has been used extensively to model clinical anxiety disorders. While individual animals exhibit marked differences in their propensity to undergo fear conditioning, the physiologically relevant mediators have not yet been fully characterized. Here, we demonstrate that C57BL/6 inbred mouse strain subjected to a regimen of chronic social defeat stress (CSDS) can be separated into susceptible and resistant subpopulations that display different levels of fear responses in an auditory fear conditioning paradigm. Susceptible mice had significantly more c-Fos protein expression in neurons of the basolateral amygdala (BLA) following CSDS and showed exaggerated conditioned fear responses, while there were no significant differences between groups in innate anxiety- and depressive-like behaviors. Through the use of conditional brain-derived neurotrophic factor (BDNF) knockout strategies, we find that elevated BLA BDNF level following fear conditioning training is a key mediator contributing to determine the levels of conditioned fear responses. Our results also show that relative to susceptible mice, resistant mice had a much faster recovery from conditioned stimuli-induced cardiovascular and corticosterone responses. Systemic administration of norepinephrine reuptake inhibitor atomoxetine increased c-Fos protein expression in BLA neurons following fear conditioning training and promoted the expression of conditioned fear in resistant mice. Conversely, administration of β-adrenergic receptor antagonist propranolol reduced fear conditioning training-induced c-Fos protein expression in BLA neurons and reduced conditioned fear responses in susceptible mice. These findings reveal a novel role for the BDNF signaling within the BLA in mediating individual differences in autonomic, neuroendocrine and behavioral reactivity to fear conditioning.

Regulation of Neuronal Activation by Alpha2A Adrenergic Receptor Agonist

Stress factors induce neuronal activation in brain areas that are related to anxiety and fear. High doses of caffeine induce neuronal activation with Ca2+ influx followed by expression of the immediate early gene c-fos. In the present study, we investigated c-Fos protein expression in stress-responsive brain areas induced by caffeine, as well as the role of alpha2A receptor in the regulation of neuronal activation. Immunohistochemical analysis showed that an acute effect of caffeine induced c-Fos protein expression in the hippocampus, the bed nucleus of stria terminalis (BNST), the lateral septum, the basolateral and central amygdala, the paraventricular hypothalamic nucleus (PVN), the locus coeruleus, and the lateral parabrachial nucleus (LPBN). However, c-Fos expression was attenuated after repeated treatment of caffeine, spaced 24 h apart, compared to a single acute effect. Alpha2A receptor activation with the agonist guanfacine attenuated the acute effect of caffeine in terms of c-Fos expression in neurons in the CA1-CA3 areas of hippocampus, the locus coeruleus and the LPBN as compared with effect of caffeine alone, whereas the number of c-Fos expressing neurons increased in the lateral septum, the dorsal BNST, the central amygdala, and the PVN, areas that are densely innervated by noradrenergic neurons. Guanfacine alone induced c-Fos protein expression in neurons in the central amygdala, the dorsal BNST, the PVN, the LPBN, and the caudal nucleus of the solitary tract. Guanfacine alone also induced phosphorylation of extracellular signal-regulated kinase 1/2 (ERK1/2) in neurons expressing c-Fos in the dorsal BNST, the central amygdala, and the LPBN. These results suggest that alpha2A receptor activation modulates synaptic transmission in neuronal circuits that are correlated with stress in vivo.

Working memory impairment and reduced hippocampal and prefrontal cortex c-Fos expression in a rat model of cirrhosis

Hepatic encephalopathy (HE) is a frequent neurological complication observed in patients with liver malfunction. Previous studies have shown memory impairment in these patients. In order to investigate brain substrates of spatial working memory impairment in chronic HE, neuronal expression of c-Fos protein was studied in an experimental model of cirrhosis. Control and cirrhotic rats were trained on a spatial working memory task in the Morris water maze (MWM). Differences between groups were found in the working memory task. Cirrhotic rats were unable to locate the platform in the retention trial. Neuronal activation, measured by c-Fos protein, was compared between groups. No differences were found in c-Fos expression of control and cirrhotic rats that were not tested in the MWM. Working memory task produced increase in c-Fos positive cells in dorsal hippocampus, CA1 and CA3, and prefrontal cortex in control group compared to thioacetamide group or naïve, which only swam in the maze during a similar time. These findings suggest that cirrhotic rats show spatial working memory impairment that could be linked to dysfunction in neuronal activity in prefrontal cortex and hippocampus.

Effects of treadmill running exercise on neuronal expression of c-Fos protein in the medulla oblongata after unilateral phrenicotomy in Wistar rats

The purpose of this study was to examine whether treadmill running exercise after phrenicotomy resulted in change in neuronal expression of c-Fos protein in the medulla oblongata in Wistar rats. All rats were subjected to left-sided unilateral phrenicotomy. In test experiments, rats were trained with treadmill running for 4 weeks, while in control experiments rats were not provided with the opportunity to exercise. c-Fos protein, a transient transcription factor, was immunohistochemically stained by the ABC method, and surveyed in the medulla oblongata. Numbers of c-Fos-immunoreactive (c-Fos-ir) neurons were counted microscopically, and their distribution in the medulla oblongata was mapped. In the dorsal respiratory group (DRG), numbers of c-Fos-ir neurons were found to be significantly increased in the test rats compared with control rats, while in the ventral respiratory group (VRG) no significant differences were found in numbers of c-Fos-ir neurons between test and control rats. These findings suggest that DRG neurons may play more important roles than VRG neurons in recovery of respiration in treadmill exercise after unilateral phrenicotomy in Wistar rats.

Changes in Neuronal Expression of c-Fos Protein in the Medulla Oblongata after Unilateral Phrenicotomy in Wistar Rats

[Purpose] The purpose of this study was to examine changes in neuronal expression of c-Fos protein in the medulla oblongata after unilateral phrenicotomy in Wistar rats. [Subjects and Methods] After left side phrenicotomy, rats were maintained for 4 weeks (test experiments), then transcardially perfused with fixatives. Brain sections were prepared, and c-Fos protein induced in neurons in the medulla oblongata was immunohistochemically stained by the ABC method. Control rats were maintained for the same period after sham operation, and the brain sections were similarly processed as in the test experiments. [Results] The number of c-Fos immunoreactive (c-Fos-ir) neurons in the medulla oblongata was counted and their spatial distributions were mapped. In both sides of the ventral respiratory group (VRG) and the left side of dorsal respiratory group (DRG), numbers of c-Fos-ir neurons were significantly increased in phrenicotomy rats compared to the control rats (P<0.05). In the right side of the DRG, the number of c-Fos-ir neurons also increased but without statistical significance. Numbers of c-Fos-ir neurons in the VRG were greater than that in the DRG. [Conclusion] The present results suggest that phrenicotomy may result in an increase in the activity of medullary respiratory neurons during the recovery of respiration after the phrenicotomy. The specific activation of the neurons in the VRG and DRG during unilateral phrenic nerve paralysis could underlie the changes in regulation of the respiratory control center following unilateral phrenicotomy.

Neuronal expression of c-Fos protein in the brain after intraperitoneal injection of apelin-12 in Wistar rats

Leptin has been recognized to be an important neuroendocrine signal in the regulation of food intake and energy balance. We aimed to survey central neurons that might be activated after peripheral administration of leptin, by examining the distribution of neurons expressing c-Fos protein. Leptin dissolved at a dose of 500 μg/kg in physiological saline was intraperitoneally injected in Wistar rats. One and a half hours after the injection, rats were transcardially perfused with saline and fixed with fixatives. The brain was removed and sectioned at 40 μm in thickness. Every fourth section was treated with anti-c-Fos antiserum, and c-Fos protein was immunohistochemically stained using the avidin-biotin complex method. Control rats were injected with saline solution, and brain sections were processed similarly as described above. It was found that leptin injected intraperitoneally induced the neuronal expression of c-Fos protein in several nuclei throughout the brain. In the central nucleus amygdala, ventromedial nucleus of hypothalamus, periaqueductal gray matter, lateral parabrachial nucleus, and the solitary tract nucleus, numbers of neurons expressing c-Fos protein were much more in the test experiments than those in the control experiments. Intraperitoneally injected leptin was found to stimulate central neurons that may play some roles in the regulation of such as a food intake.

C-Fos expression in supramammillary and medial mammillary nuclei following spatial reference and working memory tasks

To investigate brain substrates of spatial memory, neuronal expression of c-Fos protein was studied. Two groups of rats were trained in two spatial memory tasks in the Morris water maze, where the rats have to apply a reference memory rule or a working memory rule. In addition to the experimental groups, two control groups were used to study c- fos activation not specific to the memory processes studied. After immunohistochemical procedures, the number of c-Fos positive neuronal nuclei was quantified in the mammillary body (MB) region (medial mammillary nucleus [MMn] and supramammillary nucleus [SuM]). The results have shown that some MMn neurons expressed c-Fos nuclear immunoreactivity related to spatial working memory but not to spatial reference memory. The increased number of c-Fos immunoreactive neuronal nuclei in the SuM was related to spatial training but not to either working or reference memory demands of the tasks.

Neuronal expression of fos protein in the forebrain of diabetic rats

We sought to identify the areas that have altered neuronal activity within the hypothalamus of diabetic rats by mapping neuronal expression of c-fos protein (Fos) and Fos-related antigens. After a standard PAP immunocytochemical protocol, Fos-like immunoreactivity was observed in the paraventricular nucleus (PVN), supraoptic nucleus (SON), median preoptic area (MnPO), anterior hypothalamus (AH) and posterior hypothalamus (PH) of control (vehicle; n=6) and diabetic rats (Sprague–Dawley rats injected with STZ 65 mg/kg/ip 4 weeks prior to the experiment; n=6). Blood glucose levels were significantly elevated in the diabetic group (370±8 mg/dl) compared to control group (104±3 mg/dl). Diabetic rats had a significantly higher number of Fos-positive cells in PVN (2.5×), SON (7×) and MnPO (2×) compared to the control rats. However, diabetic rats had significantly fewer Fos-positive cells in the AH (0.3×) and no difference was observed in the PH between the diabetic and control rats. Despite the elevated number of Fos-positive cells in the diabetic rats, dehydration (water withdrawal for 24 h) or hypertonic challenge (1.5 ml of 0.1 M NaCl i.p. injection) produced a further increase in the number of Fos-positive cells in the PVN, SON and MnPO. Dehydration did not alter the number of Fos-positive cells in the AH or PH, but hypertonic challenge produced a significant increase in the Fos-positive cells in both the AH and PH of diabetic rats. This study demonstrates that: (1) there is increased basal neuronal activity in the PVN, SON and MnPO, a decrease in neuronal activity in the AH and no change in neuronal activity in the PH as indicated by Fos staining in diabetic rats; and (2) dehydration or hypertonic challenge produces a further increase in the number of Fos-positive cells in the PVN, SON, and MnPO which is comparable to control rats. These data support the conclusion that vasopressin producing neurons in the PVN and SON and autonomic areas within the lamina terminalis and hypothalamus are activated during diabetes and may contribute to the elevated levels of vasopressin and autonomic dysfunction during diabetes.

Noxious thermal stimulation of c-fos activity induced in rat lumbar spinal cord is reduced by AP-5 but not by Glycine

The effects of intrathecal administration of NMDA ( N-methyl- d-aspartic acid) receptor antagonist AP-5 (2-Amino-5-phosphonopentanoic acid), a competitive and specific NMDA antagonist, and glycine on the neuronal expression of c-fos protein (Fos) in the dorsal neurons lumbar segments four and five were studied after noxious heat stimulation. Heat (52°C, 3 s per application, repeated 10 times) was applied to the hindpaws of rats. NMDA receptor antagonist AP-5 (0.1 mmol/10 ml, i.t.) suppressed the noxious heat-induced Fos immunoreactivity by 65% as compared to animals pre-treated with saline. In contrast, glycine (0.1 μmol/10 μl, it.) did not influence Fos expression induced by the noxious heat stimulation. This study suggests that excitatory amino acids, e.g. glutamate but not the inhibitory aminos acid, glycine, plays a role in thermal nociception which in turn is mediated, in part, by c-fos activity.

Expression of c-fos protein in the medulla oblongata of conscious rabbits in response to baroreceptor activation

Neuronal expression of c-fos protein (Fos) in the medulla in response to baroreceptor activation was studied in conscious rabbits. Raising arterial pressure resulted in a marked increase, compared to control animals, in Fos immunoreactivity in the nucleus tractus solitarius, area postrema and ventrolateral medulla (VLM). Fos-immunoreactive neurons in the VLM extended from the level just rostral to the obex to 3 mm more caudal. Only a small proportion of these neurons showed tyrosine hydroxylase immunoreactivity. The results indicate that baroreceptor activation induces Fos expression in circumscribed medullary regions which have previously been shown to receive excitatory baroreceptor inputs.