Fos-related Antigen Immunoreactivity Research Articles

Renal sympathetic activation from long-term low-dose angiotensin II infusion in rabbits

Activation of renal sympathetic nerve activity (RSNA) has not been observed during long-term infusion of angiotensin II (AngII) which results in marked hypertension, despite activation of hypothalamic autonomic regions. We examined whether the function of central pathways influencing sympathetic activity is altered in conscious rabbits given a low dose of AngII that produces a modest hypertension and, therefore, limited secondary complications. Rabbits received AngII (20-30 ng/kg per min, subcutaneously) or sham treatment for 3 months at which time they were implanted with a renal sympathetic nerve electrode and the responses to airjet stress, baroreflexes and hypoxia were examined. AngII infusion for 3 months increased mean arterial pressure by 16% and RSNA by 43%. Increases in RSNA during airjet stress and hypoxia (10% O2) were 35 and 65% greater in AngII-treated rabbits than sham controls, respectively. Tachycardic responses were also enhanced. Baroreflexes were shifted to the right and upward in the AngII animals but baroreflex gain was similar in the two groups, indicating near complete resetting. Greater neuronal Fos-related antigen immunoreactivity was found in the vascular organ of the lamina terminalis, paraventricular and supraoptic hypothalamic nuclei in AngII-treated rabbits compared with sham. Our results suggest that low-dose AngII-treatment results in marked sympathetic activation at rest and during stress and hypoxia, due to activation of specific hypothalamic pathways. These mechanisms may contribute to sympathetic activation in conditions associated with chronic activation of the renin-angiotensin system such as obesity or renovascular disease.

Fos-Related Antigen Immunoreactivity After Acute and Chronic Angiotensin II–Induced Hypertension in the Rabbit Brain

Several brain regions are proposed as contributing to chronic sympatho-excitatory effects of elevated circulating angiotensin II. However, earlier c-Fos studies have been limited to acute angiotensin II exposure. This study aims to determine brain regions responding with chronic elevated angiotensin II. Rabbits were administered angiotensin II (50 ng/kg per minute) or saline for 3 hours, 3 days, or 14 days. Basal mean arterial pressure was 71+/-2 mm Hg and increased 23+/-2 mm Hg, 32+/-4 mm Hg, and 22+/-2 mm Hg for 3 hours, 3 days, and 14 days, respectively, with angiotensin II infusion. Neuronal activation was detected using Fos-related antigens, which recognizes all of the known members of the Fos family. Neurons located in the amygdala and area postrema were activated transiently after acute infusion of angiotensin II but were not responsive by days 3 or 14. Neurons located in the nucleus of the solitary tract, caudal ventrolateral medulla, and lateral parabrachial nucleus were activated for <or=3 days after infusion of angiotensin II but were not responsive by day 14, which is consistent with their role in response to baroreceptor pathways that reset with sustained hypertension. The vascular organ of the lamina terminalis and subfornical organ showed sustained but diminishing activation over the 14-day period. However, the downstream hypothalamic nuclei that receive inputs from these nuclei, the paraventricular, supraoptic, and arcuate nuclei, showed marked sustained activation. These findings suggest that there is desensitization of circumventricular organs but sensitization of neurons in hypothalamic regions to long-term angiotensin II infusion.

Ginsenosides attenuate methamphetamine-induced behavioral side effects in mice via activation of adenosine A 2A receptors: possible involvements of the striatal reduction in AP-1 DNA binding activity and proenkephalin gene expression

Current evidence suggests that ginsenosides inhibit methamphetamine (MA)-induced changes in behavior, but the precise mechanisms that underlie this effect are yet to be determined. We examined the role of adenosine receptors in the ginsenoside-induced changes in hyperlocomotion and conditioned place preference (CPP) in mice that occurred in response to administration of MA (2 mg/kg, i.p. × 1 or 2 mg/kg, i.p. × 6). Changes in circling behavior paralleled changes in CPP in the presence of MA. Pre-treatment with ginsenosides (50 or 150 mg/kg, i.p.) attenuated the MA-induced circling behavior and CPP. This attenuation was reversed by the adenosine A 2A receptor antagonist 1,3,7-trimethyl-8-(3-chrostyryl)xanthine (CSC; 0.5 and 1.0 mg/kg) in a dose-dependent manner, but neither the adenosine A 1 receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine (CPT; 0.5 and 1.0 mg/kg) nor the A 2B receptor antagonist alloxazine (ALX; 1.5 and 3.0 mg/kg) had any such effect. MA-induced increases in activator protein (AP)-1 DNA binding activity, Fos-related antigen immunoreactivity (FRA-IR), proenkephalin mRNA expression, and proenkephalin-like immunoreactivity were reduced consistently in the striatum of animals that were pretreated with ginsenosides. These reductions were largely prevented by CSC, but not by CPT or ALX. Our results suggest that the stimulation of A 2A receptors by ginsenosides attenuates the changes in behavior and the increases in AP-1 DNA binding activity, FRA-IR, and proenkephalin gene expression in mouse striatum that are induced by MA.

Attenuation of cocaine-induced conditioned place preference by Polygala tenuifolia root extract

A recent investigation indicated that Polygala tenuifolia Willdenow extract (PTE) possesses a potential antipsychotic effect. In this study, we examined the effects of PTE on the cocaine-induced changes in locomotor activity, conditioned place preference (CPP), fos-related antigen-immunoreactivity (FRA-IR), and activator protein (AP)-1 DNA binding activity. Cocaine-induced behavioral effects (hyperlocomotion and CPP) occurred in parallel with increases in FRA-IR and AP-1 DNA binding activity in the nucleus accumbens. These responses induced by cocaine were consistently attenuated by concurrent treatment with PTE (25 mg or 50 mg/kg/day, i.p. × 7). The adenosine A 2A receptor antagonist, 1,3,7-trimethyl-8-(3-chlorostyrl)xanthine (0.5 or 1.0 mg/kg, i.p.), reversed the PTE-mediated pharmacological action in a dose related manner; neither the adenosine A 1 receptor antagonist, 8-cyclopentyl-1,3-dimethylxanthine (0.5 or 1.0 mg/kg, i.p.) nor the A 2B receptor antagonist, alloxazine (1.5 or 3.0 mg/kg, i.p.) significantly affected this pharmacological action. Our results suggest that PTE prevents cocaine-induced behavioral effects, at least in part, via the activation of the adenosine A 2A receptor.

Selegiline potentiates the effects of EGb 761 in response to ischemic brain injury

We evaluated whether combined treatment with selegiline, a selective MAO-B inhibitor, and EGb 761, a standard extract of Ginkgo biloba, has synergistic effects against ischemic reperfusion injury (IRI) in gerbils. Interestingly, we observed that pretreatment with EGb 761 significantly attenuated selegiline-induced hyperactivity. This finding paralleled striatal fos-related antigen immunoreactivity (FRA-IR) in mice. Four minutes of bilateral carotid artery occlusion caused substantial cell loss in the CA1 of the hippocampus 5 days post-ischemic insult. Pretreatment with EGb 761, with or without selegiline, significantly attenuated this neuronal loss. Combined treatment with EGb 761 plus selegiline was more efficacious in preventing this loss. Synaptosomal formations of protein carbonyl, lipid peroxidation (malondialdehyde (MDA) + 4-hydroxyalkenal (4-HDA)), and reactive oxygen species (ROS) in the hippocampus remained elevated 5 days post-ischemic insult. The antioxidant effects appeared to be most significant in the group treated with EGb 761 plus selegiline. This combined treatment produced more significant attenuation of IRI-induced alterations in intramitochondrial calcium accumulation, the mitochondrial transmembrane potential, and mitochondrial Mn-superoxide dismutase-like immunoreactivity (Mn-SOD-IR) than either treatment alone. Our results suggest that co-administration of EGb 761 and selegiline produces significant neuroprotective effects via suppression of oxidative stress and mitochondrial dysfunction without affecting neurological function.

Dimemorfan prevents seizures induced by the L-type calcium channel activator BAY k-8644 in mice

A dextromethorphan (3-methoxy-17-methylmorphinan) analog, dimemorfan (3-methyl- N-methylmorphinan) that is not metabolized to dextrorphan [3-hydroxy-17-methylmorphinan, which induces phencyclidine (PCP)-like behavioral effects], attenuates maximal electroshock seizures. However, the pharmacological mechanism of action of dimemorfan remains to be determined. In this study, we assessed the locomotor activity mediated by these morphinans. Circling behavior was pronounced in mice treated with PCP or dextrorphan, while animals treated with dextromethorphan exhibited moderate behaviors. Dimemorfan did not show any significant behavioral effects. We used BAY k-8644 (an L-type Ca 2+ channel agonist in the dihydropyridine class) to explore the effects of dextromethorphan and dimemorfan on the convulsant activity regulated by calcium channels. Intracerebroventricular injection of BAY k-8644 (37.5 μg) significantly induced seizures in mice. As with dextromethorphan (6.25 or 12.5 mg/kg), dimemorfan (6.25 or 12.5 mg/kg) pretreatment significantly attenuated BAY k-8644-induced seizures in a dose-dependent manner. BAY k-8644-induced seizure activity paralleled increased expression of c- fos and c- jun, AP-1 DNA binding activity, and fos-related antigen immunoreactivity. Pretreatment with dextromethorphan or dimemorfan significantly attenuated the expression induced by BAY k-8644. Therefore, our results suggest that the anticonvulsant effects of dextromethorphan and dimemorfan are mediated, at least in part, via L-type calcium channel, and that dimemorfan is equipotent to dextromethorphan in preventing BAY k-8644-induced seizures, while it lacks behavioral side effects related to psychotomimetic reactions.

Acute sodium deficit triggers plasticity of the brain angiotensin type 1 receptors.

The brain renin-angiotensin system (bRAS) is involved in the control of hydromineral balance. However, little information is available on the functional regulation of the bRAS as a consequence of sodium deficit in the extracellular fluid compartments. We used a pharmacological model of acute Na+ depletion (furosemide injections) to investigate changes of a major component of the bRAS, the hypothalamic angiotensin type 1A (AT(1A)) receptors. Furosemide induced a rapid and long-lasting expression of the AT(1A) mRNA in the subfornical organ, the median preoptic nucleus (MnPO), and the parvocellular division of the paraventricular nucleus (pPVN). Na+ depletion increased the number of cells expressing AT(1A) mRNA in the pPVN, but not in the MnPO. The enhancement of AT(1A) mRNA expression was associated with an increase in AT(1) binding sites in all the regions studied. It is of interest that in the paraventricular nucleus, the majority of the neurons expressing AT(1A) mRNA also showed an increase in metabolic activity (Fos-related antigen immunoreactivity [FRA-ir]). By contrast, in the MnPO, we observe two distinct cell populations. Our data demonstrated that an acute Na+ deficit induced a functional regulation of the hypothalamic AT(1A) receptors, indicating that these receptors are subject to plasticity in response to hydromineral perturbations.

Carbetapentane attenuates kainate-induced seizures via σ-1 receptor modulation

We examined the effects of a non-opioid antitussive, carbetapentane (CB) on kainic acid (KA)-induced neurotoxicity in rats. KA administration (10 mg/kg, i.p.) produced robust behavioral convulsions lasting 4 to 5 h. CB (12.5 and 25 mg/kg, i.p.) pretreatment consistently and in a dose-dependent manner reduced the KA-induced seizures, mortality, and marked loss of cells in regions CA1 and CA3 of the hippocampus. Consistently, CB pretreatment also significantly attenuated the KA-induced increase in Fos-related antigen immunoreactivity in the hippocampus. In contrast, pretreatment with the σ-1 receptor antagonist BD1047 (1 and 2 mg/kg, i.p.) blocked, in a dose-related manner, the neuroprotection afforded by CB. These results suggest that CB provides neuroprotection against KA insult via σ-1 receptor modulation.

Dextromethorphan affects cocaine-mediated behavioral pattern in parallel with a long-lasting Fos-related antigen-immunoreactivity

In order to understand the underlying mechanisms responsible for the behaviors mediated by dextromethorphan (DM), we examined the effects of DM on locomotor activity and locomotor patterns in mice, and Fos-related antigen immunoreactivity (FRA-IR) of mouse brain following repeated administration of cocaine. Combined treatments (30 min prior to each cocaine administration) with DM dose-dependently decreased locomotor activity for high doses of cocaine (20 mg/kg, i.p./day × 7). DM combinations did not significantly affect hyperactivity for 10 mg cocaine/kg, i.p./day × 7. In contrast, combined treatments with DM increased the locomotor activity for 5 mg cocaine/kg, i.p./day × 7. These results were consistent with alterations in marginal activity. Repeated administration with cocaine or DM increased FRA-IR in the nucleus accumbens (NAc) and striatum which lasted for at least 7 days. Our results suggest that DM exhibits biphasic effects on the locomotor stimulation induced by cocaine, and that locomotor activities are in parallel with FRA-IR of the striatal complex. However, the role of FRA-IR regulated by DM or/and cocaine remains to be further determined.

Dual effects of dextromethorphan on cocaine-induced conditioned place preference in mice

Dextromethorphan (DM) at supra-antitussive doses might produce psychotomimetic effects in humans. In order to understand the underlying mechanisms responsible for the behavior induced by DM, we examined the effects of DM on cocaine-induced conditioned place preference (CPP) and locomotor pattern in mice, and Fos-related antigen immunoreactivity (FRA-IR) in the striatal complex (nucleus accumbens and striatum) of the mouse brain. The effects of DM (20 and 40 mg/kg, i.p.) on the CPP for 2.5, 5, 10, and 20 mg cocaine/kg, i.p. were assessed. Pretreatment with DM dose-dependently decreased the CPP for 20 mg cocaine/kg. Similarly, pretreatment with DM appeared to reduce the CPP for 10 mg cocaine/kg, but increase the CPP for 5 mg cocaine/kg. This finding was more pronounced for 2.5 mg cocaine/kg; DM significantly increased the CPP for 2.5 mg cocaine/kg in a dose-related manner. Furthermore, these results were correlated with alterations in the locomotor pattern (marginal activity) and FRA-IR in the striatal complex. Thus, our results suggest that DM exhibits a biphasic effect on the cocaine-induced CPP and locomotor pattern.

Prolonged exposure to cigarette smoke blocks the neurotoxicity induced by kainic acid in rats

We examined the effects of cigarette smoke (CS) on three parameters associated with kainic acid (KA)-induced neurotoxicity: seizure activity, cell loss in the hippocampus, and increased Fos-related antigen (FRA) expression. Animals were exposed to the main stream of CS from 15 Kentucky 2R1F research cigarettes containing 28.6 mg tar and 1.74 mg nicotine per cigarette, for 10 min a day, 6 days per week, for 4 weeks, using an automatic smoking machine. KA administration (10 mg kg , i.p.) produced robust behavioral convulsions lasting 4–5 h. Pre-exposure to CS significantly reduced the seizures, mortality, and severe loss of cells in regions CA1 and CA3 of the hippocampus after KA administration. Consistently, pre-exposure to CS significantly attenuated the KA-induced increased FRA immunoreactivity in the hippocampus. In contrast, pretreatment with central nicotinic antagonist, mecamylamine (2 or 10 mg kg , i.p.) blocked the neuroprotective effects mediated by CS in a dose-dependent manner. These results indicate that CS exposure provides neuroprotection against the KA insult via nicotinic receptor activation.

Feedback effects of placental lactogens on prolactin levels and Fos-related antigen immunoreactivity of tuberoinfundibular dopaminergic neurons in the arcuate nucleus during pregnancy in the rat.

PRL in the rat exerts its luteotropic action during the first half of pregnancy. After midpregnancy, placental lactogens (PLs) take the place of PRL to stimulate progesterone secretion from the corpus luteum. Simultaneously, PLs trigger a negative feedback on PRL secretion. However, the brain mechanisms for the negative feedback induced by PLs are not fully understood. Here, we report changes in plasma PRL levels, tuberoinfundibular dopaminergic (TIDA) neuronal activity as measured by Fos-related antigen (FRA)/tyrosine hydroxylase (TH) immunoreactivity, and TH catalytic activity as measured by dihydroxyphenylalanine (DOPA) accumulation in the stalk-median eminence (SME) after experimental manipulation of PL levels. On day 4 of pregnancy, animals received Rcho-1 cells intracerebroventricularly (i.c.v.) to increase the level of PLs in the brain or HRP-1 cells as controls. On day 12 of pregnancy, hysterectomy alone or i.c.v. HRP-1 injection plus hysterectomy were performed to remove the source of PLs. Rcho-1 i.c.v. injection plus hysterectomy were performed to examine the effect of replacement of the PL source. Sham-hysterectomized animals were used as a control group. Animals were killed 2 days after each treatment at 0200 and 1800 h, which represent the peak times of PRL surges, and at 1400 h, which represents the intersurge time, by either transcardial perfusion for FRA/TH immunocytochemistry or decapitation 30 min after NSD 1015 injection to assess DOPA accumulation with HPLC-electrochemical detection. Rcho-1 cells completely abolished PRL surges on day 6 of pregnancy and increased the percentage of FRA/TH immunoreactivity in the dorsomedial, ventrolateral, and caudal subdivisions of the arcuate nucleus. This change in neuronal activity reflected the amount of DOPA accumulation in the SME, which was high at all time points. On day 14 of pregnancy, removal of the PL source by hysterectomy resulted in increased PRL levels and decreased neuronal activity of TIDA neurons at all three time points. Similar profiles were observed in animals that received i.c.v. HRP-1 injection plus hysterectomy. Replacement of the source of PL with Rcho-1 cells in hysterectomized rats resulted in low PRL secretion, high neuronal activity of TIDA neurons, and high TH catalytic activity. These patterns were the same as those in sham-operated animals. Our results demonstrate that PLs induce an increase in the neuronal activity of dopaminergic neurons, as measured by FRA/TH immunoreactivity and TH catalytic activity in the SME. Removal of the PL source elevates plasma PRL levels at all times during the second half of pregnancy and does not restore PRL surges.

Feedback Effects of Placental Lactogens on Prolactin Levels and Fos-Related Antigen Immunoreactivity of Tuberoinfundibular Dopaminergic Neurons in the Arcuate Nucleus during Pregnancy in the Rat

Feedback Effects of Placental Lactogens on Prolactin Levels and Fos-Related Antigen Immunoreactivity of Tuberoinfundibular Dopaminergic Neurons in the Arcuate Nucleus during Pregnancy in the Rat

Repeated amphetamine administration induces a prolonged augmentation of phosphorylated cyclase response element-binding protein and Fos-related antigen immunoreactivity in rat striatum

Semi-quantitative immunocytochemistry was used to investigate the levels of cyclase response element-binding protein, phosphorylated cyclase response element-binding protein, Fos and Fos-related antigen immunoreactivity in the striatum of rats after acute or repeated amphetamine administration. Rats were perfused 20 min (phosphorylated cyclase response element-binding protein) or 2 h (cyclase response element-binding protein, phosphorylated cyclase response element-binding protein, Fos, Fos-related antigen) after a single injection (5 mg/kg, i.p.) or five daily injections of amphetamine. The latency to onset of stereotypical behaviors was significantly reduced in rats exposed to repeated amphetamine as compared to acute amphetamine, indicating development of behavioral sensitization. Cyclase response element-binding protein immunoreactivity was not altered in the dorsal or ventral striatum following acute or repeated amphetamine. Phosphorylated cyclase response element-binding protein immunoreactivity was significantly induced 20 min, but not 2 h, following acute amphetamine, whereas a significant induction of phosphorylated cyclase response element-binding protein immunoreactivity was found 20 min and 2 h after repeated amphetamine in the dorsal striatum only. Fos immunoreactivity was significantly induced in the dorsal striatum following acute and repeated amphetamine. Fos immunoreactivity in the core of the nucleus accumbens was significantly increased following repeated amphetamine only. Acute amphetamine induced, and repeated amphetamine further augmented, Fos-related antigen immunoreactivity in the dorsal striatum, while not affecting Fos-related antigen immunoreactivity in the nucleus accumbens. These data demonstrate that repeated amphetamine administration results in a prolonged induction of phosphorylated cyclase response element-binding protein and Fos-related antigen immunoreactivity in the dorsal striatum, indicating that alterations in striatal gene expression associated with the development of behavioral sensitization may be mediated, in part, by these transcription factors.

Kainate‐Induced Changes in Opioid Peptide Genes and AP‐1 Protein Expression in the Rat Hippocampus

In the rat hippocampus, jun, c-fos, and fos-related antigen immunoreactivity, AP-1 DNA binding, and opioid peptide gene expression were examined after kainate treatment to determine whether the induction and DNA binding of AP-1 transcription factors are correlated with the expression of the opioid peptide genes. One and one-half hours after kainate administration, fos-related antigen and jun immunoreactivity and AP-1 DNA binding were induced; maximal elevation was observed after 4.5 h. Transcription factor expression and DNA binding increased in a dose-dependent manner. Preprodynorphin and preproenkephalin mRNA induction was also dose dependent. The anticonvulsants, pentobarbital and diazepam, effectively blocked electroencephalographic seizure activity caused by kainate treatment, whereas valproic acid was approximately 50% effective. Opioid peptide gene expression, fos-related antigen and jun immunoreactivity, and AP-1 DNA binding all reflected similar reductions after anticonvulsant treatment. Therefore, expression and DNA binding activity of the AP-1 transcription factors are correlated with opioid peptide gene expression in the rat hippocampus.