Atypical antipsychotic properties of AD-6048, a primary metabolite of blonanserin.

Blonanserin is a new atypical antipsychotic drug that shows high affinities to dopamine D2 and 5-HT2 receptors; however, the mechanisms underlying its atypicality are not fully understood. In this study, we evaluated the antipsychotic properties of AD-6048, a primary metabolite of blonanserin, to determine if it contributes to the atypicality of blonanserin. Subcutaneous administration of AD-6048 (0.3-1mg/kg) significantly inhibited apomorphine (APO)-induced climbing behavior with an ED50 value of 0.200mg/kg, the potency being 1/3-1/5 times that of haloperidol (HAL). AD-6048 did not cause extrapyramidal side effects (EPS) even at high doses (up to 10mg/kg, s.c.), whereas HAL at doses of 0.1-3mg/kg (s.c.) significantly induced bradykinesia and catalepsy in a dose-dependent manner. Thus, the therapeutic index (potency ratios of anti-APO action to that of EPS induction) of AD-6048 was much higher than that of haloperidol, illustrating that AD-6048 per se possesses atypical antipsychotic properties. In addition, immunohistochemical analysis of Fos protein expression revealed that both AD-6048 and HAL significantly increased Fos expression in the shell part of the nucleus accumbens and the striatum. However, in contrast to HAL which preferentially enhanced striatal Fos expression, AD-6048 showed a preferential action to the nucleus accumbens. These results indicate that AD-6048 acts as an atypical antipsychotic, which seems to at least partly contribute to the atypicality of blonanserin.

Tooth movement activates the central amygdala and the lateral hypothalamus by the magnitude of the force applied.

OBJECTIVE: To determine if the magnitude of the force used to induce incisor tooth movement promotes distinct activation in cells in the central amygdala (CEA) and lateral hypothalamus (LH) of rats. Also, the effect of morphine on Fos immunoreactivity (Fos-IR) was investigated in these nuclei. MATERIALS AND METHODS: Adult male rats were anesthetized and divided into six groups: only anesthetized (control), without orthodontic appliance (OA), OA but without force, OA activated with 30g or 70g, OA with 70g in animals pretreated with morphine (2 mg/kg, intraperitoneal). Three hours after the onset of the experiment the rats were reanesthetized and perfused with 4% paraformaldehyde. The brains were removed and fixed, and sections containing CEA and LH were processed for Fos protein immunohistochemistry. RESULTS: The results show that in the control group, the intramuscular injection of a ketamine/ xylazine mixture did not induce Fos-IR cells in the CEA or in the LH. Again, the without force group showed a little Fos-IR. However, in the 70g group the Fos-IR was the biggest observed (P < .05, Tukey) in the CEA and LH compared with the other groups. In the 30g group, the Fos-IR did not differ from the control group, the without OA group, and the without force group. Furthermore, pretreatment with morphine in the 70g group reduced Fos-IR in these regions. CONCLUSIONS: Tooth movement promotes Fos-IR in the CEA and LH according to the magnitude of the force applied.

Repeated amphetamine administration outside the home cage enhances drug-induced Fos expression in rat nucleus accumbens.

Induction of the immediate early gene protein product Fos has been used extensively to assess neural activation in the striatum after repeated amphetamine administration to rats in their home cages. However, this technique has not been used to examine striatal activation after repeated administration outside the home cage, an environment where repeated drug administration produces more robust psychomotor sensitization. We determined the dose-response relationship for amphetamine-induced psychomotor activity and Fos expression in nucleus accumbens and caudate-putamen 1 week after repeated administration of amphetamine or saline in locomotor activity chambers. Repeated administration of amphetamine enhanced amphetamine-induced locomotor activity and stereotypy and Fos expression in nucleus accumbens, but not in caudate-putamen. In comparison, levels of Fos expression induced by 1mg/kg amphetamine were not altered in nucleus accumbens or caudate-putamen by repeated amphetamine administration in the home cage. Double-labeling of Fos protein and enkephalin mRNA indicates that Fos is expressed in approximately equal numbers of enkephalin-negative and enkephalin-positive neurons in nucleus accumbens and caudate-putamen following injections outside the home cage. Furthermore, repeated amphetamine administration increased drug-induced Fos expression in enkephalin-positive, but not enkephalin-negative, neurons in nucleus accumbens. We conclude that repeated amphetamine administration outside the home cage recruits the activation of enkephalin-containing nucleus accumbens neurons during sensitized amphetamine-induced psychomotor activity.

Parthenolide is the component of tanacetum parthenium that inhibits nitroglycerin-induced Fos activation: studies in an animal model of migraine.

Tanacetum parthenium (TP) is a member of the Asteracee family long used empirically as a herbal remedy for migraine. So far, however, clinical trials have failed to prove consistently the effectiveness of TP extracts in preventing migraine attacks, probably as a consequence of the uncertainty as regards the active principle. In this study, the biological effects of different TP extracts and purified parthenolide were tested in an animal model of migraine based on the quantification of neuronal activation induced by nitroglycerin. The extract enriched in parthenolide significantly reduced nitroglycerin-induced Fos expression in the nucleus trigeminalis caudalis. Purified parthenolide inhibited nitroglycerin-induced neuronal activation in additional brain nuclei and, significantly, the activity of nuclear factor-kappaB. These findings strongly suggest that parthenolide is the component responsible for the biological activity of TP as regards its antimigraine effect and provide important information for future controlled clinical trials.

Enhanced cardiovascular alteration and Fos expression induced by central salt loading in a conscious rat transgenic for the metallothionein-vasopressin fusion gene.

The present study is an investigation of the responses of the cardiovascular system and Fos expression to intracerebroventricular (i.c.v.) administration of hypertonic saline (HS) in conscious arginine vasopressin (AVP)-overexpressing transgenic (Tg) and control rats. Central HS (0.3, 0.67, or 1.0M NaCl, 1 microl/min for 20 min) significantly increased the mean arterial blood pressure (MABP) and Fos-like immunoreactivity (FLI) in the paraventricular nucleus (PVN) and supraoptic nucleus (SON) of the hypothalamus, the area postrema (AP), the median preoptic nucleus (MnPO), and the organum vasculosum laminae terminalis (OVLT) in both Tg and control rats. The changes in MABP and FLI were significantly larger in Tg rats than in control rats. i.c.v. pretreatment with the AVP V1 receptor antagonist, OPC-21268, blocked the increase in MABP and significantly decreased the Fos expression in the PVN (posterior magnocellular (pm) component) induced by 0.3 M HS in the Tg rats. The present study demonstrates an increased responsiveness to i.c.v. administration of HS in AVP Tg rats, suggesting the relationship between the vasopressinergic drive and central cardiovascular response via, at least in part, the V1 receptor in the PVN magnocellular neurons.

The contribution of peripheral 5-hydroxytryptamine2A receptor to carrageenan-evoked hyperalgesia, inflammation and spinal Fos protein expression in the rat.

The present study was conducted to test the hypothesis that the peripheral 5-hydroxytryptamine (5-HT)2A receptor is involved in inflammatory hyperalgesia and production of noxious stimulus-induced neuronal activity at the level of the spinal cord dorsal horn. Intraplantar (i.pl.) injection of carrageenan dramatically reduced paw withdrawal latency to noxious heat (47 degrees C) and caused paw swelling. Pretreatment with ketanserin, a selective antagonist of 5-HT2A receptor, in the hindpaw produced dose-dependent inhibition of the hyperalgesia (0.5, 3 and 5 mug; i.pl.) with full relief at 5 mug. The drug also moderately reduced carrageenan-induced paw swelling in a dose-dependent manner. Carrageenan induced conspicuous expression of c-fos-like immunoreactivity (FLI) in the spinal dorsal horn of segments L4-5. Ketanserin (5 mug) markedly reduced carrageenan-induced FLI in all laminae of the dorsal horn. However, blockade of peripheral 5-HT1A receptors by (N-2-[4-(2-methoxyphenyl-1-piperazinyl] ethyl]-N-2-pyridinylcyclohexanecarboxamide at maximally effective doses (30 and 100 mug; i.pl.) did not alter carrageenan-induced hyperalgesia, edema or expression of FLI. The present study provided evidence at cellular level that the peripheral 5-HT2A receptor is preferentially involved in the development of thermal hyperalgesia in the carrageenan model of inflammation.

Effects of isoflurane on prefrontal acetylcholine release and hypothalamic Fos response in young adult and aged rats.

This experiment investigated the influence of age on prefrontal acetylcholine (ACh) release and Fos response in the hypothalamic paraventricular nucleus and the nucleus tractus solitarius (NTS) of rats following isoflurane anesthesia. It is known that isoflurane decreases acetylcholine release in most brain regions. In the present study, we found that the level of prefrontal acetylcholine was significantly lower in 28-month-old rats (14% of baseline) than in 3-month-old rats (38% of baseline) during 2 h of isoflurane anesthesia (P < 0.05). The old rat group showed significantly greater Fos induction in the paraventricular nucleus compared to the young adult rat group (P < 0.05), indicating that the old rats were subjected to stress. No difference in Fos response was noted in the nucleus tractus solitarius. The old rats displayed a significant increase in feeding behavior during the 3-h recovery period (P < 0.05), but there was no difference in overall acetylcholine levels. Taken together, these findings suggest that isoflurane anesthesia influences old rats more profoundly than young adult rats with regard to reductions in acetylcholine release and stress responses. This may have implications for understanding the development of postoperative delirium in aged patients.

Mineralocorticoid treatment upregulates the hypothalamic vasopressinergic system of spontaneously hypertensive rats.

Mineralocorticoid effects in the brain include the control of cardiovascular functions, induction of salt appetite, interaction with the vasoactive neuropeptides arginine vasopressin (AVP) and angiotensin II and development or aggravation of hypertension. In this regard, mineralocorticoids may play a pathogenic role in rats with a genetic form of hypertension (spontaneously hypertensive rats, SHR). Our objective was to compare the response of the hypothalamic vasopressinergic system to mineralocorticoid administration in SHR and control Wistar-Kyoto (WKY) rats. Sixteen-week-old male SHR showing a systolic blood pressure of 190 +/- 5 mm Hg and normotensive WKY rats (130 +/- 5 mm Hg) were treated subcutaneously with oil vehicle or a single 10-mg dose of deoxycorticosterone acetate (DOCA). After 2 h, rats were sacrificed and brains prepared for immunocytochemistry of Fos and vasopressin V1a receptor (V1aR) and for non-isotopic in situ hybridization of AVP mRNA. In the basal state, SHR demonstrated a higher number of AVP mRNA- and V1aR-immunopositive cells in the magnocellular division of the paraventricular hypothalamic nucleus (PVN) than WKY rats. After DOCA injection, SHR responded with a significant increase in both parameters with respect to vehicle-injected SHR. In WKY rats, DOCA was without effect on AVP mRNA although it increased the number of V1aR-positive cells. Changes in the number of Fos-positive nuclei were measured in the PVN, median preoptic nucleus (MnPO) and organum vasculosum of the lamina terminalis (OVLT), a circumventricular region showing anatomical connections with the PVN. In vehicle-injected rats, the PVN of SHR showed a higher number of Fos-positive nuclei than in WKY rats, whereas after DOCA treatment, a significant increment occurred in the OVLT but not in the PVN or MnPO of the SHR group only. These data suggest that the enhanced response of the vasopressinergic system to mineralocorticoids may contribute to the abnormal blood pressure of SHR.

Peripheral secretin-induced Fos expression in the rat brain is largely vagal dependent.

I.v. injection of secretin activates neurons in brain areas controlling autonomic function and emotion. Peripheral administration of secretin inhibits gastric functions through a central mechanism that is mediated by vagal dependent pathways. We investigated whether the vagus nerve is involved in i.p. injection of secretin-induced brain neuronal activation in conscious rats as monitored by Fos immunohistochemistry. Secretin (40 or 100 microg/kg, i.p., 90 min) induced a dose-related increase in the number of Fos positive neurons in the central nucleus of the amygdala (CeA), and a plateau Fos response in the area postrema (AP), nucleus tractus solitarii (NTS), locus coeruleus (LC), Barrington's nucleus (Bar), external lateral subnucleus of parabrachial nucleus (PBel) and arcuate nucleus, and at 100 microg/kg, in the dorsal motor nucleus of the vagus (DMV) compared with i.p. injection of vehicle. Double immunohistochemistry showed that secretin (40 microg/kg, i.p.) activates tyrosine hydroxylase neurons in the NTS. Subdiaphragmatic vagotomy (7 days) abolished Fos expression-induced by i.p. secretin (40 microg/kg) in the NTS, DMV, LC, Bar, PBel and CeA, while a significant rise in the AP was maintained. In contrast, s.c. capsaicin (10 days) did not influence the Fos induction in the above nuclei. Reverse transcription polymerase chain reaction (RT-PCR) and quantitative real-time PCR showed that secretin receptor mRNA is expressed in the nodose ganglia and levels were higher in the right compared with the left ganglion. These results indicate that peripheral secretin activates catecholaminergic NTS neurons as well as neurons in medullary, pontine and limbic nuclei regulating autonomic functions and emotion through vagal-dependent capsaicin-resistant pathways. Secretin injected i.p. may signal to the brain by interacting with secretin receptors on vagal afferent as well as on AP neurons outside the blood-brain barrier.

Excessive testosterone treatment and castration induce reactive astrocytes and fos immunoreactivity in suprachiasmatic nucleus of mice.

The suprachiasmatic nucleus (SCN) has long been recognized as the central mammalian circadian pacemaker that controls behavioral and physiological processes. The role of the SCN in circadian rhythms has been the subject of a wide range of physiological and behavioral studies, although the influence of homeostasis rhythms (such as fluctuating hormone levels) on the SCN of the hypothalamus is not entirely clear. The present study was undertaken to examine the morphological interactions between astroglial and neuronal elements in the SCN of mice after either a short-term excessive testosterone treatment (ETT) or castration, using glial fibrillary acidic protein (GFAP), and immediate early gene c-fos as well as calbindin-D28k (CB) immunohistochemistry. Both ETT and castration resulted in a significant increase in the accumulation of reactive astrocytes and Fos-imunoreactivity (IR), especially in the dorsomedial (DM) sub-region of the SCN. However, CB-IR neurons in the examined brain regions showed little change. These findings indicate that the DM sub-region of the SCN may be a possible center of hormonal regulation via a hypothalamic neuroendocrine circuit, and that a non-photic stimuli mechanism might play a role in circadian rhythm regulation.

Effects of gustatory nerve transection and regeneration on quinine-stimulated Fos-like immunoreactivity in the parabrachial nucleus of the rat.

The distribution of quinine-stimulated Fos-like immunoreactivity (FLI) in several subdivisions of the parabrachial nucleus (PBN) known to be responsive to gustatory stimulation was examined in rats in which the chorda tympani nerve (CT) and/or glossopharyngeal nerve (GL) was transected (Experiment 1) and in rats in which the GL was transected with regeneration promoted or prevented (Experiment 2). We confirmed previous findings in the literature by demonstrating that rats intraorally infused with 3 mM quinine showed a robust population of FLI in the waist area and the external lateral (EL) and external medial (EM) subdivisions of the PBN (Yamamoto et al. [1994] Physiol Behav 56:1197-1202; Travers et al., [ 1999] Am J Physiol 277:R384-R394). In the waist area, only GL transection significantly decreased the number of FLI-neurons elicited by intraoral infusion of quinine compared with water-stimulated controls. In the external subdivisions neither neurotomy affected the number of FLI-neurons. The effect of GL transection in the waist area was enduring for rats in which the GL did not regenerate (up to 94 days), but regeneration of the GL after 52 days restored quinine-stimulated FLI to control values. In these same GL-transected animals, there were parallel decreases in the number of gapes elicited by intraoral quinine stimulation that recovered, but only subsequent to regeneration of the GL. These data provide support for the role of the waist area in the brainstem processing that underlies oromotor rejection behaviors and also help substantiate the hypothesis that the CT and GL are relatively specialized with regard to function. Moreover, when the quinine-induced pattern of neural activity in the second central gustatory relay, as assessed by FLI, is substantially altered by the loss of peripheral gustatory input from the GL, it can be restored upon regeneration of the nerve.

Systemic apomorphine alters HPA axis responses to interleukin-1 beta administration but not sound stress.

Apomorphine is a dopamine receptor agonist that was recently licensed for the treatment of erectile dysfunction. However, although sexual activity can be stressful, there has been little investigation into whether treatments for erectile dysfunction affect stress responses. We have examined whether a single dose of apomorphine, sufficient to produce penile erections (50 microg/kg, i.a.), can alter basal or stress-induced plasma ACTH levels, or activity of central pathways thought to control the hypothalamic-pituitary-adrenal axis in rats. An immune challenge (interleukin-1 beta, 1 microg/kg, i.a.) was used as a physical stressor while sound stress (100 dB white noise, 30 min) was used as a psychological stressor. Intravascular administration of apomorphine had no effect on basal ACTH levels but did substantially increase the number of Fos-positive amygdala and nucleus tractus solitarius catecholamine cells. Administration of apomorphine prior to immune challenge augmented the normal ACTH response to this stressor at 90 min and there was a corresponding increase in the number of Fos-positive paraventricular nucleus corticotropin-releasing factor cells, paraventricular nucleus oxytocin cells and nucleus tractus solitarius catecholamine cells. However, apomorphine treatment did not alter ACTH or Fos responses to sound stress. These data suggest that erection-inducing levels of apomorphine interfere with hypothalamic-pituitary-adrenal axis inhibitory feedback mechanisms in response to a physical stressor, but have no effect on the response to a psychological stressor. Consequently, it is likely that apomorphine acts on a hypothalamic-pituitary-adrenal axis control pathway that is unique to physical stressors. A candidate for this site of action is the nucleus tractus solitarius catecholamine cell population and, in particular, A2 noradrenergic neurons.

Fos protein expression following acute administration of diethyldithiocarbamate in rats.

Dithiocarbamates are compounds commonly used in medicine and in agriculture and their prolonged use is known to result in neurotoxicity. Whether this response may be related to early gene expression has not been investigated. We have addressed this issue by mapping Fos expression in rats acutely injected with diethyldithiocarbamate (DDTC) and correlating these data to neural damage in the hippocampus as determined by pyknotic nuclei count. In comparison to saline injected rats, DDTC treatment induced a marked Fos expression in most brain regions at 1 and 3 h. In the hippocampus, a high Fos expression was followed by a variable number of pyknotic nuclei at 6 h, depending on the subregion. The data suggest that, in this model of neurotoxicity, c-fos induction does not reflect a cell commitment to die or survive, but rather a cell response to the DDTC-induced oxidative disorder.

Kynurenic acid enhances electroacupuncture analgesia in normal and carrageenan-injected rats.

The interaction between electroacupuncture (EA) and an intrathecally administered wide-spectrum excitatory amino acid (EAA) receptor(s) antagonist, kynurenic acid (KYNA) on carrageenan-induced thermal hyperalgesia and spinal Fos expression was investigated. Intrathecal (i.t.) injection of 0.1, 1, 10, and 100 nmol KYNA markedly and dose-dependently increased the latency of paw withdrawal (PWL) of the carrageenan-injected paw. While the PWLs of the non-injected and normal saline (NS)-injected paws were not obviously affected by application of KYNA at the doses tested. Intrathecal injection of 0.1 nmol KYNA significantly potentiated the anti-nociception induced by EA stimulation of contralateral 'Zu-San-Li' and 'Kun-Lun' acupoints either in the carrageenan- or NS-injected rats. Three hours after intraplantar (i.pl.) injection of carrageenan, the number of Fos-like immunoreactive (Fos-LI) neurons was significantly increased in all layers of ipsilateral spinal cord at L(4)-L(5) with the higher density in laminae I-II and V-VI. Intrathecally pre-administered KYNA (10 nmol) significantly reduced the total number of carrageenan-induced Fos-LI neurons with more apparent reduction in laminae I-II and IV-V. Pre-coapplication of 10 nmol KYNA and EA of bilateral 'Zu-San-Li' and 'Kun-Lun' acupoints, the numbers of carrageenan-induced Fos-LI neurons in laminae I-II and V-VI further reduced. The level of Fos expression in the spinal cord induced by carrageenan was significantly lower compared with that of i.t. injection of KYNA or EA alone. These results demonstrated that EAA receptor(s) antagonist could enhance EA-induced anti-nociception and anti-hyperalgesia.

Comparison of Fos induced in rat brain by GLP-1 and amylin.

The patterns of Fos-like immunoreactivity (Fos-ir) in rat brain were compared following treatment of rats with two anorectic 'gut' peptides. Central administration of GLP-1 produced dose-related increases in Fos-ir in the area postrema (AP) and caudal nucleus of the solitary tract (cNTS) as well as strong activation in the lateral parabrachial nucleus (LPBE), hypothalamic paraventricular nucleus (PVN), bed nucleus of the stria terminalis (BNST) and central nucleus of the amygdala (CeA). At centrally-active doses, peripheral administration of GLP-1 did not induce Fos-ir in brain. In contrast, peripheral administration of amylin produced strong Fos-ir in the AP and cNTS, as well as the BNST and CeA, but not in the PVN. The common activation of the LPB-BNST-CeA by these and other previously-studied anorectics suggest this is an important circuit involved in satiety.

Light-induced phase shifts and Fos expression in the hamster circadian system: the effects of anesthetics.

In the present study, we examined the effect of administration of anesthetics on light-induced phase shifts of the circadian system. This information is of critical importance, because many studies of light input to the mammalian suprachiasmatic nucleus (SCN) have been performed on anesthetized animals. We found that light-induced phase shifts were blocked by all drugs used at anesthetic doses. We then determined the effect of two of these agents on light induction of Fos-like immunoreactivity in the SCN. We found that the administration of sodium pentobarbital prevented light induction of Fos expression in the SCN, whereas the administration of urethane did not. These results raise cautions about the use of anesthetized animals to answer questions about the photic regulation of neuronal activity in the SCN.

Cisplatin resistance in human cancers.

Cancer chemotherapeutic agents primarily act by damaging cellular DNA directly or indirectly. Tumor cells, in contrast to normal cells, respond to cisplatin with transient gene expression to protect and/or repair their chromosomes. Repeated cisplatin treatments results in a stable resistant cell line with enhanced gene expression but lacking gene amplification for the proteins that will limit cisplatin cytotoxicity. Recently, several new human cell lines have been characterized for cisplatin resistance. These cell lines have led to a better understanding of the molecular and biochemical basis of cisplatin resistance. The c-fos proto-oncogene, a master switch for turning on other genes in response to a wide range of stimuli, has been shown to play an important role in cisplatin resistance both in vitro and in patients. Based on these studies, new strategies have been developed to circumvent and/or exploit clinical cisplatin resistance.