围绕两轴进行复杂的旋转刺激后大鼠全脑内Fos的表达(英文)

为了探讨旋转刺激与运动病发生的关系,本研究利用一种复杂的围绕两轴旋转的加速度刺激器刺激大鼠后,观察大鼠全脑内Fos蛋白的表达情况。动物被随机地分成四组,即正常对照组、两轴旋转刺激组、双侧迷路毁损组以及双侧迷路毁损后接受旋转刺激组。采用免疫组织化学染色方法观察全脑不同核团内Fos蛋白的表达情况。结果显示:(1)正常对照组和双侧迷路毁损组大鼠的脑内均未检测到Fos样免疫阳性产物;(2)两轴旋转刺激组的大鼠在给予复杂的围绕两轴旋转的加速度刺激后,在大鼠脑和脑干的多个核团内均可检测到Fos样免疫阳性神经元,其阳性产物主要表达于细胞核。其中在脑干内的前庭复合体的不同亚核(包括前庭内侧核、前庭上核和前庭下核),孤束核、蓝斑核、臂旁内侧核、臂旁外侧核,间脑的室旁核以及边缘系统的杏仁核等内均可观察到密集分布的Fos样免疫阳性神经元;(3)双侧迷路毁损组大鼠在接受复杂的围绕两轴旋转刺激后,在上述相应核团内均难以检测到Fos蛋白的表达。以上研究结果提示两轴旋转刺激可以有效地激活前庭神经元,而大鼠在接受前庭刺激后,脑和脑干的许多核团内大量的神经元可能通过与前庭核复合体发生直接或间接的纤维联系也被激活,这些被激活的神经元可能与运动病发生的复杂机制有关。     

Glutamatergic vestibular neurons express Fos after vestibular stimulation and project to the NTS and the PBN in rats

In this study, retrograde tracing method combined with phosphate-activated glutaminase (PAG) and Fos immunofluorescence histochemistry was used to identify glutamatergic vestibular nucleus (VN) neurons receiving vestibular inputs and projecting to the nucleus of the solitary tract (NTS) and the parabrachial nucleus (PBN). Conscious animals were subjected to 120 min Ferris-wheel like rotation stimulation. Neuronal activation was assessed by Fos expression in the nucleus of VN neurons. After Fluoro-gold (FG) injection into the caudal NTS, approximately 48% FG-labeled VN neurons were immunoreactive for PAG, and about 14% PAG/FG double-labeled neurons co-existed with Fos. Following FG injection into the PBN, approximately 56% FG-labeled VN neurons were double-labeled with PAG, and about 12% of the PAG/FG double-labeled neurons also expressed Fos. Careful examination of the typology and distribution pattern of these PAG-immunoreactive neurons indicated that the vast majority of these neurons were glutamatergic rather than GABAergic. These results suggest that PAG-immunoreactive VN neurons might constitute excitatory glutamatergic VN-NTS and VN-PBN transmission pathways and these pathways might be involved in vestibulo-autonomic reflexes during vestibular stimulation.     

Gene expression in rat vestibular and reticular structures during and after space flight

Space flight produces profound changes of neuronal activity in the mammalian vestibular and reticular systems, affecting postural and motor functions. These changes are compensated over time by plastic alterations in the brain. Immediate early genes (IEGs) are useful indicators of both activity changes and neuronal plasticity. We studied the expression of two IEG protein products [Fos and Fos-related antigens (FRAs)] with different cell persistence times (hours and days, respectively) to identify brainstem vestibular and reticular structures involved in adaptation to microgravity and readaptation to 1 G (gravity) during the NASA Neurolab Mission (STS-90). IEG protein expression in flight animals was compared to that of ground controls using Fisher 344 rats killed 1 and 12 days after launch and 1 and 14 days after landing. An increase in the number of Fos-protein-positive cells in vestibular (especially medial and spinal) regions was observed 1 day after launch and 1 day after landing. Fos-positive cell numbers were no different from controls 12 days after launch or 14 days after landing. No G-related changes in IEG expression were observed in the lateral vestibular nucleus. The pattern of FRA protein expression was generally similar to that of Fos, except at 1 day after landing, when FRA-expressing cells were observed throughout the whole spinal vestibular nucleus, but only in the caudal part of the medial vestibular nucleus. Fos expression was found throughout the entire medial vestibular nucleus at this time. While both Fos and FRA expression patterns may reflect the increased G force experienced during take-off and landing, the Fos pattern may additionally reflect recent rebound episodes of rapid eye movement (REM) sleep following forced wakefulness, especially after landing. Pontine activity sources producing rhythmic discharges of vestibulo-oculomotor neurons during REM sleep could substitute for labyrinthine signals after exposure to microgravity, contributing to activity-related plastic changes leading to G readaptation. Reticular structures exhibited a contrasting pattern of changes in the numbers of Fos- and FRA-positive cells suggestive of a major influence from proprioceptive inputs, and plastic re-weighting of inputs after landing. Asymmetric induction of Fos and FRAs observed in some vestibular nuclei 1 day after landing suggests that activity asymmetries between bilateral otolith organs, their primary labyrinthine afferents, and vestibular nuclei may become unmasked during flight.     

大鼠束缚后脑内Fos蛋白的表达

目的探讨大鼠束缚后对大鼠脑内Fos蛋白表达的影响。方法将大鼠束缚于小的塑料桶内1、3或6h,于解束后30min处死,脑组织进行Fos蛋白免疫组织化学染色。结果Fos阳性神经元表达于1．前脑：扣带回、新皮质(尤其是第3和5层)、外侧隔核、杏仁中央核;2．间脑：下丘脑视前区、下丘脑外侧区、视上核、室旁核、第三脑室室周区、弓状核、丘脑室旁核、外侧膝状体、内侧膝状体;3．脑干：中脑的上丘视性层、中脑导水管周围灰质、下丘的皮质部;脑桥的臂旁外侧核、蓝斑、A5区;延髓的耳蜗核、延髓内脏带(MVZ)等处。Fos表达的时问规律是束缚1h最高,3h次之,6h最少。结论大鼠被束缚后全脑多处核团的神经元发生不同程度的Fos反应,随着束缚时间的延长,动物产生适应性,Fos表达减少。     

后肢去负荷改变大鼠前庭复合体各亚核Fos表达(英文)

目的:以Fos蛋白表达为指标,分别研究后肢去负荷(hindlimb unloading,HU)以及去负荷一定时间后双轴旋转刺激对大鼠前庭核复合体(vestibular nucleus complex,VNC)各亚核神经元活动的影响。方法:动物分为后肢去负荷(即HU)组、HU处理后双轴旋转组(HU-R)和对照组(即假运动刺激组)。应用免疫组织化学ABC法,检查各组动物VNC各核团内Fos蛋白表达,统计Fos阳性神经元数目。结果:后肢去负荷1d可刺激VNC吻侧部前庭内侧核(MVe)、前庭下核(SpVe)两亚核内Fos阳性神经元数目较对照组有显著增加;但是,随后肢去负荷时间延长,VNC各核Fos阳性神经元数趋向于回到对照水平。2h双轴旋转刺激HU1d大鼠后,VNC所有核团内Fos阳性神经元数目都显著性增加;大鼠HU7d后再行双轴旋转刺激,MVe和SpVe内Fos阳性神经元数目有显著性增加。结论:地面模拟失重可刺激大鼠VNC神经元活动,随时间延长,模拟失重动物出现适应现象,前庭神经元活动减弱;运动刺激前庭感受器后,模拟失重动物VNC神经元活动显著增强。     

缺氧诱导大鼠中缝背核远位触液神经元表达Fos蛋白(英文)

本文旨在研究缺氧刺激条件下中缝背核内远位触液神经元Fos蛋白的表达情况。应用低压氧舱仿海拔8000米高空缺氧模型,采用侧脑室注射CB(霍乱毒素B亚单位)标记中缝背核内的远位触液神经元,并用Fos免疫组化和CB/Fos免疫组化双重染色方法显示Fos在中缝背核远位触液神经元内的表达情况。结果表明中缝背核内存在大量的CB标记神经元(31.16±3.36/每张切片)。缺氧实验组中缝背核内Fos阳性神经元数显著增加(40.28±2.17/每张切片,P<0.05),并可见CB/Fos双标神经元(2.00±0.39/每张切片)。对照组中缝背核内Fos阳性神经元数较少(5.55±0.81/每张切片),未见CB/Fos双标神经元。本文结果提示在缺氧刺激条件下,中缝背核内部分远位触液神经元在脑脑脊液之间的信息传递及功能调节中可能发挥一定作用。     

Female responses to acute and repeated restraint stress differ from those in males

Chronic stress is implicated in diseases which differentially affect men and women. This study investigated how the activation of neuronal subpopulations contributes to changes in neuroendocrine regulation that predispose members of each sex to stress-related health challenges. Adult male and female rats were restrained in single (acute) or 14 consecutive daily (repeated) 30 min sessions; brain sections were immunohistochemically stained for Fos, arginine vasopressin (AVP) or glucocorticoid receptor (GR) within the paraventricular hypothalamic nucleus (PVH). Acute restraint increased the number of PVH cells expressing Fos, with greater increases in males than females. Habituated responses were seen following repeated stress in both sexes, with no sex differences between groups. No sex differences were found in the number of neurons co-expressing Fos and AVP. Absolute counts of cellular Fos and GR co-localization mirrored Fos expression. In contrast, when doubly-labeled cells were normalized to staining for Fos alone, females showed greater numbers of Fos- and GR-positive cells than males after both acute and repeated stress. These data demonstrate that sex-specific stress responses are evident at the level of neuronal activation, and may contribute to different consequences of chronic stress in females versus males. Females may be more sensitive to glucocorticoid negative feedback, suggesting that sex-dependent differences in the efficiency of initiating and terminating stress responses may exist. Understanding the neural and endocrine pathways that mediate these functions in males and females will inform targeted therapeutic strategies to alleviate stress and the sex-specific afflictions with which it is associated.     

胃肠道伤害性刺激诱导大鼠孤束核,视上核,室旁核内FOS蛋白的表达

用抗ＦＯＳ免疫组化技术，观察胃肠道伤害性刺激诱导大鼠孤束核、视上核、室旁核内ｃ－ｆｏｓ的表达，并结合抗ＴＨ免疫双重染色技术，探讨孤束核内儿茶酚胺能神经元与ＦＯＳ蛋白的关系，结果表明：ＦＯＳ阳性细胞主要分布于孤束核的连合亚核、内业核以及背侧周边区，说明孤束核是内脏伤害性信息初级传和冲动的直接反应区。在下丘脑内主要２于视上核和室旁核，提示视上核和室旁核在内脏伤害性刺激的传递中起中毒作用。在双标切片中，     

Somatic noxious mechanical stimulation induces Fos expression in the postsynaptic dorsal column neurons in laminae III and IV of the rat spinal dorsal horn

This study was conducted to ascertain the possible expression of Fos-like immunoreactivity (Fos-LI) in the postsynaptic dorsal column (PSDC) neurons in response to noxious mechanical stimulation of the forepaw glabrous area of normal rats. For this purpose, Fos immunohistochemistry along with Fluoro-Gold (FG) retrograde tracing was utilized. After repeated noxious pinching of the forepaw glabrous area, there was a marked increase in number of Fos-LI neurons in the dorsal horn, including Rexed's laminae III and IV, at C5-T1 spinal cord segments ipsilateral to the stimulation. Between segments C5 and T1, about 40% of the Fos-LI neurons in laminae III and IV were distributed at segment C7. In the rats subjected to the noxious pinch coupled with FG injection into the right cuneate nucleus, PSDC neurons double labeled with Fos and FG were localized in the ipsilateral laminae III and IV extending from segment C5 to T1, with about 70% of them distributed at segments C6 and C7. At segment C6 or C7, double-labeled neurons made up about 10% of the PSDC neurons that projected their axons to the cuneate nucleus. Most of the double-labeled neurons appeared fusiform with their primary dendrites projected dorso-ventrally. The present results suggest that the morphologically distinct, subclasses of PSDC neurons in spinal laminae III and IV may contribute to the central transmission of mechanical nociceptive information through the dorsal column into the cuneate nucleus.     

Effect of daily linear acceleration training on the hypergravity-induced vomiting response in house musk shrew (Suncus murinus)

The effects of repeated linear acceleration training and the antimotion sickness drug, promethazine, on hypergravity-induced motion sickness were examined in musk shrew (Suncus murinus), which is known to show a vomiting response to motion stimulation. Animals were assigned into five groups: vestibular intact, untreated animals (Sham), vestibular lesioned (VL) animals, vestibular intact animals with promethazine hydrochloride administered as daily drinking water (Prom), vestibular intact animals who underwent horizontal linear accelerator motion training (Train), and vestibular intact animals treated with both promethazine hydrochloride and linear acceleration training (Prom + Train). In Sham animals, the number of vomiting episodes was 14 ± 2 during 2 G exposure for 10 min, and was accompanied by intense Fos expression in the medial vestibular nucleus (MVe), the nucleus of the solitary tract (NTS), the area postrema (AP), and the paraventricular hypothalamic nucleus (PVN). The vomiting response and Fos expression were completely abolished in VL animals, indicating that these responses are mediated via the vestibular system. Although Train and Prom animals experienced a significantly reduced number of hypergravity-induced vomiting episodes compared with Sham animals, the effect was significantly greater in Train animals than in Prom animals. Fos expression in the NTS, AP, and PVN were significantly more reduced in Train animals than in Prom animals. Higher dose of bolus injection of promethazine (50 mg/kg, i.p.) completely abolished the vomiting episodes, although the animals were drowsy and sedated due to side effects. In conclusion, daily linear acceleration training and promethazine could prevent the hypergravity-induced vomiting episodes.     

双轴旋转运动刺激后大鼠中缝大核神经元活动分析

目的:分析大鼠经引发晕动病的双轴旋转运动刺激后,中缝背核(DR)内5-HT能神经元激活状况,以探讨5-HT水平与前庭刺激的关系.方法:将雄性SD大鼠随机分成两组:对照组和双轴旋转运动刺激组.所有动物装入定做的有机玻璃圆筒内,并于黑暗中进行如下处理2h:运动刺激组动物以电动马达驱动的双轴旋转运动刺激;对照组动物放置在距刺激仪器20 cm的位置.应用包含DR的冠状脑切片,以双重免疫荧光标记技术标记5-HT和Fos蛋白,并对标记神经元进行计数和统计分析.结果:对照组和旋转运动刺激组的Fos阳性神经元、5-HT阳性神经元以及Fos/5-HT双标记神经元的数目分别是:93.4 ±12.0 vs 153.1 ±21.1、528.5±36.0vs 531.1±23.4和15.1 ±11.3 vs 30.8 ±11.3.t检验分析显示两组Fos阳性神经元数目有显著性差异(P＜0.05);Fos/5-HT双标神经元数目在旋转运动刺激后有增加趋势.结论:引发晕动病的双轴旋转运动能激活中缝背核内的神经元,其中的5-HT能神经元也对刺激有反应.     

内脏伤害性刺激诱导的大鼠延髓内Fos表达

用抗Ｆｏｓ蛋白和酷氨酸羟化酶（ＴＨ）的免疫组织化学方法，对大鼠两种内脏伤害性刺激诱导的大鼠延髓Ｆｏｓ表达情况及其与儿茶酚胺能神经元的关系进行了观察。提示延髓内脏带半数以上的儿茶酚胺神经元参与对内脏伤害性刺激的反应。     

Bright light produces Fos-positive neurons in caudal trigeminal brainstem

Excessive discomfort after exposure to bright light often occurs after ocular injury and during headache. Although the trigeminal nerve is necessary for light-evoked discomfort, the mechanisms underlying this phenomenon, often referred to generally as photophobia, are not well defined. Quantitative Fos-like immunoreactivity (Fos-LI) was used to determine the pattern of neuronal activation in the caudal brainstem after bright light stimulation and, secondly, whether a neurovascular mechanism within the eye contributes to this response. Under barbiturate anesthesia, male rats were exposed to low (1×10⁴ lx) or high intensity (2×10⁴ lx) light delivered from a thermal neutral source for 30 min (30 s ON, 30 s OFF) and allowed to survive for 90 min. Intensity-dependent increases in Fos-LI were seen in laminae I–II at the trigeminal caudalis/cervical cord junction region (Vc/C1) and nucleus tractus solitarius (NTS). Fos-LI also increased at the trigeminal interpolaris/caudalis transition (Vi/Vc_vl) and dorsal paratrigeminal (dPa5) regions independent of intensity. Intravitreal injection of norepinephrine greatly reduced light-evoked Fos-LI at the Vc/C1, dPa5 and NTS, but not at the Vi/Vc transition. Lidocaine applied to the ocular surface had no effect on Fos-LI produced in trigeminal brainstem regions. These results suggested that multiple regions of the caudal trigeminal brainstem complex integrate light-related sensory information. Fos-LI produced at the dPa5 and NTS, coupled with norepinephrine-induced inhibition, was consistent with the hypothesis that light-evoked activation of trigeminal brainstem neurons involves an intraocular neurovascular mechanism with little contribution from neurons that supply the ocular surface.     

Intravenous administration of interleukin-1β induces Fos-like immunoreactivity in corticotropin-releasing hormone neurons in the paraventricular hypothalamic nucleus of the rat

It has been shown that acute administration of recombinant human interleukin 1β (IL-1) to rats elicits an activation of the pituitary-adrenal axis. In the present study we investigated immunohistochemically the expression of Fos-like immunoreactivity (Fos-LI) in the hypothalamus of rats following intravenous injection of IL-1. One, 2 and 4 h after IL-1 or physiological saline injections, rats were killed and perfused, and the brains processed for Fos-immunohistochemistry. Dense populations of neurons containing Fos-LI-positive nuclei were found in the paraventricular hypothalamic nuclei (PVH) of IL-1-treated rats. In particular, the dorsal medial parvocellular part, but also some of the other parvocellular subdivisions contained many Fos-LI neurons. Maximal induction of staining was found at a dose of 5 μ/rat after 1 or 2 h survival, while immunostaining had decreased to almost control levels after 4h. No Fos-LI was found in the PVH of control aminals. Double immunocytochemical staining for Fos and corticotropin-releasing hormone (CRH) revealed that Fos-LI was predominantly present in parvocellular CRH-containing neurons of the PVH. The finding that peripherally injected IL-1 induces Fos-LI in hypothalamic CRH neurons strengthens the hypothesis that these neurons are part of the circuitry mediating IL-1-induced activation of the pituitary-adrenal axis.     

在戊四氮致痫大鼠早期前脑中0X-42和Fos蛋白的表达变化

研究大鼠在戊四氮导致癫痫发作早期前脑内小胶质细胞的变化及其与神经元的关系，本研究应用免疫组织化学法分别显示前脑内OX-42和Fos蛋白表达的时程变化，并用双重标记显示OX-42和Fos阳性细胞的相互关系。结果发现：在戊四氮导致大鼠癫痫发作早期（从15min到360min），前脑的小胶质细胞0X42表达阳性，随着存活时间的变化，OX42的阳性反应经历逐渐升高又降低的过程；Fos蛋白在神经元和小胶质细胞中有表达，也呈现逐渐升高又降低的变化；Fos在小胶质细胞表达高峰的时间早于在神经元的表达；另外0X-42阳性小胶质细胞和Fos阳性神经元在前脑分布基本相同，主要分布在大脑皮层．海马．杏仁核等部位。以上结果表明，前脑的小胶质细胞和神经元一样在戊四氮所致癫痫发作的早期表现明显的反应，但小胶质细胞反应的意义有待进一步研究。     

在戊四氮致痫大鼠早期前脑中OX-42和Fos蛋白的表达变化

研究大鼠在戊四氮导致癫痫发作早期前脑内小胶质细胞的变化及其与神经元的关系,本研究应用免疫组织化学法分别显示前脑内OX-42和Fos蛋白表达的时程变化,并用双重标记显示OX-42和Fos阳性细胞的相互关系。结果发现:在戊四氮导致大鼠癫痫发作早期(从15min到360min),前脑的小胶质细胞OX-42表达阳性,随着存活时间的变化,OX-42的阳性反应经历逐渐升高又降低的过程;Fos蛋白在神经元和小胶质细胞中有表达,也呈现逐渐升高又降低的变化;Fos在小胶质细胞表达高峰的时间早于在神经元的表达;另外OX-42阳性小胶质细胞和Fos阳性神经元在前脑分布基本相同,主要分布在大脑皮层、海马、杏仁核等部位。以上结果表明,前脑的小胶质细胞和神经元一样在戊四氮所致癫痫发作的早期表现明显的反应,但小胶质细胞反应的意义有待进一步研究。     

热应激对大鼠脑桥臂旁核Fos和GFAP表达的影响

为了探讨急性热应激(heat stress,HS)后大鼠脑桥臂旁核Fos蛋白及胶质原纤维酸性蛋白(glial fibrillary acidic protein,GFAP)的表达变化,本实验将大鼠置于恒温恒湿温度舱内,舱内温度调至24℃、34℃、38.5℃或42℃、湿度为60%,建立HS大鼠模型,1h后结束刺激,立即断头取脑,应用免疫组织化学染色方法检测脑桥臂旁核内Fos蛋白和GFAP的表达情况。结果显示:脑桥臂旁核内可见大量的Fos样免疫阳性神经元和GFAP样免疫阳性的星形胶质细胞,其中在24℃~38.5℃组Fos蛋白的表达随温度增加而增加,38.5℃组为高峰,而在42℃组Fos蛋白表达又有所减少。GFAP样免疫阳性星形胶质细胞在34℃组出现胞体变大,突起增粗的现象,且细胞数量增加,38.5℃组最显著,但在42℃组星形胶质细胞的数量则有所减少,并出现胞体形态不规则、突起断裂的现象。本实验结果表明脑桥臂旁核参与热应激反应的神经免疫调节,可能为此调节通路的中继站之一。     

Functional organization of vestibulofastigial projection in the horizontal semicircular canal system in the cat

Spike potentials of fastigial nucleus neurons were recorded extracellularly in decerebrate, unanesthetized cats. The neurons responding to head rotation in the horizontal plane with a type I fashion were located mainly in the middle and caudal regions of the fastigial nucleus. Three fourth of these fastigial type I neurons were antidromically activated by stimulation of the contralateral vestibular nuclei. These neurons were excited transsynaptically from the ipsilateral vestibular nerve or nuclei. Intra cellular recordings were made from those neurons which were located in the caudal half of the fastigial nucleus and were activated antidromically from the contralateral vestibular nuclei. Stimulation of the ipsilateral vestibular nerve produced EPSPs in these neurons with latencies of 1.0-6.6 msec. The shortest conduction time along primary vestibular aggerents from the labyrinth to the ipsilateral fastigial nucleus was 0,7 msec. The EPSPs with the shortest latency of 1.0 msec were therefore postulated to be due to monosynaptic connections of primary vestibular afferents with fastigial neurons. Stimulation of ipsilateral vestibular nuclei also produced monosynaptic EPSPs in fastigial neurons. These EPSPs were facilitated by conditioning stimulation of the ipsilateral vestibular nerve, indicating the existence of polysynaptic activation of fastigial neurons from the ipsilateral vestibular nerve through the vestibular nuclei.     

Contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus produced by acute injury to the masseter muscle during persistent temporomandibular joint inflammation in rats

We investigated the contribution of peripheral 5-HT2A or 5-HT3 receptors to Fos expression in the trigeminal spinal nucleus (VSP) following acute masseter muscle injury in male rats with or without temporomandibular joint (TMJ) inflammation persisting for 7 days. TMJ inflammation was evoked by an injection of complete Freund’s adjuvant (CFA). Two hours after formalin injection into the masseter muscle produced Fos-like immunoreactivity (Fos-LI) in several regions of the VSP and upper cervical spinal cord (C2), such as ventrolateral (vl) area of the trigeminal subnucleus caudalis (Vc)/subnucleus interpolaris (Vi) transition (vl-Vi/Vc), paratrigeminal nucleus (dPa5), middle portion of the Vc (mid-Vc) and Vc/C2 transition (Vc/C2) regions in both groups. Significant increases in the number of Fos-LI were observed in these areas in CFA group compared with non-CFA group. TMJ inflammation alone did not induce a significant level of Fos-LI in the VSP. In order to assess the effect of antagonizing 5-HT2A or 5-HT3 receptors on formalin-induced Fos-LI, rats were pre-treated with local (masseter muscle) administration of ketanserin or tropisetron (0.01, 0.1 mg/rat) 20 min prior to formalin injection. In CFA group, these antagonists given locally reduced the Fos-LI response in the laminae I–II at the mid-Vc and Vc/C2 regions. These antagonists reduced the Fos-LI response in the dPa5, but not in the vl-Vi/Vc region. The Fos-LI response was not affected by i.v. administration of ketanserin (0.01, 0.1 mg/rat) or tropisetron (0.01 mg/rat). In non-CFA group, these antagonists given locally did not reduce the Fos-LI response. These results suggest that peripheral 5-HT2A and 5-HT3 receptors contribute to nociceptive processing in the masseter muscle in TMJ inflammatory conditions.