腹外侧眶皮层中miR-200对慢性应激所致大鼠抑郁行为调控作用研究

目的:观察慢性不可预知温和应激(CUMS)模型大鼠腹外侧眶皮层(VLO)内miR-200和双特异性磷酸酶1(DUSP1)表达变化,并探讨VLO内注射miR-200模拟物对抑郁行为的调控作用及机制。方法:大鼠建立CUMS抑郁模型后分为5组:CUMS+miR-200模拟物组(VLO内注射20 pmol miR-200 mimic);CUMS+阴性对照组(VLO内注射20 pmol阴性对照siRNA);无应激+阴性对照组;无应激+miR-200模拟物组;CUMS+氟西汀(10 mg/kg/d)组。依次进行蔗糖偏爱测试、旷场实验、高架十字迷宫实验。Western Blot检测VLO内DUSP1、细胞外调节蛋白激酶(ERK)、pERK蛋白表达。结果:与无应激组比较,CUMS组大鼠体重降低(P0.0001)、蔗糖偏爱下降(P=0.008),VLO中miR-200表达减少(P0.0001),DUSP1表达增高(P=0.0054);与CUMS+阴性对照组比较,CUMS+miR-200模拟物组大鼠蔗糖偏爱率(P=0.028),开放臂进入时间(P=0.031)和进入次数(P0.0001)均升高,总活动距离不受影响;与CUMS+阴性对照组比较,CUMS+miR-200模拟物组VLO中DUSP1(P=0.046)和pERK(P=0.042)蛋白水平显著升高。结论:慢性应激性环境所致抑郁样行为与VLO内pERK下调有关,miR-200可直接下调VLO内DUSP1表达,提高pERK表达并最终改善抑郁症状。     

Regional inactivations of primate ventral prefrontal cortex reveal two distinct mechanisms underlying negative bias in decision making

Dysregulation of the orbitofrontal and ventrolateral prefrontal cortices is implicated in anxiety and mood disorders, but the specific contributions of each region are unknown, including how they gate the impact of threat on decision making. To address this, the effects of GABAergic inactivation of these regions were studied in marmoset monkeys performing an instrumental approach–avoidance decision-making task that is sensitive to changes in anxiety. Inactivation of either region induced a negative bias away from punishment that could be ameliorated with anxiolytic treatment. However, whereas the effects of ventrolateral prefrontal cortex inactivation on punishment avoidance were seen immediately, those of orbitofrontal cortex inactivation were delayed and their expression was dependent upon an amygdala–anterior hippocampal circuit. We propose that these negative biases result from deficits in attentional control and punishment prediction, respectively, and that they provide the basis for understanding how distinct regional prefrontal dysregulation contributes to the heterogeneity of anxiety disorders with implications for cognitive-behavioral treatment strategies.Sensitivity to threat, and the appropriate interpretation of potential threat, is crucial for an organism to survive and make optimal decisions with respect to its environment. Overestimation of threat and hypersensitivity to negative emotional information are known to inappropriately impact cost–benefit decision making in patients suffering from anxiety and depression (1, 2). This hypersensitivity is thought to be due to dysregulation within the prefrontal cortex (PFC), but how the PFC contributes to aversive processing and how it gates the impact of negative emotional information on decision making are still poorly understood.There are a number of distinct brain regions within the PFC that are dysregulated in anxiety and mood disorders, including the orbitofrontal (OFC), ventrolateral prefrontal (vlPFC), and medial prefrontal (mPFC) cortices (3–5). Of these, a region within mPFC (pregenual cingulate cortex) has been implicated in regulating negative emotional valence in decision making (6), but the contribution of the other regions remains unknown. Given the lifetime prevalence and economic cost of anxiety and depression (7), understanding how these distinct prefrontal subregions modulate the impact of emotion on decision making is crucial to identify how different types of prefrontal dysregulation contribute to the heterogeneity of anxiety and mood disorders and thus guide the development of personalized treatments. Despite the uncertainty regarding the rodent correlates of these other prefrontal regions, in particular vlPFC, there have been few studies investigating the selective contribution of these other prefrontal regions to negative decision making in primates, as most primate studies focus on reward-guided decision making (8, 9; but see refs. 10–13). However, we showed previously that selective excitotoxic lesions of either anterior OFC (antOFC; area 11) or vlPFC (area 12) heighten anxiety and Pavlovian fear responses in marmoset monkeys, demonstrating that both regions contribute independently to the regulation of negative emotion (14), but their differential contribution and their involvement in modulating the impact of anxiety on decision making remains unknown. To address this, we developed an approach–avoidance conflict task suitable for marmoset monkeys and used anatomically specific intracerebral infusions and anxiolytic drug treatment to determine how temporary inactivation of these regions affected cost–benefit decision making.     

Effects of Pergolide,A Dopamine Receptor Agonist,and Clondine on Cardiovascular Responses Evoked by Activation of Peripheral Sympathetic Outflow in Rats

In pentobarbital anesthetized rats, pergolide (10.0 μ/kg, i.v.) and clonidine (3.0 μ/kg, i.v.) produced similar significant decreases in heart rate and carotid artery pressure. Sulpiride (0.3 mg/kg, i.v.) did not change the effects of clonidine but inhibited entirely the hypotension and partly the bradycardia produced by pergolide. However, yohimbine (0.3 mg/kg) antagonized the cardiovascular effects of clonidine and reduced the bradycardia produced by pergolide. In pithed rats with an experimental, submaximal tachycardia evoked by sustained electrical stimulation of the thoracic sympathetic outflow pergolide and clonidine decreased heart rate. This effect was antagonized by yohimbine (0.1 mg/kg, i.v.) but by not sulpiride (0.3 mg/kg, i.v.). In adrenalectomized, propranolol pretreated pithed rats the pressor responses to 15 sec periods of electrical stimulation of the entire spinal cord were depressed only by pergolide. This effect was blocked by sulpiride. These findings indicate that in the pithed rat the inhibition of neural sympathetic tachycardia by clonidine and pergolide is mediated by stimulation of cardiac presynaptic α₂-adrenoceptors. However, only pergolide decreased significantly the pressor responses evoked by electrical stimulation of the peripheral sympathetic outflow and this effect resulted from activation of dopamine receptors located on postganglionic sympathetic neurons innervating resistance blood vessels. Thus, vascular presynaptic α₂-adrenceptors do not appear to contribute to the significant hypotensive effect exerted by 3.0 μ/kg, i.v.     

8-OH-DPAT-induced hypotensive action and sympathoexcitatory neurons in the rostral ventrolateral medulla of the rat

We examined whether the selective 5-hydroxytryptamine 1A (5-HT_1A) receptor agonist 8-hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT) injected systemically can act directly on sympathoexcitatory neurons located in the rostral ventrolateral medulla (RVLM) to cause the hypotensive effect of this agent in rats. Microinjections of 8-OH-DPAT and buspirone into the RVLM produced a dose-dependent decrease in blood pressure. Microinjections of spiperone and pindolol, 5-HT_1A antagonists, into the RVLM inhibited the depressor response to 8-OH-DPAT intravenously injected or injected into the RVLM. Microiontophoretic application of 8-OH-DPAT onto RVLM sympathoexcitatory neurons inhibited the firing of RVLM sympathoexcitatory neurons and the inhibition of unit activity by 8-OH-DPAT was blocked by rrmicroiontophoretic spiperone. Intravenous administration of 8-OH-DPAT also inhibited the firing of these neurons. Microiontophoretic application of spiperone onto the RVLM sympathoexcitatory neurons reversed the inhibitory response to intravenous 8-OH-DPAT. These results are consistent with the hypothesis that 8-OH-DPAT may exert a portion of its hypotensive effect through a direct inhibition of RVLM sympathoexcitatory neurons in rats. The receptor involved is probably the 5-HT_1A type.     

Neurons in the hypothalamic paraventricular nucleus that project to the rostral ventrolateral medulla are activated by haemorrhage

The retrogradely-transported tracer, rhodamine-tagged microspheres, was injected into the pressor region of the rostral ventrolateral medulla (RVLM) to identify paraventricular neurons in the hypothalamus that project to the RVLM. The protein, Fos, was detected immunohistochemically and used to highlight neurons that were activated by a hypotensive haemorrhage. Compared to controls, Fos production was increased by approximately 3-fold in the paraventricular nucleus (P<0.009) and there was a significant increase in the number of retrogradely-labelled cells that expressed Fos. These represented 5% of the retrogradely-labelled cell population. The results suggest that a small subpopulation of PVN neurons projecting to the RVLM are activated by haemorrhage and may be involved in the reflex responses initiated by that stimulus.     

Ethanol inhibits chemoreflex excitation of reticulospinal vasomotor neurons

In anesthetized and ventilated rats, activation of carotid chemoreceptors with intracarotid administration of 100 nmol sodium cyanide rapidly excited the spinal cord-projecting vasomotor neurons in the rostroventrolateral reticular nucleus (RVL) of the medulla oblongata and sympathetic nerves and increased arterial pressure. The chemoreflex symphthoexcitatory pressor responses were attenuated by an acute systemac administration of ethanol at 0.45 g/kg, but not at 45 mg/kg. The ethanol effects were observed at the level of RVL-spinal vasomotor neurons, in attenuating the neuronal responses to the chemoreflex excitation and direct iontophoresis of N-methyl- -aspartic acid (NMDA) but without altering responses of the carotid sinus nerves to intracarotid cyanide. The effect of ethanol on the RVL neurons was further defined as blocking NMDA-evoked inward current in the corresponding spontaneously active RVL neurons in vitro. The results indicate that acute ethanol intoxication markedly influences NMDA receptor activation and arterial chemoreflexes. The relevance of the type of action to clinical hypertension in chronic and heavy drinkers is discussed.     

Localization and characterization of angiotensin II receptor binding and angiotensin converting enzyme in the human medulla oblongata

Angiotensin II receptor and angiotensin converting enzyme distributions in the human medulla oblongata were localised by quantitative in vitro autoradiography. Angiotensin II receptors were labelled with the antagonist analogue 125I-[Sar1, Ile8] AII while angiotensin converting enzyme was labelled with 125I-351A, a derivative of the specific converting enzyme inhibitor, lisinopril. Angiotensin II receptor binding and angiotensin converting enzyme are present in high concentrations in the nucleus of the solitary tract, the dorsal motor nucleus of vagus, the rostral and caudal ventrolateral reticular nucleus, and in a band connecting the dorsal and ventral regions. In the rostral and caudal ventrolateral reticular nucleus, angiotensin II receptors are distributed in a punctate pattern that registers with neuronal cell bodies. The distribution and density of these cell bodies closely resemble those of catecholamine-containing neurones mapped by others. In view of the known interactions of angiotensin II with both central and peripheral catecholamine-containing neurons of laboratory animals, the current anatomical findings suggest similar interactions between these neuroactive compounds in the human central nervous system. The presence of angiotensin II receptors and angiotensin converting enzyme in the nucleus of the solitary tract, dorsal motor nucleus of vagus, and rostral and caudal ventrolateral reticular nucleus demonstrates sites for central angiotensin II to exert its known actions on vasopressin release and autonomic functions including blood pressure control. These data also suggest a possible interaction between angiotensin II and central catecholeminergic systems.     

Anatomical evidence that hypertension associated with the defence reaction in the cat is mediated by a direct projection from a restricted portion of the midbrain periaqueductal grey to the subretrofacial nucleus of the medulla

Wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injections were made at sites within a restricted portion of the midbrain periaqueductal grey region (PAG) of the cat at which microinjection of the excitant amino acid, d,l-homocysteic acid, elicits the strongest form of a defence reaction, including a hypertensive response. Among the revealed projections, significant anterograde labelling was found in a discrete region of the rostral ventrolateral medulla, the subretrofacial nucleus (SRF). In the cat, the SRF contains pressor neurones which project to the spinal preganglionic sympathetic outflow. The labelling was most marked ipsilaterally, although substantial contralateral labelling was also observed. To verify that the projection to the SRF originated from the restricted ‘defence region’ of the PAG, WGA-HRP or rhodamine-labelled microspheres were injected into physiologically-identified sites in the SRF. In all experiments, labelled neurones were found in the same restricted region of the PAG at which DLH injection evokes hypertension and behavioural signs of the defence reaction. The results are consistent with the hypothesis that a discrete cell group within the PAG mediates both somatic and autonomic components of the defence reaction and that the characteristic hypertensive response is mediated by a direct pathway from these PAG cells to pressor neurones in the SRF.     

Lateral hypothalamic and peripheral cardiovascular afferent inputs to ventrolateral medullary neurons

Experiments were done in chloralose anesthetized, paralyzed and artificially ventilated cats to identify single units in ventrolateral medulla (VLM) projecting directly to the intermediate gray (IG) region of the upper thoracic cord and responding to inputs from pressor sites in the anterior lateral hypothalamus (Hla) and carotid sinus (CSN) and aortic depressor (ADN) nerves. Forty-eight units were antidromically activated in VLM to stimulation of the IG at the level of T2. Of these 48 units, 15 (31%) were orthodromically excited by stimulation of the Hla with a mean latency of 15.8 +/- 2.1 ms. In addition, 8 of the 15 units responding to Hla stimulation were also excited orthodromically by stimulation of either the CSN or ADN or both. Of the remaining 33 units, 15 responded to stimulation of only the buffer nerves and 18 were unresponsive to the tested inputs. These results provide electrophysiological evidence for the existence of neurons in VLM which receive hypothalamic and buffer nerve inputs and suggest that the VLM plays a role in integrating and relaying cardiovascular afferent information from peripheral baroreceptors and chemoreceptors and from supramedullary centers to provide effector signals to spinal autonomic neurons involved in the control of the circulation.     

Convergent influence of the central nucleus of the amygdala and the paraventricular hypothalamic nucleus upon brainstem autonomic neurons as revealed by c-fos expression and anatomical tracing

Combinations of anatomical tracing with detection of Fos (the protein product of the immediate early gene c-fos) consequent to the stimulation of the central nucleus of the amygdala were used to explore the possibility that the hypothalamic paraventricular nucleus participates in the activation of brainstem neurons in the nucleus of the solitary tract and ventrolateral medulla. After injections of the anterograde tracer Phaseolus vulgaris leucoagglutinin in the paraventricular nucleus, labeled fibers and varicosities were found to impinge on catecholaminergic and non-catecholaminergic Fos-positive neurons in the brainstem. After injections of a retrograde tracer in the nucleus of the solitary tract or ventrolateral medulla, we observed that some of the Fos-positive neurons within the parvocellular paraventricular nucleus that project to the brainstem were catecholaminergic or oxytocinergic. The results indicate that direct and indirect inputs from the amygdala may influence the activity of autonomic neurons in the brainstem. The paraventricular nucleus, via its direct projections onto catecholaminergic and non-catecholaminergic neurons, may participate in activation of brainstem neurons. Activated catecholaminergic and oxytocinergic parvocellular neurons in the paraventricular nucleus may be involved in the transmission of autonomic signals from the amygdala toward the brainstem. ©1995 Wiley-Liss, Inc.