TNF-alpha-induced c-Fos generation in the nucleus of the solitary tract is blocked by NBQX and MK-801

Previous studies have shown that identified neurons of the nucleus of the solitary tract (NST) are excited by the cytokine tumor necrosis factor-alpha (TNF-alpha). Vagal afferent connections with the NST are predominantly glutaminergic. Therefore, we hypothesized that TNF-alpha effects on NST neurons may be via modulation of glutamate neurotransmission. The present study used activation of the immediate early gene product c-Fos as a marker for neuronal activation in the NST. c-Fos expression was evaluated after microinjections of TNF-alpha in the presence or absence of either the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium (NBQX) or the N-methyl-D- aspartate (NMDA) antagonist MK-801. To assess the specificity of the interaction between TNF-alpha and glutamate, c-Fos expression was also evaluated after injection of oxytocin (OT) (which has a direct excitatory effect in this area of the brain stem) in the presence and absence of NBQX or MK-801. c-Fos labeling was significantly increased in the NST after TNF-alpha exposure. Coinjection of either NBQX or MK-801 with TNF-alpha prevented significant c-Fos induction in the NST. Microinjections of OT also induced significant NST c-Fos elevation, but this expression was unaffected by coinjection of either antagonist with OT. These data lead us to conclude that TNF-alpha activation of NST neurons depends on glutamate and such an interaction is not generalized to all agonists that act on the NST.     

Responses of neurons of the solitary tract nucleus to noxious colorectal distension in rats

In experiments on anaesthetized rats, the neuronal mechanisms underlying processing of the nociceptive information from the colon within the nucleus of the solitary tract were studied. In addition, the role of nitric oxide in these processes was estimated. Analysis of changes in c-fos expression revealed that nociceptive colorectal distension (CRD) resulted in activation of neurons mainly in the medial, commissural, parvicellular and dorsomedial subnuclei of the solitary tract nucleus. Non-noxious CRD evoked in these subdivisions weak phasic excitatory neuronal responses. Under noxious CRD, neurons with phasic (58%) and tonic (42%) responses were revealed. The phasic neuron responses were significantly enhanced in comparison with non-noxious CRD. Inhibition of the neuronal NO-syntheses resulted in significant decrease of neuron responses to noxious CRD and the number of cells with tonic reactions. Therefore, neurons with tonic responses may be directly related to NO-depended processing ofnociceptive information from colon.     

Nucleus raphe obscurus participates in regulation of gallbladder motility through vagus and sympathetic nerves in rabbits

The aim of the present study is to investigate if the nucleus raphe obscurus (NRO) participate in regulating the gallbladder motility in rabbits. Rabbits were fasted for about 20-24 hours. After anesthetization with urethane, an incision was made at the middle of the abdomen and the gallbladder was exposed. A frog bladder connected with force transducer was inserted into the gallbladder through a small incision at the funds to record gallbladder motility (tonic contraction and phasic contraction). Glutamate and other chemicals were microinjected into NRO through a vitreous tube attached to a microsyringe. We found both the tonic contraction and phasic contraction of the gallbladder were enhanced after the glutamate was injected into NRO. GABA inhibited gallbladder motility if administrated in the same way. Microinjection of ketamine, NMDA (N-methyl-D-aspartate) receptor antagonist, into NRO inhibited the phasic contraction of gallbladder. Administration of CNQX (6-cyano-7-nitroquinoxaline-2, 3-dione), a non-NMDA receptor antagonist, enhanced the gallbladder tonic contraction. Pretreatment of ketamine into NRO attenuated the effect of glutamate, while pretreatment of CNQX had no effect on it. Intravenous injection of atropine or vagotomy completely abolished the effect of glutamate on gallbladder phasic contraction, while intravenous injection of phentolamine or transecting the spinal cord at T3-4 inhibited that on tonic contraction. Intravenous injection of propranolol did not influence the glutamate effect. These results suggested that glutamate in NRO participates in regulating the motility of the gallbladder through NMDA receptor. When excited, the NMDA receptors in NRO enhance the phasic contraction of the gallbladder through vagus nerve and peripheral M-receptors, and enhance the tonic contraction of the gallbladder through sympathetic nerve and peripheral alpha-receptors. GABA in NRO is also involved in the regulation of gallbladder motility.     

Postprandial neuronal activation in the nucleus of the solitary tract is partly mediated by CCK-A receptors

CCK-A receptors and neurons of the nucleus of the solitary tract (NTS) are involved in the regulation of food intake, and in rats, there is evidence for involvement of an intestinal vagal afferent pathway. Studies investigating the role of CCK-A receptors in activation of NTS neurons using highly selective CCK-A receptor agonists and antagonists have yielded conflicting data. In the present study, we investigated CCK-induced and postprandial activation of NTS neurons, together with food intake studies, in CCK-A receptor-deficient Otsuka Long-Evans Tokushima fatty (OLETF) rats. Activated NTS neurons were detected using immunohistological staining for c-Fos protein. Exogenous CCK increased the number of c-Fos protein-positive cells in the NTS of Sprague-Dawley and CCK-A receptor-intact Long-Evans Tokushima Otsuka (LETO) rats but had no effect in CCK-A receptor-deficient OLETF rats. Food intake-induced c-Fos protein expression in NTS neurons was significantly reduced in CCK-A receptor-deficient OLETF rats compared with Sprague-Dawley or LETO rats. Postprandial c-Fos protein expression in the NTS was also significantly decreased after pretreatment with the CCK-A receptor antagonist MK329 after both short- and long-term fasting periods. Exogenous CCK decreased cumulative food intake in Sprague-Dawley and LETO rats but not in OLETF rats. These data demonstrate that CCK-A receptors are involved in the CCK- and food-induced c-Fos protein expression in the NTS. Taken together with the results of the food intake studies, this suggests that activation of CCK-A receptors is involved in the postprandial activation of NTS neurons and in the regulation of food intake.     

Responses of caudate neurons to clicks in chronic experiments on cats

Spontaneous and evoked unit activity in response to repeated application of clicks at a frequency of 0.3–2.0 Hz in the caudate nucleus was studied by an extracellular recording technique in chronic experiments on cats. Four types of spontaneous unit activity in the caudate nucleus were distinguished. Altogether 44% of neurons tested responded by changes in spontaneous activity to clicks. Five types of responses of caudate neurons to clicks were discovered: phasic excitation, phasic inhibition, tonic activation, tonic inhibition, and mixed tonic responses; the commonest type was tonic activation. During prolonged stimulation by clicks extinction of the phasic responses was not observed. Complete or partial extinction of tonic responses in the course of frequent repetition of stimulation was observed in 33% of responding neurons. The question of possible convergence of specific and nonspecific influences on caudate neurons is discussed.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 12, No. 1, pp. 28–35, January–February, 1980.     

Central TRH receptor 1 antisense blocks cold-induced gastric emptying but not brain c-Fos induction

We studied whether TRH receptor 1 (TRH-R1) antisense oligodeoxynucleotides injected intracisternally, impaired acute cold-induced c-Fos expression in the brain and vagally mediated stimulation of gastric emptying in conscious rats. Cold exposure (4-6 degrees C, 90 min) increased gastric emptying and the number of c-Fos positive cells in the paraventricular nucleus of the hypothalamus, supraoptic nucleus, raphe pallidus, dorsal motor nucleus of the vagus, nucleus of the solitary tract and area postrema compared with rats at room temperature. TRH-R1 antisense abolished cold-induced stimulation of gastric transit but not c-Fos expression in the brain. TRH-R1 mismatch did not alter the gastric response to cold. These data indicate that central activation of TRH-R1 mediates cold-induced stimulation of gastric emptying but does not influence the induction of c-Fos expression in the brain.     

Interaction between unit responses of the cat cerebellar cortex during paired stimulation of the forelimbs

Interaction between spike responses of 41 cerebellar cortical neurons to electrical stimulation of the two forelimbs with different intervals between stimuli were studied in cats anesthetized with chloralose and pentobarbital. The responsiveness of neurons with a phasic type of discharge to testing stimulation of the limb was reduced for 300–500 msec or longer after conditioning stimulation of the other limb. Interaction between the responses was less clear in neurons with a tonic type of response. Interaction was absent or was summating in character if the stimuli were applied at the same times. Only if the intertrial intervals were 50–150 msec was regular inhibition of the responses of tonic type to the testing stimulus observed. It is postulated that the nucleus of the inferior olive participates in the interaction between phasic unit responses during simultaneous stimulation of the two limbs or to stimulation separated by short intervals (under 30 msec). With longer intervals between stimuli, interaction between responses of either type is connected with involvement of the lateral reticular nucleus. In the process of interaction competitive relations may develop between responses caused by impulses reaching neurons of the cerebellar cortex along climbing and mossy fibers.     

Brain pathways involved in the modulatory effects of noradrenaline in lateral septal area on cardiovascular responses

We have previously reported that stimulation of alpha-1 adrenoceptors by noradrenaline (NA) injected into the lateral septal area (LSA) of anaesthetized rats causes pressor and bradycardic responses that are mediated by acute vasopressin release into the circulation through activation of the paraventricular nucleus (PVN). Although the PVN is the final structure of this pathway, the LSA has no direct connections with the PVN, suggesting that other structures may connect these areas. To address this issue, the present study employed c-Fos immunohistochemistry to investigate changes caused by NA microinjection into the LSA in neuronal activation in brain structures related to systemic vasopressin release. NA microinjected in the LSA caused pressor and bradycardic responses, which were blocked by intraseptal administration of α-1 adrenoceptor antagonist (WB4101, 10?nmol/200?nL) or systemic V-1 receptor antagonist (dTyr(CH2)5(Me)AVP, 50?μg/kg). NA also increased c-Fos immunoreactivity in the prelimbic cortex (PL), infralimbic cortex (IL), dorsomedial periaqueductal gray (dmPAG), bed nucleus of the stria terminalis (BNST), PVN, and medial amygdala (MeA). No differences in the diagonal band of Broca, cingulate cortex, and dorsolateral periaqueductal gray (dlPAG) were found. Systemic administration of the vasopressin receptor antagonist dTyr AVP (CH2)5(Me) did not change the increase in c-Fos expression induced by intra-septal NA. This latter effect, however, was prevented by local injection of the alpha-1 adrenoceptor antagonist WB4101. These results suggest that areas such as the PL, IL, dmPAG, BNST, MeA, and PVN could be part of a circuit responsible for vasopressin release after activation of alpha-1 adrenoceptors in the LSA.     

The mechanism of interaction between the thalamic posterior lateral nucleus and the sensomotor cortex in rabbits

The thalamic posterior lateral nucleus was shown to exert phasic and tonic effects on the function of sensomotor cortex: the former in the form of pulvinar-cortical responses, and the latter in the form of foci of increased or decreased excitability. The findings suggest an inhibitory tonic effect of the sensomotor cortex on neuronal network of the posterior lateral nucleus.     

Responses of cat cerebellar cortical neurons to stimulation of the caudate nucleus,globus pallidus,and substantia nigra

Stimulation of the head of the caudate nucleus in cats anesthetized with chloralose and pentobarbital evoked spike responses of the Purkinje cells and other cerebellar cortical neurons in the paramedian lobes, lobulus simplex, and the tuber of the vermis. Phasic responses in the form of simple discharges (on account of activation of the neurons through mossy fibers) appeared mainly after a latent period of 5–12 and 14–20 msec; the latent period of responses consisting of complex discharges (on account of activation of Purkinje cells through climbing fibers) was 5–6, 9–22 msec, or more. Depending on the latent period, the spike responses differed in their rhythm of generation. In response to stimulation of the caudate nucleus with a frequency of 4–6/sec recruiting responses were found. An inhibitory pause was an invariable component of the tonic responses. During stimulation of the globus pallidus responses of the same types (phasic and tonic) appeared as during stimulation of the caudate nucleus, but they differed in the distribution of the neurons by latent period of spike responses. The minimal latent period was 4 msec. Recruiting also was observed during repetitive stimulation of the globus pallidus. During stimulation of the substantia nigra Pukinje cells activated by climbing fibers responded. Evoked complex discharges appeared after a stable latent period of 8.5±0.3 msec. Arguments are put forward regarding the role of the substantia nigra, the globus pallidus, nuclei of the inferior olive, and also the thalamic nuclei in the mechanism of caudato-cerebellar oligosynaptic and polysynaptic connections.N. I. Pirogov Medical Institute, Vinnitsa. Translated from Neirofiziologiya, Vol. 10, No. 4, pp. 375–384, July–August, 1978.     

Excitatory Amino Acid Receptors in the Ventral Tegmental Area Regulate Dopamine Release in the Ventral Striatum

Abstract: The role of excitatory amino acid (EAA) receptors located in the ventral tegmental area (VTA) in tonic and phasic regulation of dopamine release in the ventral striatum was investigated. Microdialysis in conscious rats was used to assess dopamine release primarily from the nucleus accumbens shell region of the ventral striatum while applying EAA antagonists or agonists to the VTA. Infusion of the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (25 and 100 µ M ) into the VTA did not affect dopamine release in the ventral striatum. In contrast, intra-VTA infusion of the NMDA receptor antagonist 2-amino-5-phosphopentanoic acid (100 and 500 µ M ) dose-dependently decreased the striatal release of dopamine. Intra-VTA application of the ionotropic EAA receptor agonists NMDA and AMPA dose-dependently (10 and 100 µ M ) increased dopamine efflux in the ventral striatum. However, infusion of 50 or 500 µ M trans -(±)-1-amino-1,3-cyclopentanedicarboxylic acid (ACPD), a metabotropic EAA receptor agonist, did not significantly affect these levels. These data suggest that NMDA receptors in the VTA exert a tonic excitatory influence on dopamine release in the ventral striatum. Furthermore, dopamine neurotransmission in this region may be enhanced by activation of NMDA and AMPA receptors, but not ACPD-sensitive metabotropic receptors, located in the VTA. These data further suggest that EAA regulation of dopamine release primarily occurs in the VTA as opposed to presynaptically at the terminal level.     

靶向毁损触液核对大鼠痛行为及脊髓背角5-HT和c-Fos表达的影响

目的：观察缺失触液核（CSF-contacting nucleus）对大鼠痛行为及脊髓背角痛相关物质5-羟色胺（5-HT）和c—Fas表达的影响,为触液核参与疼痛调制及机制提供实验依据。方法：成年雄性SD大鼠随机分为正常组（Control）,假手术组（Sham）,霍乱毒素亚单位B与辣根过氧化酶复合物（CB—HRP）组和毁损触液核组（Damage）。以机械缩足阈值（MWT）和热缩足潜伏期（耶儿）测定大鼠痛行为。免疫荧光法检测脊髓背角5-HT和c—Fos表达,并进行痛行为阈值与物质变化趋势的相关分析。结果：与Control、Sham和CB—HRP组相比,Damage组大鼠MWT和TWL明显降低（P〈0．05）。免疫荧光结果显示,正常大鼠触液核神经元高表达5-HT;Damage组大鼠触液核神经元数量随毁损天数延续逐渐减少,且在给予毁损剂CB—SAP第10天完全消失。与此同时脊髓背角5-HT和c—Fos表达量日趋增加,且与痛行为阈值变化趋势成负相关。结论：CB—SAP能科学可靠靶向毁损触液核,缺失触液核可致大鼠痛行为阈值减低,而脊髓背角5-HT和c—Fos表达量增加。本研究提示触液核参与了疼痛调制,且5-HT和c—Fos在此调制中发挥了重要作用。     

Processing of behaviorally relevant temporal parameters of acoustic stimuli by single neurons in the superior olivary nucleus of the leopard frog

Summary Response characteristics of 130 single neurons in the superior olivary nucleus of the northern leopard frog (Rana pipiens pipiens) were examined to determine their selectivity to various behaviorally relevant temporal parameters [rise-fall time, duration, and amplitude modulation (AM) rate of acoustic signals. Response functions were constructed with respect to each of these variables. Neurons with different temporal firing patterns such as tonic, phasic or phasic-burst firing patterns, participated in time domain analysis in specific manners. Phasic neurons manifested preferences for signals with short rise-fall times, thus possessing low-pass response functions with respect to this stimulus parameter; conversely, tonic and phasic-burst units were non-selective and possessed all-pass response functions. A distinction between temporal firing patterns was also observed for duration coding. Whereas phasic units showed no change in the mean spike count with a change in stimulus duration (i.e., all-pass duration response functions), tonic and phasic-burst units gave higher mean spike counts with an increase in stimulus duration (i.e., primary-like high-pass response functions). Phasic units manifested greater response selectivity for AM rate than did tonic or phasic-burst units, and many phasic units were tuned to a narrow range of modulation rates (i.e., band-pass). The results suggest that SON neurons play an important role in the processing of complex acoustic patterns; they perform extensive computations on AM rate as well as other temporal parameters of complex sounds. Moreover, the response selectivities for rise-fall time, duration, and AM rate could often be shown to contribute to the differential responses to complex synthetic and natural sounds.Abbreviations SON superior olivary nucleus - DMN dorsal medullary nucleus - TS torus semicircularis - FTC frequency threshold curve - BF best excitatory frequency - PAM pulsatile amplitude modulation - SAM sinusoidal amplitude modulation - SQAM square-wave amplitude modulation - MTF modulation transfer function - PSTH peri-stimulus time histogram     

Beta-Galactosidase Staining in the Nucleus of the Solitary Tract of Fos-Tau-LacZ Mice Is Unaffected by Monosodium Glutamate Taste Stimulation

Fos-Tau-LacZ (FTL) transgenic mice are used to visualize the anatomical connectivity of neurons that express c-Fos, an immediate early gene, in response to activation. In contrast to typical c-Fos protein expression, which is localized to the nucleus of stimulated neurons, activation of the c-Fos gene results in beta galactosidase (β-gal) expression throughout the entire cytoplasm of activated cells in FTL mice; thereby making it possible to discern the morphology of c-Fos expressing cells. This can be an especially important tool in brain areas in which function may be related to cell morphology, such as the primary taste/viscerosensory brainstem nucleus of the solitary tract (nTS). Thus, to further characterize FTL activity in the brain, the current study quantified both β-gal enzymatic activity as well as c-Fos protein expression in the nTS under a variety of experimental conditions (no stimulation, no stimulation with prior overnight food and water restriction, monosodium glutamate taste stimulation, and monosodium glutamate taste stimulation with perfusion 5 h post stimulation). Contrary to previous research, we found that β-gal activity (both labeled cell bodies and overall number of labeled pixels) was unchanged across all experimental conditions. However, traditional c-Fos protein activity (both cell bodies and number of activated pixels) varied significantly across experimental conditions, with the greatest amount of c-Fos protein label found in the group that received monosodium glutamate taste stimulation. Interestingly, although many c-Fos positive cells were also β-gal positive in the taste stimulated group, some c-Fos protein labeled cells were not co-labeled with β-gal. Together, these data suggest that β-gal staining within the nTS reflects a stable population of β-gal- positive neurons whose pattern of expression is unaffected by experimental condition.     

Computation of responses to color and brightness differences of neurons in the rabbit lateral geniculate nucleus

Changes in activity of 51 neurons in the rabbit lateral geniculate nucleus evoked by the replacement of eight color and eight achromatic stimuli in pairs were analyzed. It was found that neurons displayed the earliest phasic (within 50-90 ms after the replacement) and tonic response components. The earliest component strongly correlated with differences between stimuli, whereas the tonic component depended on stimuli intensity. Analysis of phasic component revealed two neuronal populations: the first group of cells was specialized for stimuli differentiation only by their intensities, and, and the second group could measure differences in colors and intensities. Neuronal perceptual spaces were reconstructed using the average of the earliest response component as a measure of differences between stimuli. Spaces of 44 neurons (86%) were two-dimensional with brightness and darkness axes. Such neurons had the same structures of space for color and achromatic stimuli. Spaces of 7 neurons (14%) were four-dimensional with two chromatic and two achromatic axes. The structures of perceptual space reconstructed from neurons in the lateral geniculate nucleus were identical to the spaces calculated from the neurons in the primary visual cortex. The structure of the perceptual space reconstructed from neuronal spikes was also similar to space calculated from the N85 visual evoked potential component recorded under similar conditions and to another space reconstructed on the basis of rabbit's instrumental learning. This fact confirmed the general principle of vector coding in the visual system. The tonic component of the most of neurons in the lateral geniculate nucleus showed a linear correlation with changes in intensities, thereby these neurons could be characterized as pre-detectors for cortical selective detectors.     

Phosphorylated KDR can be located in the nucleus of neoplastic cells

KDR （kinase insert domain receptor） phosphorylation induces several effects which lead eventually to cell proliferation and survival. The precise mechanisms by which KDR, once it is activated, communicates with the nucleus are starting to be understood but have not yet been completely unravelled. Two in vitro studies on animal cell lines reported in the literature have demonstrated that, following stimulation with VEGF, KDR is actually translocated within the nucleus. Our aim was to investigate whether this translocation occurs in human cells both in vitro and in vivo. Using laser scanning confocal microscopy, a variable nuclear localization of phosphorylated and total KDR in cell lines and tumour samples was found. In human neoplastic cell lines, hypoxic stimulation greatly increased the nuclear amount of total KDR but less so that of the phosphorylated form. Only after hypoxia and VEGF stimulation there was a comparably increased expression of phosphorylated and total KDR observed in the nuclei of these cells. We conclude that neoplastic cells show a variable expression of total and phosphorylated KDR in the nucleus. The precise functional meaning of nuclear location remains to be established.     

Oxytocin in the rat caudate nucleus influences pain modulation

Our previous studies have demonstrated that oxytocin (OXT) in the central nervous system plays a role in pain modulation. Many studies have found that caudate nucleus (CdN) enriches OXT and OXT receptors by the methods of historadioautograph and gene expression. The communication was designed to investigate OXT effect in the rat CdN on pain modulation. The results showed that (1) intra-CdN microinjection of OXT receptor antagonist, desGly-NH₂, d(CH₂)₅[d-Tyr₂, Thr-sup-4]OVT decreased the pain threshold, whereas the local administration of OXT increased the pain threshold in a dose-dependent manner; (2) OXT receptor antagonist can attenuate the analgesic role induced intra-CdN administration of OXT; and (3) pain stimulation could increase OXT concentration in the CdN perfusion liquid. The data suggested that OXT in the CdN was involved in this pain process via OXT receptors.     

Noradrenergic neurons in the rat solitary nucleus participate in the esophageal-gastric relaxation reflex

Activation of esophageal mechanosensors excites neurons in and near the central nucleus of the solitary tract (NSTc). In turn, NSTc neurons coordinate the relaxation of the stomach [i.e., the receptive relaxation reflex (RRR)] by modulating the output of vagal efferent neurons of the dorsal motor nucleus of the vagus (DMN). The NSTc area contains neurons with diverse neurochemical phenotypes, including a large population of catecholaminergic and nitrergic neurons. The aim of the present study was to determine whether either one of these prominent neuronal phenotypes was involved in the RRR. Immunohistochemical techniques revealed that repetitive esophageal distension caused 53% of tyrosine hydroxylase-immunoreactive (TH-ir) neurons to colocalize c-Fos in the NSTc. No nitric oxide synthase (NOS)-ir neurons in the NSTc colocalized c-Fos in either distension or control conditions. Local brain stem application (2 ng) of alpha-adrenoreceptor antagonists (i.e., alpha1-prazosin or alpha2-yohimbine) significantly reduced the magnitude of the esophageal distension-induced gastric relaxation to approximately 55% of control conditions. The combination of yohimbine and prazosin reduced the magnitude of the reflex to approximately 27% of control. In contrast, pretreatment with either the NOS-inhibitor NG-nitro-l-arginine methyl ester or the beta-adrenoceptor antagonist propranolol did not interfere with esophageal distension-induced gastric relaxation. Unilateral microinjections of the agonist norepinephrine (0.3 ng) directed at the DMN were sufficient to mimic the transient esophageal-gastric reflex. Our data suggest that noradrenergic, but not nitrergic, neurons of the NSTc play a prominent role in the modulation of the RRR through action on alpha1- and alpha2-adrenoreceptors. The finding that esophageal afferent stimulation alone is not sufficient to activate NOS-positive neurons in the NSTc suggests that these neurons may be strongly gated by other central nervous system inputs, perhaps related to the coordination of swallowing or emesis with respiration.