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  • C1 neurons excite locus coeruleus and A5 noradrenergic neurons along with sympathetic outflow in rats. 22526887

    C1 neurons activate sympathetic tone and stimulate the hypothalamic–pituitary–adrenal axis in circumstances such as pain, hypoxia or hypotension. They also innervate pontine noradrenergic cell groups, including the locus coeruleus (LC) and A5. Activation of C1 neurons reportedly inhibits LC neurons; however, because these neurons are glutamatergic and have excitatory effects elsewhere, we re-examined the effect of C1 activation on pontine noradrenergic neurons (LC and A5) using a more selective method. Using a lentivirus that expresses channelrhodopsin2 (ChR2) under the control of the artificial promoter PRSx8, we restricted ChR2 expression to C1 neurons (67%), retrotrapezoid nucleus neurons (20%) and cholinergic neurons (13%). The LC contained ChR2-positive terminals that formed asymmetric synapses and were immunoreactive for vesicular glutamate transporter type 2. Low-frequency photostimulation of ChR2-expressing neurons activated LC (38 of 65; 58%) and A5 neurons (11 of 16; 69%) and sympathetic nerve discharge. Locus coeruleus and A5 inhibition was not seen unless preceded by excitation. Locus coeruleus activation was eliminated by intracerebroventricular kynurenic acid. Stimulation of ChR2-expressing neurons at 20 Hz produced modest increases in LC and A5 neuronal discharge. In additional rats, the retrotrapezoid nucleus region was destroyed with substance P–saporin prior to lentivirus injection into the rostral ventrolateral medulla, increasing the proportion of C1 ChR2-expressing neurons (83%). Photostimulation in these rats activated the same proportion of LC and A5 neurons as in control rats but produced no effect on sympathetic nerve discharge owing to the destruction of bulbospinal C1 neurons. In conclusion, low-frequency stimulation of C1 neurons activates pontine noradrenergic neurons and sympathetic nerve discharge, possibly via the release of glutamate from monosynaptic C1 inputs.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Cholinergic neurons excite cortically projecting basal forebrain GABAergic neurons. 24553925

    The basal forebrain (BF) plays an important role in the control of cortical activation and attention. Understanding the modulation of BF neuronal activity is a prerequisite to treat disorders of cortical activation involving BF dysfunction, such as Alzheimer's disease. Here we reveal the interaction between cholinergic neurons and cortically projecting BF GABAergic neurons using immunohistochemistry and whole-cell recordings in vitro. In GAD67-GFP knock-in mice, BF cholinergic (choline acetyltransferase-positive) neurons were intermingled with GABAergic (GFP(+)) neurons. Immunohistochemistry for the vesicular acetylcholine transporter showed that cholinergic fibers apposed putative cortically projecting GABAergic neurons containing parvalbumin (PV). In coronal BF slices from GAD67-GFP knock-in or PV-tdTomato mice, pharmacological activation of cholinergic receptors with bath application of carbachol increased the firing rate of large (greater than 20 μm diameter) BF GFP(+) and PV (tdTomato+) neurons, which exhibited the intrinsic membrane properties of cortically projecting neurons. The excitatory effect of carbachol was blocked by antagonists of M1 and M3 muscarinic receptors in two subpopulations of BF GABAergic neurons [large hyperpolarization-activated cation current (Ih) and small Ih, respectively]. Ion substitution experiments and reversal potential measurements suggested that the carbachol-induced inward current was mediated mainly by sodium-permeable cation channels. Carbachol also increased the frequency of spontaneous excitatory and inhibitory synaptic currents. Furthermore, optogenetic stimulation of cholinergic neurons/fibers caused a mecamylamine- and atropine-sensitive inward current in putative GABAergic neurons. Thus, cortically projecting, BF GABAergic/PV neurons are excited by neighboring BF and/or brainstem cholinergic neurons. Loss of cholinergic neurons in Alzheimer's disease may impair cortical activation, in part, through disfacilitation of BF cortically projecting GABAergic/PV neurons.
    Document Type:
    Reference
    Product Catalog Number:
    AB143
    Product Catalog Name:
    Anti-Choline Acetyltransferase (ChAT) Antibody

  • Identified motoneurons involved in sexual and eliminative functions in the rat are powerfully excited by vasopressin and tachykinins. 17050711

    The pudendal motor system is constituted by striated muscles of the pelvic floor and the spinal motoneurons that innervate them. It plays a role in eliminative functions of the bladder and intestine and in sexual function. Pudendal motoneurons are located in the ventral horn of the caudal lumbar spinal cord and send their axon into the pudendal nerve. In the rat, binding sites for vasopressin and tachykinin are present in the dorsomedial and dorsolateral pudendal nuclei, suggesting that these neuropeptides may affect pudendal motoneurons. The aim of the present study was to investigate possible effects of vasopressin and tachykinins on these motoneurons. Recordings were performed in spinal cord slices of young male rats using the whole-cell patch-clamp technique. Before recording, motoneurons were identified by 1,1'-dilinoleyl-3,3,3',3'-tetramethylindocarbocyanine, 4-chlorobenzenesulfonate retrograde labeling. The identification was confirmed, a posteriori, by choline acetyltransferase immunocytochemistry. Vasopressin and tachykinins caused a powerful excitation of pudendal motoneurons. The peptide-evoked depolarization, or the peptide-evoked inward current, persisted in the presence of tetrodotoxin, indicating that these effects were mainly postsynaptic. By using selective receptor agonists and antagonist, we determined that vasopressin acted via vasopressin 1a (V1a), but not V1b, V2, or oxytocin receptors, whereas tachykinins acted via neurokinin 1 (NK1), but not NK2 or NK3, receptors. Vasopressin acted by enhancing a nonselective cationic conductance; in some motoneurons, it also probably suppressed a resting K+ conductance. Our data show that vasopressin and tachykinins can excite pudendal motoneurons and thus influence the force of striated perineal muscles involved in eliminative and sexual functions.
    Document Type:
    Reference
    Product Catalog Number:
    AB144P
    Product Catalog Name:
    Anti-Choline Acetyltransferase Antibody

  • ANANDAMIDE MODULATES CAROTID SINUS NERVE AFFERENT ACTIVITY VIA TRPV1 RECEPTORS INCREASING RESPONSES TO HEAT. 21903882

    Abnormal respiratory chemosensitivity is implicated in recurrent apnoea syndromes, with the peripheral chemoreceptors, the carotid bodies, playing a particularly important role. Previous work suggests supraphysiological concentrations of the endocannabinoid, endovanilloid and TASK-channel blocker anandamide (ANA) excite carotid bodies, but the mechanism(s) and physiological significance are unknown. Given carotid body output is temperature sensitive, we hypothesized ANA stimulates carotid body chemosensory afferents via temperature-sensitive vanilloid (TRPV1) receptors. To test this, we used the dual-perfused in situ rat preparation to confirmed that independent perfusion of carotid arteries with supra-physiological concentrations of ANA strongly excite carotid sinus nerve afferents and this activity is sufficiently to increase phrenic activity. Next, using ex vivo carotid body preparations we demonstrate these effects are mediated by TRPV1, not CB1 receptors nor TASK channels: in CB1-null mouse preparations, ANA increased afferent activity across all levels of PO(2), whereas in TRPV1-null mouse preparations, the stimulatory effect of ANA was absent. In rat ex vivo preparations, ANA\'s stimulatory effects were mimicked by olvanil, a non-pungent TRPV1 agonist, and suppressed by TRPV1 antagonist AMG9810. The specific CB1 agonist oleamide had no effect. Physiological levels of ANA had no effect alone, but increased sensitivity to mild hyperthermia. AMG9810 blocked ANA\'s effect on temperature response. Immuno-labelling and RT-PCR demonstrated TRPV1 receptors are not expressed in carotid body glomus cells but reside in petrosal sensory afferents. Together, these results suggest ANA plays a physiological role in augmenting afferent responses to mild hyperthermia by activating TRPV1 receptors on petrosal afferents.
    Document Type:
    Reference
    Product Catalog Number:
    AB1542
    Product Catalog Name:
    Anti-Tyrosine Hydroxylase Antibody

  • Exercise reduces GABA synaptic input onto nucleus tractus solitarii baroreceptor second-order neurons via NK1 receptor internalization in spontaneously hypertensive rats. 19261870

    A single bout of mild to moderate exercise can lead to a postexercise decrease in blood pressure in hypertensive subjects, namely postexercise hypotension (PEH). The full expression of PEH requires a functioning baroreflex, hypertension, and activation of muscle afferents (exercise), suggesting that interactions in the neural networks regulating exercise and blood pressure result in this fall in blood pressure. The nucleus tractus solitarii (NTS) is the first brain site that receives inputs from nerves carrying blood pressure and muscle activity information, making it an ideal site for integrating cardiovascular responses to exercise. During exercise, muscle afferents excite NTS GABA neurons via substance P and microinjection of a substance P-neurokinin 1 receptor (NK1-R) antagonist into the NTS attenuates PEH. The data suggest that an interaction between the substance P NK1-R and GABAergic transmission in the NTS may contribute to PEH. We performed voltage clamping on NTS baroreceptor second-order neurons in spontaneously hypertensive rats (SHRs). All animals were killed within 30 min and the patch-clamp recordings were performed 2-8 h after the sham/exercise protocol. The data showed that a single bout of exercise reduces (1) the frequency but not the amplitude of GABA spontaneous IPSCs (sIPSCs), (2) endogenous substance P influence on sIPSC frequency, and (3) sIPSC frequency response to exogenous application of substance P. Furthermore, immunofluorescence labeling in NTS show an increased substance P NK1-R internalization on GABA neurons. The data suggest that exercise-induced NK1-R internalization results in a reduced intrinsic inhibitory input to the neurons in the baroreflex pathway.
    Document Type:
    Reference
    Product Catalog Number:
    Multiple
    Product Catalog Name:
    Multiple

  • Demonstration of true-color high-contrast microorganism imaging for terbium bioprobes. 21448978

    Lanthanide bioprobes offer a number of novel advantages for advanced cytometry, including the microsecond luminescence lifetime, sharp spectral emission, and large stokes shift. However, to date, only the europium-based bioprobes have been broadly studied for time-gated luminescence cell imaging, though a wide range of efficient terbium bioprobes have been synthesized and some of them are commercially available. We analyze that the bottleneck problem was due to the lack of an efficient microscope with pulsed excitation at wavelengths of 300-330 nm. We investigate a recently available 315 nm ultraviolet (UV) light emitting diode to excite an epifluorescence microscope. Substituting a commercial UV objective (40×), the 315 nm light efficiently delivered the excitation light onto the uncovered specimen. A novel pinhole-assisted optical chopper unit was attached behind the eyepiece for direct lifetime-gating to permit visual inspection of background-free images. We demonstrate the use of a commercial terbium complex for high-contrast imaging of an environmental pathogenic microorganism, Cryptosporidium parvum. As a result of effective autofluorescence suppression by a factor of 61.85 in the time domain, we achieved an enhanced signal-to-background ratio of 14.43. This type of time-gating optics is easily adaptable to the use of routine epifluorescence microscopes, which provides an opportunity for high-contrast imaging using multiplexed lanthanide bioprobes.
    Document Type:
    Reference
    Product Catalog Number:
    AP200B
    Product Catalog Name:
    Goat Anti-Mouse light chain Antibody, biotin conjugate

  • Immunocytochemical evidence that collision sensing neurons in the locust visual system contain acetylcholine. 10870080

    The lobula giant movement detector (LGMD1 and -2) neurons in the locust visual system are parts of motion-sensitive pathways that detect objects approaching on a collision course. The dendritic processes of the LGMD1 and -2 in the lobula are localised to discrete regions, allowing the dendrites of each neuron to be distinguished uniquely. As was described previously for the LGMD1, the afferent processes onto the LGMD2 synapse directly with each other, and these synapses are immediately adjacent to their outputs onto the LGMD2. Here we present immunocytochemical evidence, using antibodies against choline-protein conjugates and a polyclonal antiserum against choline acetyltransferase (ChAT; Chemicon Ab 143), that the LGMD1 and -2 and the retinotopic units presynaptic to them contain acetylcholine (ACh). It is proposed that these retinotopic units excite the LGMD1 or -2 but inhibit each other. It is well established that ACh has both excitatory and inhibitory effects and may provide the substrate for a critical race in the LGMD1 or -2, between excitation caused by edges moving out over successive photoreceptors, and inhibition spreading laterally resulting in the selective response to objects approaching on a collision course. In the optic lobe, ACh was also found to be localised in discrete layers of the medulla and in the outer chiasm between the lamina and medulla. In the brain, the antennal lobes contained neurons that reacted positively for ACh. Silver- or haematoxylin and eosin-stained sections through the optic lobe confirmed the identities of the positively immunostained neurons.
    Document Type:
    Reference
    Product Catalog Number:
    AB143
    Product Catalog Name:
    Anti-Choline Acetyltransferase (ChAT) Antibody

  • Dopamine D4 receptor excitation of lateral habenula neurons via multiple cellular mechanisms. 24155292

    Glutamatergic lateral habenula (LHb) output communicates negative motivational valence to ventral tegmental area (VTA) dopamine (DA) neurons via activation of the rostromedial tegmental nucleus (RMTg). However, the LHb also receives a poorly understood DA input from the VTA, which we hypothesized constitutes an important feedback loop regulating DA responses to stimuli. Using whole-cell electrophysiology in rat brain slices, we find that DA initiates a depolarizing inward current (I(DAi)) and increases spontaneous firing in 32% of LHb neurons. I(DAi) was also observed upon application of amphetamine or the DA uptake blockers cocaine or GBR12935, indicating involvement of endogenous DA. I(DAi) was blocked by D4 receptor (D4R) antagonists (L745,870 or L741,742), and mimicked by a selective D4R agonist (A412997). I(DAi) was associated with increased whole-cell conductance and was blocked by Cs+ or a selective blocker of hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channel, ZD7288. I(DAi) was also associated with a depolarizing shift in half-activation voltage for the hyperpolarization-activated cation current (Ih) mediated by HCN channels. Recordings from LHb neurons containing fluorescent retrograde tracers revealed that I(DAi) was observed only in cells projecting to the RMTg and not the VTA. In parallel with direct depolarization, DA also strongly increased synaptic glutamate release and reduced synaptic GABA release onto LHb cells. These results demonstrate that DA can excite glutamatergic LHb output to RMTg via multiple cellular mechanisms. Since the RMTg strongly inhibits midbrain DA neurons, activation of LHb output to RMTg by DA represents a negative feedback loop that may dampen DA neuron output following activation.
    Document Type:
    Reference
    Product Catalog Number:
    MAB318
    Product Catalog Name:
    Anti-Tyrosine Hydroxylase Antibody, clone LNC1