Figure 1 - uploaded by Tetsuya Tatsukawa
Content may be subject to copyright.
Immunostaining for motilin receptors in the medial vestibular nucleus and cerebellar flocculus. (A) Image of brainstem slice (thickness, 300 μm) obtained from a wild-type mouse. (B) An example of a patch-clamped motilin-sensitive neuron labeled by lucifer yellow. Lucifer yellow was added to the pipette solution. (C) A photograph of a neuron in the rostral parvocellular part of the medial vestibular nucleus (MVNpc) (marked by arrow) labeled by anti-motilin receptor antibody. (D) Image of four floccular Purkinje cells (marked by arrows) labeled by anti-motilin receptor antibody. (E) Low-magnification view of the flocculus. The labeled Purkinje cells in D are observed in the area marked by the dotted rectangle. (F) Western blot analysis of the anti-motilin receptor antibody. S, standard marker (Precision Plus protein prestained standard, Bio-Rad). Lanes: 1, not treated with motilin; treated with: 2, 0.001 μm motilin; 3, 0.01 μm motilin; 4, 0.03 μm motilin; 5, 0.1 μm motilin; 6, 0.3 μm motilin; and 7, 1 μm motilin. The molecular weight of motilin is approximately 45 kD, and that of the anti-motilin receptor antibody is 15 kD (see arrow). BS, brainstem; FL, flocculus; MVNmc, magnocellular part of the medial vestibular nucleus; PFL, paraflocculus; Pr, prepositus hypoglossal nucleus; 4V, fourth ventricle. Scale bars: 200 μm (A and E) and 20 μm (B, C, and D).
Source publication
Some central nervous system neurons express receptors of gastrointestinal hormones, but their pharmacological actions are not well known. Previous anatomical and unit recording studies suggest that a group of cerebellar Purkinje cells express motilin receptors, and motilin depresses the spike discharges of vestibular nuclear neurons that receive di...
Contexts in source publication
Context 1
... diethyl ether anesthesia, mice were decapitated and brainstem slices (thickness, 300 lm) containing the medial vestibular nucleus (Fig. 1A) were prepared in the oblique coronal plane using a vibra- tome (VT1000S, Leica Microsystems, Wetzlar, Germany) with a micrograin carbide blade (FW35, Kyocera, Kyoto, Japan) in an ice- cold solution containing (in mM here and hereafter, unless otherwise indicated): 210 sucrose, 2.5 KCl, 2 CaCl 2 , 1 MgSO 4 , 1.25 NaH 2 PO 4 , 26 NaHCO 3 ...
Context 2
... were placed in the recording chamber and continuously per- fused (2 mL/min) with the O 2 and CO 2 gas-equilibrated ACSF at 28 ° C. MVNs were visualised directly (Fig. 1B) under an infrared differ- ential interference contrast microscope (BX51WL, Olympus, Tokyo, Japan). Patch pipettes (resistance, 3-4 MΩ) were pulled using a P97 puller (Sutter Instrument, Novato, CA, USA) from borosilicate glass (GC150F-10, Harvard Apparatus, Kent, UK). Whole-cell patch-clamp recording was performed on MVNs using ...
Context 3
... incubated overnight with 0.001, 0.01, 0.03, 0.1, 0.3, or 1 lM motilin at 4 °C. These seven fractions were then treated with the Laemmli sample buffer (Bio-Rad Labora- tories, Hercules, CA, USA) and 2-mercaptoethanol, boiled at 100 ° C for 5 min, and subjected to sodium dodecyl sulfate-polyacryl- amide gel electrophoresis for western blot analysis (Fig. 1F). Preci- sion Plus Protein Standard (Bio-Rad Japan, Tokyo) was used as the standard ...
Context 4
... recorded spontaneous APs and IPSCs of MVNs in brainstem slices obtained from C57BL/6J and VGAT-Venus transgenic mice (Fig. 1A). We applied motilin to the recording chamber and examined its effects on APs and IPSCs. Significant motilin effects on APs and IPSCs were observed in the relatively large MVNs (soma diameter, 15 -25 lm; Fig. 1B), which were mainly located in the middle of the parvocellular part of the rostral medial vestibular nucleus (Franklin & ...
Context 5
... recorded spontaneous APs and IPSCs of MVNs in brainstem slices obtained from C57BL/6J and VGAT-Venus transgenic mice (Fig. 1A). We applied motilin to the recording chamber and examined its effects on APs and IPSCs. Significant motilin effects on APs and IPSCs were observed in the relatively large MVNs (soma diameter, 15 -25 lm; Fig. 1B), which were mainly located in the middle of the parvocellular part of the rostral medial vestibular nucleus (Franklin & Paxinos, 1997). Neurons with a small soma (diameter, 5-15 lm) in the parvocellular part, or those in the mediocaudal part were not moti- lin-sensitive. We immunohistologically located motilin-receptor- expressing ...
Citations
... LMVN GABAergic neurons exhibited spontaneous firing at a regular frequency (Figure 1), consistent with previous reports using the MVN slices. [92][93][94] Thus, there might not be much difference between LMVN GABAertgic neurons and most Suppression of LMVN GABAergic neurons did not cause large changes in walking, posture of sleep, and head movement (Videos S1 and S2, and Figure S4), which is consistent with a recent optogenetic study: activation of GABAergic neurons in the vestibular nuclei does not contribute to postural maintenance. 99 Thus, unlike other types of MVN neurons, LMVN GABAergic neurons may not actively affect vestibular functions in freely moving conditions without specific strong or prolonged vestibular stimuli. ...
Body rocking can either induce sleep or arousal. That is, the vestibular sense influences sleep-wake states. Neuronal interactions between sleep-wake systems and vestibular systems, however, remain unclear. In this study, we found that GABAergic neurons in the lateral part of the medial vestibular nucleus (LMVN), a primary vestibular afferent projection site, control sleep-wake states. Specific inhibition of LMVN GABAergic neurons revealed that the firing of LMVN GABAergic neurons underlies stable wakefulness and smooth transitions from non-rapid-eye-movement (NREM) sleep to rapid eye movement (REM) sleep and that LMVN GABAergic neurons do not affect body balance control in freely moving conditions. Selective axonal tracing of LMVN GABAergic neurons indicated that LMVN GABAergic neurons send axons not only to areas involved in vestibular and oculomotor functions but also to areas regulating sleep-wake states. Our findings suggest that LMVN GABAergic neurons stabilize wakefulness and gate the entry into REM sleep through the use of vestibular information.
... Motilin receptors have also been identified in other brain regions that have been implicated in the pathophysiology of depression [116], such as the hippocampus and hypothalamus [117,118]. Motilin receptors have also been identified in the cerebellum [119], which has been implicated in the pathophysiology of recurrent depressive episodes [120]. In all these brain regions, motilin may act to enhance GABAergic neurotransmission. ...
Recent research has identified the gut–brain axis as a key mechanistic pathway and potential therapeutic target in depression. In this paper, the potential role of gut hormones as potential treatments or predictors of response in depression is examined, with specific reference to the peptide hormone motilin. This possibility is explored through two methods: (1) a conceptual review of the possible links between motilin and depression, including evidence from animal and human research as well as clinical trials, based on a literature search of three scientific databases, and (2) an analysis of the relationship between a functional polymorphism (rs2281820) of the motilin (MLN) gene and cross-national variations in the prevalence of depression based on allele frequency data after correction for potential confounders. It was observed that (1) there are several plausible mechanisms, including interactions with diet, monoamine, and neuroendocrine pathways, to suggest that motilin may be relevant to the pathophysiology and treatment of depression, and (2) there was a significant correlation between rs2281820 allele frequencies and the prevalence of depression after correcting for multiple confounding factors. These results suggest that further evaluation of the utility of motilin and related gut peptides as markers of antidepressant response is required and that these molecular pathways represent potential future mechanisms for antidepressant drug development.
... Our previous studies of mouse HOKR demonstrated that the blockade of protein synthesis during training by bilateral floccular applications of anisomycin or actinomycin D [9], or the shutdown of spontaneous FL P-cell activity during post-training periods by bilateral floccular applications of muscimol [73] impaired the formation of long-term memory of adaptation in MVN. Moreover, two electrophysiological experiments using rabbit in-vivo [74] and mouse brainstem slice [75] preparations consistently suggested that the peptide hormone, motilin, may be coreleased with GABA from P-cell axon terminals in vestibular nuclei to modulate the excitability of postsynaptic nuclear neurons. On the basis of these observations, we suggest that some proteins or peptides, which are synthesized in FL P-cells during training, may be transferred to MVN through the axonal transport, and released to induce the plasticity in excitatory synapses on MVN neurons [70][71][72]75], which underlies the long-term memory of adaptation [8]. ...
... Moreover, two electrophysiological experiments using rabbit in-vivo [74] and mouse brainstem slice [75] preparations consistently suggested that the peptide hormone, motilin, may be coreleased with GABA from P-cell axon terminals in vestibular nuclei to modulate the excitability of postsynaptic nuclear neurons. On the basis of these observations, we suggest that some proteins or peptides, which are synthesized in FL P-cells during training, may be transferred to MVN through the axonal transport, and released to induce the plasticity in excitatory synapses on MVN neurons [70][71][72]75], which underlies the long-term memory of adaptation [8]. Although further studies are necessary to examine whether such a scenario is possible or not, the very short distance between the inhibitory synapses and the excitatory synapses (mean, 0.136 μm; Fig 6) on the distal dendrites of parvocellular MVN/PrH neurons may be favorable for the diffusion of such proteins from P-cell inhibitory synapses to excitatory synapses. ...
Adaptations of vestibulo-ocular and optokinetic response eye movements have been studied as an experimental model of cerebellum-dependent motor learning. Several previous physiological and pharmacological studies have consistently suggested that the cerebellar flocculus (FL) Purkinje cells (P-cells) and the medial vestibular nucleus (MVN) neurons targeted by FL (FL-targeted MVN neurons) may respectively maintain the memory traces of short- and long-term adaptation. To study the basic structures of the FL-MVN synapses by light microscopy (LM) and electron microscopy (EM), we injected green florescence protein (GFP)-expressing lentivirus into FL to anterogradely label the FL P-cell axons in C57BL/6J mice. The FL P-cell axonal boutons were distributed in the magnocellular MVN and in the border region of parvocellular MVN and prepositus hypoglossi (PrH). In the magnocellular MVN, the FL-P cell axons mainly terminated on somata and proximal dendrites. On the other hand, in the parvocellular MVN/PrH, the FL P-cell axonal synaptic boutons mainly terminated on the relatively small-diameter (< 1 μm) distal dendrites of MVN neurons, forming symmetrical synapses. The majority of such parvocellular MVN/PrH neurons were determined to be glutamatergic by immunocytochemistry and in-situ hybridization of GFP expressing transgenic mice. To further examine the spatial relationship between the synapses of FL P-cells and those of vestibular nerve on the neurons of the parvocellular MVN/PrH, we added injections of biotinylated dextran amine into the semicircular canal and anterogradely labeled vestibular nerve axons in some mice. The MVN dendrites receiving the FL P-cell axonal synaptic boutons often closely apposed vestibular nerve synaptic boutons in both LM and EM studies. Such a partial overlap of synaptic boutons of FL P-cell axons with those of vestibular nerve axons in the distal dendrites of MVN neurons suggests that inhibitory synapses of FL P-cells may influence the function of neighboring excitatory synapses of vestibular nerve in the parvocellular MVN/PrH neurons.
The gastrointestinal (GI) hormone motilin helps control human stomach movements during hunger and promotes hunger. Although widely present among mammals, it is generally accepted that in rodents the genes for motilin and/or its receptor have undergone pseudonymization, so exogenous motilin cannot function. However, several publications describe functions of low concentrations of motilin, usually within the GI tract and CNS of mice, rats, and guinea pigs. These animals were from institute‐held stocks, simply described with stock names (e.g., “Sprague–Dawley”) or were inbred strains. It is speculated that variation in source/type of animal introduces genetic variations to promote motilin‐sensitive pathways. Perhaps, in some populations, motilin receptors exist, or a different functionally‐active receptor has a good affinity for motilin (indicating evolutionary pressures to retain motilin functions). The ghrelin receptor has the closest sequence homology, yet in non‐rodents the receptors have a poor affinity for each other's cognate ligand. In rodents, ghrelin may substitute for certain GI functions of motilin, but no good evidence suggests rodent ghrelin receptors are highly responsive to motilin. It remains unknown if motilin has functional relationships with additional bioactive molecules formed from the ghrelin and motilin genes, or if a 5‐TM motilin receptor has influence in rodents (e.g., to dimerize with GPCRs and create different pharmacological profiles). Is the absence/presence of responses to motilin in rodents’ characteristic for systems undergoing gene pseudonymization? What are the consequences of rodent supplier‐dependent variations in motilin sensitivity (or other ligands for receptors undergoing pseudonymization) on gross physiological functions? These are important questions for understanding animal variation.
The Marr–Albus–Ito cerebellar learning hypothesis proposed around 1970 has been tested by analyzing how the cerebellar flocculus (FL) induces adaptations in the horizontal vestibulo-ocular (HVOR) and optokinetic reflex (HOKR) eye movements through the synapse plasticity of Purkinje cells (PCs). In 1982, Ito’s group discovered the long-term depression (LTD) at parallel fiber (PF)–PC synapses by conjunctive electrical stimulation of PFs with climbing fibers (CFs). Many lines of experimental evidence using various methods and materials have supported the hypothesis. Today, the hypothesis is considered as a fundamental mechanism of cerebellar learning. Furthermore, it was found that after repetition of adaptations, the memory of adaptation is transferred from FL to the vestibular nuclei (VN) targeted by FL for consolidation through the plasticity of VN neurons. After overviewing the hypothesis, I discuss roles of multiple cerebellar plasticity in ocular reflex adaptations and the application of the hypothesis to integrative brain functions.
Masao Ito proposed a cerebellar learning hypothesis with Marr and Albus in the early 1970s. He suggested that cerebellar flocculus Purkinje cells (PCs), which directly inhibit the vestibular nuclear neurons driving extraocular muscle motor neurons, adaptively control the horizontal vestibulo-ocular reflex (HVOR) through the modification of mossy and parallel fiber-mediated vestibular responsiveness by visual climbing fiber inputs. Later, it was suggested that the same flocculus PCs adaptively control the horizontal optokinetic response (HOKR) in the same manner through the modification of optokinetic responsiveness in rodents and rabbits. In 1982, Ito and his colleagues discovered the plasticity of long-term depression (LTD) at parallel fiber (PF)–PC synapses after conjunctive stimulation of mossy or parallel fibers with climbing fibers. Long-term potentiation (LTP) at PF–PC synapses by weak PF stimulation alone was found later. Many lines of experimental evidence have supported their hypothesis using various experimental methods and materials for the past 50 years by many research groups. Although several controversial findings were presented regarding their hypothesis, the reasons underlying many of them were clarified. Today, their hypothesis is considered as a fundamental mechanism of cerebellar learning. Furthermore, it was found that the memory of adaptation is transferred from the flocculus to vestibular nuclei for consolidation by repetition of adaptation through the plasticity of vestibular nuclear neurons. In this article, after overviewing their cerebellar learning hypothesis, I discuss possible roles of LTD and LTP in gain-up and gain-down HVOR/HOKR adaptations and refer to the expansion of their hypothesis to cognitive functions.
