Biology subjects

Suyama, H.

Publications and source records attributed to Suyama, H..

7 recordsLinked to original sources

bioRxiv2026

Coordinated orienting behavior emerges following unilateral optogenetic activation of Superior Colliculus GABAergic neurons

Orienting coordinates movements of the eyes, whiskers, nose, and other effectors, but how the superior colliculus (SC) recruits these components over time remains unclear. We combined unilateral optogenetic activation of SC GABAergic neurons with high-speed tracking of facial movements and Neuropixels recordings to examine SC-evoked orienting in head-fixed mice. Stimulation recruited movements of the whiskers, nose, eyes, and pupil. Horizontal eye and nose movements were directed contralateral to the stimulated hemisphere, whereas vertical eye movements, pupil dilation, and whisker protraction did not differ significantly between stimulation sides. Nose and whisker movements generally preceded eye movements, followed by slower pupil dilation, revealing a temporally organized response. Recordings from the SC contralateral to the stimulated hemisphere revealed heterogeneous neuronal responses comprising short-latency excitation and delayed excitation or inhibition. Short-latency excitation was similar on trials with and without evoked movements, whereas delayed excitation was greater on trials that evoked eye or nose movements. Neurons modulated during spontaneous nose movements showed corresponding optogenetically evoked responses, linking stimulation-induced activity to endogenous movement-related activity. Thus, activation of SC GABAergic neurons initiates evolving population activity that recruits a coordinated sequence of orienting movements.

neuroscience↗

bioRxiv2025

Local olfactory nerve stimulation triggers patchy activation of columns across rat olfactory bulb

Columnar organization is a hallmark of neocortical sensory areas, most prominently in primary somatosensory and visual cortex. In the olfactory bulb, the existence of a vertical columnar organization of circuits associated with glomerular input channels has been implicated by various approaches. Here, based on activity-dependent labelling and tissue clearing, we provide direct evidence for functional bulbar columns formed by mitral cells and granule cells that display a uniform morphology.

neuroscience↗

bioRxiv2025

Synergistic olfactory nerve input and cholinergic neuromodulation can activate ERK in rat olfactory bulb vasopressin cells

Social discrimination in rats relies on vasopressin cells (VPCs) intrinsic to the olfactory bulb (OB). We had observed that VPCs responded to electrical stimulation of the olfactory nerve in acute OB slices with inhibitory postsynaptic potentials, and that the neuromodulator acetylcholine could revert these responses to excitation, resulting in action potentials (AP). Moreover, in behaving rats that were exposed to conspecifics, more VPCs were immunopositive to the neural activity marker pERK (pERK+ VPC) than in control rats. However, it is unclear whether these two observations, the increased ERK activation in vivo, and the generation of APs in the presence of ACh in vitro, can be actually mapped onto each other. Here we investigated ERK activation in acute OB slices from transgenic VP-eGFP rats upon either chemical stimulation or tetanic olfactory nerve stimulation. Both KCl and NMDA stimulation resulted in substantial pERK induction across bulbar layers and caused VPC spiking in whole-cell recordings, but only NMDA slightly increased pERK+ VPC percentage. Tetanic olfactory nerve stimulation yielded localized, column-like ERK activation of neurons across bulbar layers. The presence of ACh during tetanic stimulation substantially and specifically increased percentages of pERK+ VPCs within columns, indicating that columnar pERK+ VPCs were preferentially activated by coincident cholinergic neuromodulation and synaptic input. Our results validate pERK induction as a tool to monitor synaptic VPC excitation in the OB, and imply that depolarization of VPCs alone is insufficient to activate ERK. We propose that synaptically evoked APs are a prerequisite for pERK induction in VPCs.

neuroscience↗

bioRxiv2024

Vasopressin differentially modulates the excitability of rat olfactory bulb neuron subtypes

Vasopressin (VP) is essential for social memory already at the level of the olfactory bulb (OB), and OB VP cells are activated by social interaction. However, it remains unclear how VP modulates olfactory processing to enable enhanced discrimination of very similar odors, e.g., rat body odors. So far, it has been shown that VP reduces firing rates in mitral cells (MCs) during odor presentation in-vivo and decreases the amplitudes of olfactory nerve-evoked excitatory postsynaptic potentials (ON-evoked EPSPs) in external tufted cells in-vitro. We performed whole-cell patch-clamp recordings and population Ca2+ imaging on acute rat OB slices. We recorded ON-evoked EPSPs as well as spontaneous inhibitory postsynaptic currents (IPSCs) from two types of projection neurons, middle tufted cells (mTCs) and MCs. VP bath-application reduced the amplitudes of ON-evoked EPSPs and the frequencies of spontaneous IPSCs in mTCs but did not change those in MCs. Therefore, we analyzed ON evoked-EPSPs in inhibitory interneurons, i.e., periglomerular cells (PGCs) and granule cells (GCs), to search for the origin of increased inhibition in mTCs. However, VP did not increase the amplitudes of evoked EPSPs in either type of interneurons. We next performed two-photon population Ca2+ imaging in the glomerular layer and the superficial GC layer of responses to stronger ON stimulation than during patch-clamp experiments that should evoke action potentials in the measured cells. We observed that VP application increased ON-evoked Ca2+ influx in juxtaglomerular cell and GC somata and decreased it in the intraglomerular neuropil. Thus, our findings indicate inhibition by VP on projection neurons via strong ON input-mediated inhibitory interneuron activity.

neuroscience↗

bioRxiv2024

Proteomic comparison of epidemic Australian Bordetella pertussis biofilm cells

Bordetella pertussis causes whooping cough, a severe respiratory infectious disease. Studies have compared the currently dominant single nucleotide polymorphism (SNP) cluster I (pertussis toxin promoter allele, ptxP3) and previously dominant SNP cluster II (ptxP1) strains as planktonic cells. Since biofilm formation is linked with B. pertussis pathogenesis in vivo, this study compared the biofilm formation capabilities of representative strains of cluster I and cluster II. Confocal laser scanning microscopy found that the cluster I strain had a denser biofilm structure compared to the cluster II strain. Differences in protein expression of the biofilm cells were then compared using Tandem Mass Tagging (TMT) and high-resolution multiple reaction monitoring (MRM-hr). In total, 1453 proteins were identified of which 40 proteins had significant differential expression between the two strains in biofilm conditions. Of particular interest was a large increase in expression of energy metabolism proteins (cytochrome proteins PetABC and BP3650) in the cluster I strain. When the expression of these proteins was compared between 6 additional strains from each cluster, it was found that the protein expression varied between all strains. These findings suggest that there are large levels of individual proteomic diversity between B. pertussis strains in biofilm conditions despite the highly conserved genome of the species. Overall, this study revealed visual differences in biofilm structure between B. pertussis strains and highlighted strain specific variation in protein expression that dominate potential cluster specific changes that may be linked with the dominance of cluster I strains. ImportanceBordetella pertussis causes whooping cough. The currently circulating cluster I strains have taken over previously dominant cluster II strains. It is important to understand the reasons behind the evolution to develop new strategies against the pathogen. Recent studies have shown that B. pertussis can form biofilms during infection. This study compared the biofilm formation capabilities of a cluster I and a cluster II strain and identified visual differences in the biofilms. The protein expression between these strains grown in biofilms were compared and proteins identified with varied expression were measured with additional strains from each cluster. It was found that despite the highly conserved genetics of the species, there was varied protein expression between the additional strains. This study highlights that strain specific variation in protein expression during biofilm conditions that may dominate the cluster specific changes that may be linked to the dominance of cluster I strains.

microbiology↗

bioRxiv2022

Integrating proteomic data with metabolic modelling provides insight into key pathways of Bordetella pertussis biofilms

Pertussis, commonly known as whooping cough is a severe respiratory disease caused by the bacterium, Bordetella pertussis. Despite widespread vaccination, pertussis resurgence has been observed globally. The development of the current acellular vaccine (ACV) has been based on planktonic studies. However, recent studies have shown that B. pertussis readily forms biofilms. A better understanding of B. pertussis biofilms is important for developing novel vaccines that can target all aspects of B. pertussis infection. This study compared the proteomic expression of biofilm and planktonic B. pertussis cells to identify key changes between the conditions. Major differences were identified in virulence factors including an upregulation of toxins (adenylate cyclase toxin and dermonecrotic toxin) and downregulation of pertactin and type III secretion system proteins in biofilm cells. To further dissect metabolic pathways that are altered during the biofilm lifestyle, the proteomic data was then incorporated into a genome scale metabolic model using the integrative metabolic analysis tool (iMAT). The analysis revealed that planktonic cells utilised the glyoxylate shunt while biofilm cells completed the full tricarboxylic acid cycle. Differences in processing aspartate, arginine and alanine were identified as well as unique export of valine out of biofilm cells which may have a role in inter-bacterial communication and regulation. Finally, increased polyhydroxybutyrate accumulation and superoxide dismutase activity in biofilm cells may contribute to increased persistence during infection. Taken together, this study modelled major proteomic and metabolic changes that occur in biofilm cells which helps lay the groundwork for further understanding B. pertussis pathogenesis.

microbiology↗

bioRxiv2020

Top-down acetylcholine enables social discrimination via unlocking action potential generation in olfactory bulb vasopressin cells

Social discrimination in rats requires activation of the intrinsic bulbar vasopressin system, but it is unclear how this system comes into operation, as olfactory nerve stimulation primarily inhibits bulbar vasopressin cells (VPCs). Here we show that stimulation with a conspecific can activate bulbar VPCs, indicating that VPC activation depends on more than olfactory cues during social interaction. A series of in-vitro electrophysiology, pharmacology and immunohistochemistry experiments implies that acetylcholine probably originating from centrifugal projections can enable olfactory nerve-evoked action potentials in VPCs. Finally, cholinergic activation of the vasopressin system contributes to vasopressin-dependent social discrimination, since recognition of a known rat was blocked by bulbar infusion of the muscarinic acetylcholine receptor antagonist atropine and rescued by additional bulbar application of vasopressin. Thus, we demonstrated that top-down cholinergic modulation of bulbar VPC activity is involved in social discrimination in rats.

neuroscience↗