Biology subjects

Baker, A. L.

Publications and source records attributed to Baker, A. L..

14 recordsLinked to original sources

bioRxiv2026

A multivalent mRNA-lipid nanoparticle vaccine containing eight hemagglutinin antigens elicited broad neutralizing antibody responses and protected against influenza A virus challenge in swine.

The diversity within H1 and H3 subtype influenza A viruses (IAV) in swine prevents effective vaccine control approaches with inactivated whole-virus vaccines. We addressed the challenge of controlling co-circulating hemagglutinin (HA) clades of swine IAV with the development of a multivalent mRNA-lipid nanoparticle (LNP) vaccine expressing 8 HA proteins to maximize genetic coverage. We applied a computational approach to select eight HA genes that represented 95% of the observed IAV detected in the United States between 2022 and 2025. Piglets were vaccinated and boosted intramuscularly with either individual HA mRNA-LNP or an 8-HA multivalent mRNA-LNP. Serum was collected to evaluate systemic antibody levels. Twenty-one days post-boost, pigs were challenged with a field relevant H1 1A.3.3.3-c3 IAV strain. The 8-HA multivalent mRNA-LNP vaccine induced neutralizing antibodies against all eight antigens and vaccinees were protected against lung lesions, with lesion scores similar to non-challenged animals. Homologous monovalent vaccination significantly reduced IAV detection in nasal secretions and in the lungs. Heterologous monovalent vaccination was not cross-protective but did not induce vaccine-associated enhanced respiratory disease. We provide evidence that monovalent and multivalent mRNA-LNP influenza vaccines elicited neutralizing antibody responses in pigs and protected against viral challenge. The versatility and capacity for rapidly updating the mRNA-LNP vaccine platform make it an appealing tool to improve animal health and minimize the circulation and diversity of IAV in swine. ImportanceInfluenza A virus is an important respiratory pathogen in swine, and zoonotic transmission of swine strains to humans remains a public health risk. Control strategies against IAV in swine herds rely heavily on biosecurity measures and vaccination. However, the antigenic diversity of IAV circulating in swine challenges current vaccination programs, and there is a need for broadly protective vaccines or platforms that can rapidly update components to reflect circulating diversity. mRNA-LNP vaccines have emerged as promising vaccine platforms, offering simultaneous delivery of multiple antigens, rapid development, scalable manufacturing, and potent immunogenicity. In this study, we assessed the immunogenicity and protective capacity of monovalent and multivalent mRNA-LNP vaccines encoding eight representative IAV HA antigens. To our knowledge, this is the first study to objectively select multiple representative endemic swine IAV strains by quantifying genetic diversity within the phylogeny and to apply this selection to rationally design and evaluate a multivalent HA mRNA-based influenza vaccine in the swine model.

microbiology↗

bioRxiv2026

Evaluation of an H5 influenza virus mRNA-lipid nanoparticle (LNP) vaccine in lactating dairy cows

Highly pathogenic avian influenza (HPAI) clade 2.3.4.4b H5N1 virus has recently emerged in dairy cattle in the United States. The virus replicates primarily in the mammary gland of infected cattle, leading to dramatic reductions in milk production. It is thought that the virus transmits from animal to animal through viral shedding in milk, and therefore, vaccines that decrease the amount of virus in milk can potentially limit the current outbreak and reduce the risk of H5N1 spillover into humans. Here, we assess the immunogenicity and efficacy of a clade 2.3.4.4b H5 mRNA-LNP vaccine in lactating dairy cows. We found that the H5 mRNA-LNP vaccine elicited robust antibody responses in sera and milk and significantly reduced viral replication and disease caused by clade 2.3.4.4b H5N1 intramammary infection.

microbiology↗

bioRxiv2025

Vaccine-induced antigenic drift of a human-origin H3N2 Influenza A virus in swine alters glycan binding and sialic acid avidity

Interspecies transmission of human influenza A viruses (FLUAV) to swine occurs frequently, yet the molecular factors driving adaptation remain poorly understood. Here we investigated how vaccine-induced immunity shapes the evolution of a human-origin H3N2 virus in pigs using an in vivo sustained transmission model. Pigs (seeders) were vaccinated with a commercial inactivated swine vaccine and then infected with an antigenically distinct FLUAV containing human-origin HA/NA. Contact pigs were introduced two days later. After 3 days, seeder pigs were removed, and new contacts introduced. This was repeated for a total of 4 contacts. Sequencing of nasal swab samples showed the emergence of mutations clustered near the HA receptor binding site, enabling immune escape and abolishing binding to N-glycolylneuraminic acid. Mutant viruses recognized 2,6-sialosides with 3 N-acetyllactosamine repeats, which are rare in swine lungs, while the parental virus bound structures with a minimum of 2 repeats. Adaptative HA mutations enhanced avidity for 2,6-linked sialic acid, likely compensating for the low abundance of extended glycans. Notably, residues outside the canonical HA binding pocket contribute to glycan binding, suggesting a trade-off between receptor breadth and avidity. These findings show that non-neutralizing immunity promotes viral adaptation by fine-tuning receptor engagement and immune evasion. SIGNIFICANCEUnderstanding how vaccination shapes influenza A virus (FLUAV) evolution across species barriers is critical for predicting and preventing zoonotic and reverse-zoonotic events. Our study demonstrates that vaccine-induced immune pressure can drive antigenic drift in a human-origin H3N2 virus, altering HA receptor binding properties that could inadvertently facilitate adaptation to swine. These changes shifted glycan specificity toward extended poly-LacNAc structures and enhanced 2,6-linked sialoglycans binding while abolishing Neu5Gc recognition. By revealing how non-neutralizing immunity fine-tunes HA-glycan interactions by engaging antigenically relevant residues in glycan binding, this work highlights vaccination as an underappreciated driver of host adaptation and viral evolution.

microbiology↗

bioRxiv2025

Impact of Maternal Antibodies and Weaning Stress on the Replication and Transmission of Human H3N2 Influenza A in Piglets

Modern swine production facilitates indoor respiratory contact between human employees and pigs in their care, creating conditions for interspecies transmission of influenza A virus (IAV). Sow vaccination is routinely practiced in the U.S. to transfer maternal derived antibodies (MDA) to piglets. Weaning is a highly stressful period for piglets that requires increased human interaction. This study investigates the effect of maternal antibodies on the susceptibility of weaned piglets to a human-origin H3N2 IAV. Weaned piglets often possess mixed immunity from MDA, which may be antigenically matched or mismatched to circulating viruses. Given the repeated spillover of human seasonal H3N2 into swine, we specifically examined how matched and mismatched MDA, acquired from vaccinated sows, influenced piglet susceptibility. Additionally, we assessed the impact of weaning-related stress on the outcome of viral challenge. The H3N2 virus was generated by reverse genetics to mimic the 2010.1 H3N2 introduction from humans to swine. Challenged seeder piglets were divided by immune and weaning status. Two days post inoculation, naive direct contact pigs were placed with seeders. IAV qRT-PCR and virus titration were performed on nasal swabs and bronchoalveolar lavage fluid to evaluate shedding and transmission kinetics. Matched MDA were effective in reducing shedding in challenged pigs and minimizing transmission to contacts. There was an increase in shedding and transmission in weaned pigs compared to littermates that remained on the sow. These results identify critical control points in production where changing practices could mitigate human-to-swine and swine-to-swine transmission to prevent establishment of novel lineages in pig populations. ImportanceDefining the factors that increase the susceptibility of pigs to infection with human influenza A viruses (IAV) is critical to understand why those viruses transmit to the new host. IAV is frequently detected in nursing pigs, where it was shown that maternal derived antibodies (MDA) may reduce clinical signs but may not prevent infection and transmission. Infected weaned piglets can then move viruses from the sow farm to offsite nurseries, where they can cause outbreaks with clinical disease as MDA wanes. Determining management practices that can be modified to reduce interspecies transmission of viruses to pigs is economically beneficial to the swine industry and could help define measures to prevent new spillover events. Reducing spillover of human IAV into pig populations also benefits public health by reducing genomic and phenotypic diversity in swine and the subsequent potential for zoonotic transmission.

immunology↗

bioRxiv2025

Afferent-specific modulation of excitatory synaptic transmission by acetylcholine and serotonin in the prelimbic cortex

Acetylcholine (ACh) and serotonin (5-hydroxytryptamine, or 5-HT) differentially regulate the excitability of pyramidal neurons in the mouse prelimbic (PL) cortex according to their long-distance projections. Here we tested for afferent- and/or target-specific modulation of glutamate release by ACh and 5-HT in two long-distance excitatory projections to the PL cortex: commissural (COM) afferents from the contralateral cortex and projections from the mediodorsal nucleus (MDN) of the thalamus. Using ex-vivo optogenetic approaches, we mapped the connectivity and neuromodulation of COM and MDN afferents in layer 5 intratelencephalic (IT) and extratelencephalic (ET) projection neurons. Dual whole-cell recordings in pairs of IT and ET neurons revealed that COM afferents target both neuron subtypes, but that MDN afferents selectively target IT neurons. Both afferents exhibited similar target-independent short-term synaptic plasticity (paired-pulse facilitation) across a range of frequencies, but were differentially modulated by ACh and 5-HT. In both control conditions and after isolating monosynaptic connections with tetrodotoxin and 4-aminopyridine, COM transmission was suppressed strongly by ACh and moderately by 5-HT, while MDN transmission was largely unaffected by either neuromodulator. Suppression o,f COM transmission by ACh or 5-HT was concentration dependent and mediated by M4 muscarinic or 5-HT1B receptors, respectively. Chemogenetic inhibition of hM4Di-expressing COM terminals mimicked the suppressive effects of ACh and 5-HT on synaptic transmission. Our results demonstrate that ACh and 5-HT preferentially regulate COM synaptic transmission, albeit to different degrees, and suggest that, through their combined pre- and postsynaptic neuromodulation, ACh and 5-HT may differentially regulate cortico-striatal-thalamic loops to influence cognition and behavior.

neuroscience↗

bioRxiv2025

Sources and sinks of influenza A virus genomic diversity in swine from 2009 to 2022 in the United States

Influenza A virus (IAV) in swine in the U.S. is surveilled to monitor genetic evolution to inform intervention efforts and aid pandemic preparedness. We describe data from the U.S. Department of Agriculture National Surveillance Plan for Influenza A Virus in Pigs from 2009 to 2022. Clinical respiratory cases were subtyped followed by sequencing of hemagglutinin (HA) and neuraminidase (NA), and a subset of viruses were whole genome sequenced. Phylogenetic analysis identified geographic and temporal IAV reassortment hotspots. Regions acting as IAV genomic diversity sources or sinks were quantified, and dissemination was qualified and modeled. The dominant IAV clades were H1N2 (1B.2.1), H3N2 (1990.4.a), and H1N1 (H1-1A.3.3.3-c3). Internal genes were classified as triple-reassortant (T) or pandemic 2009 (P), and three genome constellations represented 73.5% of detections across the last two years. In some years, the distribution of IAV diversity was so narrowly distributed that it presented a statistical signal associated with local adaptation. We also demonstrated that the source of most IAV genomic diversity was in Midwest states (IL, MO, IA), and while this was correlated with swine inventory, the emergence and persistence of diversity was tied to swine transport across the U.S. The continued regional detection of unique HA, NA, and genome constellations provides support for targeted interventions to improve animal health and enhance pandemic preparedness. ImportanceVariation in the genetic diversity of influenza A virus (IAV) in swine through time and between regions impacts control efforts. This study quantified the genomic diversity of swine IAV collected from 2009-2022 at regional and national levels and modeled sources and sinks of that diversity. Seasonal patterns of IAV transmission were observed, and some locations contributed disproportionately to the emergence of genomic diversity. Minor groups of viruses had the potential to disseminate across the U.S. with animal movement. The identification of these patterns demonstrates the importance of a robust surveillance system to inform vaccine updates that reflect regional patterns of genetic diversity. We show how preemptive interventions in swine IAV diversity hubs could reduce reassortment and the emergence of novel genomic diversity, and how these efforts are likely to reduce the transmission of swine IAV within swine and between swine and humans.

microbiology↗

bioRxiv2024

Revealing reassortment in influenza A viruses with TreeSort

Reassortment among influenza A viruses (IAV) facilitates genomic evolution and has been associated with interspecies transmission and pandemics. We introduce a novel tool called TreeSort that accurately identifies recent and ancestral reassortment events on datasets with thousands of IAV whole genomes. The algorithm has immediate relevance to modern large-scale surveillance studies that generate thousands of whole genomes. TreeSort uses the phylogeny of a selected IAV segment as a reference and finds the branches on the phylogeny where reassortment has occurred with high probability by incorporating information from other gene segments. The tool reports the particular gene segments that were involved in reassortment and how different they are from prior gene pairings. Using TreeSort, we studied reassortment patterns of different IAV subtypes isolated in avian, swine, and human hosts. Avian IAV demonstrated more reassortment than human and swine IAV, with the avian H7 subtype displaying the most frequent reassortment. Reassortment in the swine and human H3 subtypes was more frequent than in the swine and human H1 subtypes, respectively. The highly pathogenic avian influenza H5N1 clade 2.3.4.4b had elevated reassortment rates in the 2020-2023 period; however, the surface protein-encoding genes (HA, NA, and MP) co-evolved together with almost no reassortment among these genes. We observed similar co-evolutionary patterns with very low rates of reassortment among the surface proteins for the human H1 and H3 lineages, suggesting that strong co-evolution and preferential pairings among surface proteins are a consequence of high viral fitness. Our algorithm enables real-time tracking of IAV reassortment within and across different hosts, can be applied to determine how specific genes evolve in response to reassortment events, and can identify novel viruses for pandemic risk assessment. TreeSort is available at https://github.com/flu-crew/TreeSort.

microbiology↗

bioRxiv2024

Experimental reproduction of viral replication and disease in dairy calves and lactating cows inoculated with highly pathogenic avian influenza H5N1 clade 2.3.4.4b

Highly pathogenic avian influenza (HPAI) H5N1 of the hemagglutinin clade 2.3.4.4b was detected in the United States in late 2021 and continues to circulate in all four North American flyways to date. In addition to impacting poultry, these HPAI viruses caused mortality events in wild bird species and wild mammals. Transmission in multiple host species raises the concern for mammalian adaptation. On March 25, 2024, HPAI H5N1 clade 2.3.4.4b was confirmed in a dairy cow in Texas in response to a multi-state investigation into milk production losses. Over one hundred positive herds were rapidly identified in Texas and eleven other U.S. states. The case description included reduced feed intake and rumen motility in lactating cows, decreased milk production, and thick yellow milk. The diagnostic investigation revealed detections of viral RNA in milk and mammary tissue with alveolar epithelial degeneration and necrosis, and positive immunoreactivity of glandular epithelium by immunohistochemistry. A single transmission event, likely from avian species to dairy cattle, followed by limited local transmission preceded the onward lateral transmission of H5N1 clade 2.3.4.4b genotype B3.13. We sought to experimentally reproduce infection with genotype B3.13 in Holstein yearling heifers and lactating cows. The heifers were inoculated by an aerosol respiratory route and the cows by an intramammary route. Clinical disease was mild in the heifers, but infection was confirmed by virus detection, lesions, and seroconversion. Clinical disease in lactating cows included decreased rumen motility, changes to milk appearance, and production losses consistent with field reports of viral mastitis. Infection was confirmed by high levels of viral RNA detected in milk, virus isolation, lesions in mammary tissue, and seroconversion. This study provides the foundation to investigate additional routes of infection, transmission, and intervention strategies.

microbiology↗

bioRxiv2024

Active surveillance for influenza A virus in swine reveals within-farm reassortment and cocirculation of distinct subtypes and genetic clades

Influenza A virus (IAV) is one of the three most frequently detected respiratory pathogens in swine. A passive IAV in swine surveillance system in the United States (U.S.) provides aggregated national metrics to quantify spatial and temporal changes in genetic diversity. However, swine production is not homogenous: production systems vary in size and management strategies that affect the transmission and evolution of IAV. To assess the impact of fine-scale variation in swine production on IAV transmission, we conducted active surveillance on sow farms and linked nurseries from 4 U.S. production systems for up to 14 monthly collections. From IAV-positive samples, we obtained 85 complete HA sequences, and of these, we successfully assembled 62 whole genomes with associated epidemiological information. To infer transmission and evolution, we conducted Bayesian phylodynamic analyses and detected six genetic clades from four HA lineages: the H1 1A classical swine, the H1 1B human-seasonal, and the H3 2010.1 and 1990.4 lineages. The 1B and H3 1990.4 strains showed evidence of transmission from sow farm to nursery. In contrast, 1A and H3 2010.1 viruses were detected in nurseries without detection in a linked sow farm. We also detected seven separate human-to- swine transmission events in the H1N1 pandemic clade (1A.3.3.2) in sow and nursery sites. Our data demonstrated that nursery sites were infected with IAV that was both linked and unlinked to the sow farm. These data suggest that control efforts may be impacted by subclinical IAV transmission in the breeding herd, the mixing of sow farm sources at the nursery, regional spread of new strains, and human-to-swine transmission. Regular surveillance activities within production systems provide the ability to match vaccine components to circulating diversity, thereby minimizing the opportunity for novel reassorted viruses to emerge and impact animal health.

bioinformatics↗

bioRxiv2024

Emergence and interstate spread of highly pathogenic avian influenza A(H5N1) in dairy cattle

Highly pathogenic avian influenza (HPAI) viruses cross species barriers and have the potential to cause pandemics. In North America, HPAI A(H5N1) viruses related to the goose/Guangdong 2.3.4.4b hemagglutinin phylogenetic clade have infected wild birds, poultry, and mammals. Our genomic analysis and epidemiological investigation showed that a reassortment event in wild bird populations preceded a single wild bird-to-cattle transmission episode. The movement of asymptomatic cattle has likely played a role in the spread of HPAI within the United States dairy herd. Some molecular markers in virus populations were detected at low frequency that may lead to changes in transmission efficiency and phenotype after evolution in dairy cattle. Continued transmission of H5N1 HPAI within dairy cattle increases the risk for infection and subsequent spread of the virus to human populations.

microbiology↗

bioRxiv2023

Nucleoprotein reassortment enhanced transmissibility of H3 1990.4.a clade influenza A virus in swine

The increased detection of H3 C-IVA (1990.4.a) clade influenza A viruses (IAV) in U.S. swine in 2019 was associated with a reassortment event to acquire an H1N1pdm09 lineage nucleoprotein (pdmNP) gene, replacing a TRIG lineage NP (trigNP). We hypothesized that acquiring the pdmNP conferred a selective advantage over prior circulating H3 viruses with a trigNP. To investigate the role of the NP reassortment in transmission, we identified two contemporary 1990.4.a representative strains (NC/19 and MN/18) with different evolutionary origins of the NP gene. A reverse genetics system was used to generate wild-type (wt) strains and to swap the pdm and TRIG lineage NP genes, generating four viruses: wtNC/19-pdmNP, NC/19-trigNP, wtMN/18-trigNP, MN/18-pdmNP. Pathogenicity and transmission of the four viruses were compared in pigs. All four viruses infected 10 primary pigs and transmitted to 5 indirect contact pigs per group. Pigs infected via contact with MN/18-pdmNP shed virus two days earlier than pigs infected with wtMN/18-trigNP. The inverse did not occur for wtNC/19-pdmNP and NC/19-trigNP. These data suggest that reassortment to acquire a pdmNP gene improved transmission efficiency in the 1990.4.a, but this is likely a multigenic trait. Replacing a trigNP gene alone may not diminish the transmission of a wild-type virus sampled from the swine population. This study demonstrates how reassortment and subsequent evolutionary change of internal genes can result in more transmissible viruses that impact the detection frequency of specific HA clades. Thus, rapidly identifying novel reassortants paired with dominant HA/NA may improve prediction of strains to include in vaccines. ImportanceInfluenza A viruses (IAV) are composed of eight non-continuous gene segments that can reassort during coinfection of a host, creating new combinations. Some gene combinations may convey a selective advantage and be paired together preferentially. A reassortment event was detected in swine in the United States that involved the exchange of two lineages of nucleoprotein (NP) genes (trigNP to pdmNP) that became a predominant genotype detected in surveillance. Using a transmission study, we demonstrated that exchanging the trigNP for a pdmNP caused the virus to shed from the nose at higher levels and transmit to other pigs more rapidly. Replacing a pdmNP with a trigNP did not hinder transmission, suggesting that transmission efficiency depends on interactions between multiple genes. This demonstrates how reassortment alters IAV transmission and that reassortment events can provide an explanation for why genetically related viruses with different internal gene combinations experience rapid fluxes in detection frequency.

microbiology↗

bioRxiv2019

NMDA receptors enhance the fidelity of synaptic integration

Excitatory synaptic transmission in many neurons is mediated by two co-expressed ionotropic glutamate receptor subtypes, AMPA and NMDA receptors, that differ in their kinetics, ion-selectivity, and voltage-sensitivity. AMPA receptors have fast kinetics and are voltage-insensitive, while NMDA receptors have slower kinetics and increased conductance at depolarized membrane potentials. Here we report that the voltage-dependency and kinetics of NMDA receptors act synergistically to stabilize synaptic integration of excitatory postsynaptic potentials (EPSPs) across spatial and voltage domains. Simulations of synaptic integration in simplified and morphologically realistic dendritic trees revealed that the combined presence of AMPA and NMDA conductances reduces the variability of somatic responses to spatiotemporal patterns of excitatory synaptic input presented at different initial membrane potentials and/or in different dendritic domains. This moderating effect of the NMDA conductance on synaptic integration was robust across a wide range of AMPA-to-NMDA ratios, and results from synergistic interaction of NMDA kinetics (which reduces variability across membrane potential) and voltage-dependence (which favors stabilization across dendritic location). When combined with AMPA conductance, the NMDA conductance balances voltage- and impedance-dependent changes in synaptic driving force, and distance-dependent attenuation of synaptic potentials arriving at the axon, to increase the fidelity of synaptic integration and EPSP-spike coupling across neuron state (i.e., initial membrane potential) and dendritic location of synaptic input. Thus, synaptic NMDA receptors convey advantages for synaptic integration that are independent of, but fully compatible with, their importance for coincidence detection and synaptic plasticity. Significance StatementGlutamate is an excitatory neurotransmitter that, at many synapses, gates two coexpressed receptor subtypes (AMPA and NMDA receptors). Computational simulations reveal that the combined synaptic presence of AMPA and NMDA receptors reduces variability in synaptic integration in response to identical patterns of synaptic input delivered to different dendritic locations and/or at different initial membrane potentials. This results from synergistic interaction of the slower kinetics and voltage-dependence of NMDA receptors, which combine to enhance synaptic currents when synaptic driving forces are otherwise reduced (e.g., at depolarized membrane potentials or in distal, high-impedance dendrites). By stabilizing synaptic integration across dendritic location and initial membrane potential, NMDA receptors provide advantages independent of, but fully compatible with, their well-known contribution to synaptic plasticity.

neuroscience↗

bioRxiv2017

Mechanisms underlying serotonergic excitation of callosal projection neurons

Serotonin (5-HT) selectively excites subpopulations of pyramidal neurons in the neocortex via activation of 5-HT2A (2A) receptors coupled to Gq subtype G-protein alpha subunits. Gq-mediated excitatory responses have been attributed primarily to suppression of potassium conductances, including those mediated by KV7 potassium channels (i.e., the M-current), or activation of nonspecific cation conductances that underly calcium-dependent afterdepolarizations (ADPs). However, 2A-dependent excitation of cortical neurons has not been extensively studied, and no consensus exists regarding the underlying ionic effector(s) involved. We tested potential mechanisms of serotonergic excitation in commissural/callosal projection neurons (COM neurons) in layer 5 of the mouse medial prefrontal cortex, a subpopulation of cortical pyramidal neurons that exhibit 2A-dependent excitation in response to 5-HT. In baseline conditions, 5-HT enhanced the rate of action potential generation in COM neurons experiencing suprathreshold somatic current injection. This serotonergic excitation was occluded by activation of muscarinic acetylcholine (ACh) receptors, confirming that 5-HT acts via the same Gq-signaling cascades engaged by ACh. Like ACh, 5-HT promoted the generation of calcium-dependent ADPs following spike trains. However, calcium was not necessary for serotonergic excitation, as responses to 5-HT were enhanced (by >100%), rather than reduced, by chelation of intracellular calcium with 10 mM BAPTA. This suggests intracellular calcium negatively regulates additional ionic conductances contributing to 2A excitation. Removal of extracellular calcium had no effect when intracellular calcium signaling was intact, but suppressed 5-HT response amplitudes, by about 50% (i.e., back to normal baseline values) when BAPTA was included in patch pipettes. This suggests that 2A excitation involves activation of a nonspecific cation conductance that is both calcium-sensitive and calcium-permeable. M-current suppression was found to be a third ionic effector, as blockade of KV7 channels with XE991 (10 M) reduced serotonergic excitation by [~]50% in control conditions, and by [~]30% with intracellular BAPTA present. These findings demonstrate a role for at least three distinct ionic effectors, including KV7 channels, a calcium-sensitive and calcium-permeable nonspecific cation conductance, and the calcium-dependent ADP conductance, in mediating serotonergic excitation of COM neurons.

neuroscience↗

bioRxiv2017

Preferential cholinergic excitation of corticopontine neurons

Pyramidal neurons in layer 5 of the neocortex comprise two broad classes of projection neurons: corticofugal neurons, including corticopontine (CPn) neurons, and intratelencephalic neurons, including commissural/callosal (COM) neurons. These non-overlapping neuron subpopulations represent discrete cortical output channels contributing to perception, decision making, and behavior. CPn and COM neurons have distinct morphological and physiological characteristics, and divergent responses to modulatory transmitters such as serotonin and acetylcholine (ACh). To better understand how ACh regulates cortical output, in slices of mouse prefrontal cortex (PFC) we compared the responsivity of CPn and COM neurons to transient exposure to exogenous or endogenous ACh. In both neuron subtypes, exogenous ACh generated qualitatively similar biphasic responses in which brief hyperpolarization was followed by longer-lasting enhancement of excitability. However, cholinergic inhibition was more pronounced in COM neurons, while excitatory responses were larger and longer lasting in CPn neurons. Similarly, optically triggered release of endogenous ACh from cholinergic terminals preferentially and persistently (for ~40 s) enhanced the excitability of CPn neurons, but had little impact on COM neurons. Cholinergic excitation of CPn neurons involved at least three distinct ionic mechanisms: activation of a calcium-sensitive but calcium-permeable nonspecific cation conductance, suppression of Kv7 channels (the \"M-current\"), and activation of the calcium-dependent nonspecific cation conductance underlying afterdepolarizations. Our results demonstrate projection-specific selectivity in cholinergic signaling in the PFC, and suggest that transient release of ACh during behavior will preferentially promote corticofugal output.

neuroscience↗