Transforming synaptic input into action potential output is a fundamental function of neurons. The pattern of action potential output from principal cells of the mammalian hippocampus encodes spatial and nonspatial information, but the cellular and circuit mechanisms by which neurons transform their synaptic input into a given output are unknown. Using a combination of optical activation and cell type-specific pharmacogenetic silencing in vitro, we found that dendritic inhibition is the primary regulator of input-output transformations in mouse hippocampal CA1 pyramidal cells, and acts by gating the dendritic electrogenesis driving burst spiking. Dendrite-targeting interneurons are themselves modulated by interneurons targeting pyramidal cell somata, providing a synaptic substrate for tuning pyramidal cell output through interactions in the local inhibitory network. These results provide evidence for a division of labor in cortical circuits, where distinct computational functions are implemented by subtypes of local inhibitory neurons.

Ionic flux in defined cell populations mediates essential physiological and behavioral functions. Cell type-specific activators of diverse ionic conductances are needed for probing these relationships. We combined chemistry and protein engineering to enable systematic creation of a toolbox of ligand-gated ion channels (LGICs) with orthogonal pharmacologic selectivity and divergent functional properties. The LGICs and their small molecule effectors can activate a range of ionic conductances in genetically-specified cell types.LGICs constructed for neuronal perturbation can be used to selectively manipulate neuron activity in mammalian brains in vivo.The diversity of ion channel tools accessible from this approach will be useful for examining the relationship between neuronal activity and animal behavior, as well as for cell biological and physiological applications requiring chemical control of ion conductance.Ion channels are complex molecular machines with critical cell biological functions. Ligandgated ion channels (LGICs) provide rapid, remote control over conductances for different ions. In neurons, LGICs can be exploited for stimulation or silencing to examine causal relationships between electrical activity and animal behavior. Several neuron manipulation tools have been derived fromLGICs and G-protein coupled receptors (1-4) that can be genetically targeted and are reported to be orthogonal to endogenous systems. These tools are useful (5-7) but also face limitations such as ligand instability and lack of brain access (2), slow pharmacokinetics (6), the need to knockout endogenous alleles (3), or reliance on complex intracellular signaling pathways (4). Optogenetic tools (8-10) activate conductances with millisecond precision, but optimization of ion conductance properties has been limited and light targeting is invasive.To overcome these limitations, we have developed a strategy to create chimeric LGICs with distinct conductance properties derived from modular combinations of pharmacologicallyselective ligand binding domains (LBDs) and functionally diverse ion pore domains (IPDs). Within the Cys-loop receptor superfamily, the LBD of the α7 nicotinic acetylcholine receptor (nAChR) behaves as an independent actuator module that can be transplanted onto the IPDs of other Cys-loop receptors (11,12). These include at least 43 ion channel subunits in vertebrates (13), and many additional invertebrate (14) and prokaryotic (15) subunits. Distinct IPDs confer selectivity for chloride or calcium as well as nonspecific cations. For example, splicing the α7 nAChR LBD to the IPDs of the serotonin receptor 3a or the glycine receptor produces chimeric channels (α7-5HT3 or α7-GlyR) with α7 nAChR pharmacology and cation or chloride conductance properties, respectively (11,12). This modular property is a strong foundation for tailoring functional characteristics. However, the † To whom correspondence should be addressed. sternsons@janelia.hhmi.org (S.M.S.), HHMI Author ManuscriptHHMI Author Manuscript HHMI Auth...

Improved agonists for chemogenetics Targeting ligand-responsive receptors to specific groups of cells, a strategy known as chemogenetics, is a powerful tool in many neurological applications. There is increasing interest in extending these tools for human treatment. Magnus et al. designed chemogenetic ion channels that improve currently available systems and are activated by the clinically used antismoking drug varenicline. They engineered a ligand-binding domain less responsive to endogenous signals and identified agonists that function at nanomolar concentrations. The combination of drug and introduced channels transiently silenced neurons, with slow but effective washout, and induced behavioral changes in animal models after brain administration. Science , this issue p. eaav5282

Worldwide, there are nearly 10 million new cases of dementia annually, of which Alzheimer’s disease (AD) is the most common. New measures are needed to improve the diagnosis of individuals with cognitive impairment due to various etiologies. Here, we report a deep learning framework that accomplishes multiple diagnostic steps in successive fashion to identify persons with normal cognition (NC), mild cognitive impairment (MCI), AD, and non-AD dementias (nADD). We demonstrate a range of models capable of accepting flexible combinations of routinely collected clinical information, including demographics, medical history, neuropsychological testing, neuroimaging, and functional assessments. We then show that these frameworks compare favorably with the diagnostic accuracy of practicing neurologists and neuroradiologists. Lastly, we apply interpretability methods in computer vision to show that disease-specific patterns detected by our models track distinct patterns of degenerative changes throughout the brain and correspond closely with the presence of neuropathological lesions on autopsy. Our work demonstrates methodologies for validating computational predictions with established standards of medical diagnosis.

During embryonic development the myocardium enlarges by the proliferation of cardiac myocytes. Shortly after birth, cardiac myocytes lose their capacity for mitogenesis, and further growth of the myocardium to meet the increasing hemodynamic demand of an elevated blood pressure and blood volume occurs by enlargement of existing muscle cells (hypertrophy). Similarly, the restoration of myocardial contractile performance lost to ischemia or viral infection is dependent on the recovery of injured myocytes and on the compensatory enlargement of agonist myocytes. Thus, an understanding of the controlling factors of myocardial protein synthesis and growth has implications for cardiac ontogeny, adaptation to chronic physiologic and pathophysiologic stimuli, and recovery from injury.Cardiac hypertrophy is produced by a variety of stimuli in culture and in vivo (1), including, but not limited to, mechanical stretch (2, 3), neurotransmitters (4, 5), and hormones (6, 7). As the biochemistry of myocardial growth is experimentally revealed, some common intracellular signaling pathways appear among primary stimuli. For example, stretch-induced cardiomyocyte hypertrophy is mediated, in part, by the local production of angiotensin II (8), and several hypertrophic stimuli, angiotensin II, norepinephrine, and endothelin-1, act through G q protein-coupled receptors (9 -11) and activate mitogen-activated protein kinases (12, 13). Direct evidence of G q involvement in cardiac growth was provided by microinjection of G q neutralizing antibodies to block the hypertrophic response of neonatal rat ventricular myocytes to the ␣ 1 -adrenergic agonist phenylephrine (9). Thus cardiac hypertrophy appears to be mediated, at least for several stimuli, by agonists of G q proteincoupled receptors.In addition to promoting myocardial growth, angiotensin II, norepinephrine, and endothelin-1 are vasoactive substances. Interestingly, Katz (14) speculated that angiotensin II evolved from a primitive growth factor and assumed additional regulatory roles in the cardiovascular system, such as stimulation of aldosterone production and smooth muscle contraction. It is conceivable that other vasoactive substances went through a similar evolutionary process, especially in consideration of the finding that Ca 2ϩ signaling is important for angiotensin II activation of mitogen-activated protein kinase in cardiac myocytes (13).Prostaglandin F 2␣ (PGF 2␣ ) 1 is a vasoactive substance that stimulates protein synthesis in skeletal and smooth muscle cells in culture (15,16). Moreover, PGF 2␣ regulates, in part, stretch-induced skeletal myoblast growth (16), and the effects of exogenous PGF 2␣ on vascular smooth muscle hypertrophy are most likely mediated by a PGF-specific receptor (15). As to the heart, PGF 2␣ was increased in the left ventricles of rabbits by acute pressure overload (17), and PG synthase inhibitors blocked cardiac growth induced by hypertension (18) and clenbuterol (19). These observations and others suggested that PGF 2␣ may play a role in the con...

Alimentary phosphorus deprivation due to a low-phosphorus diet (LPD) elicits a profound antiphosphaturia and an increase in sodium-dependent inorganic phosphate (Pi) uptake by renal cortical brush border membrane (BBM) vesicles. But, in alimentary phosphorus deprivation due to total fasting, high urinary excretion of Pi persists. In the present study, we determined whether low tubular reabsorption of Pi in fasting is due to a diminished capacity of the specific Pi transport system with the renal cortical luminal BBM or whether it is due to a reduced transepithelial reabsorption of Pi because of metabolic conditions occurring in proximal tubule cells during fasting. Sodium-dependent Pi transport in compared with fasted rats or rats fed a normal phosphorus diet. Sodium-dependent uptake of D-glucose was significantly lower in LPD rats, compared with fast animals or animals fed a normal diet. Thus, in contrast to LPD, fasting does nt elicit an increase in Pi transport and a decrease in D-glucose transport across the isolated renal BBM. The same differences in BBM transport of Pi were present also in thyroparathyroidectomized rats. Further experiments demonstrated that the adaptation of renal function and the renal BBM transport to LPD are overridden by a subsequent period of total fasting. Results of the present study show that fasting both prevents and reverses the renal response of rats to alimentary phosphorus deprivation. The differences in Pi excretion between fasted rats, LPD rats, and LPD rats subsequently fasted are attributed, at least in part, to specific adaptive changes in sodium-dependent Pi transport across the luminal BBM, rather than to alterations in other cellular (metabolic) components of transepithelial Pi reabsorption in the proximal tubule.

Objective: To determine the utility of instillation negative pressure wound therapy (NPWT) in achieving eradication of infection and definitive wound closure in patients with infected left ventricular assist device (LVAD). Approach: A retrospective review was performed in a series of patients with infected and exposed LVADs who were treated with instillation NPWT in conjunction with surgical debridement. Results: Three consecutive patients were included who developed periprosthetic infection subsequent to LVAD implantation. In all cases, the utilization of a vacuum-assisted closure with instillation (VACi) along with surgical debridement and IV antibiotics eradicated infection resulting in successful retention of hardware. Cases 1 and 2 received definitive wound closure within 3 and 12 days of starting treatment, respectively. Case 3 initially deferred surgery in favor of local wound care. Eventually the patient elected for surgical treatment and underwent closure 164 days after initial presentation. All three patients healed completely without residual evidence of infection. Flap reconstruction with a pedicled rectus flap was used to achieve definitive closure in all patients. One patient subsequently required pump replacement secondary to thrombosis and mechanical pump failure. Innovation: LVAD infections are met with high morbidity and mortality rates, and timely salvage is critical. In this initial series, VACi has proven a viable therapy option to help control and eradicate infection without LVAD removal. Conclusion: This series illustrates the value of newer techniques such as VACi in combination with surgical debridement and antibiotic therapy in effectively salvaging LVADs that were infected.

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