Biology subjects

Bargmann, C.

Publications and source records attributed to Bargmann, C..

3 recordsLinked to original sources

bioRxiv2018

The C. elegans AWA Olfactory Neuron Fires Calcium-Mediated All-or-None Action Potentials

We find, unexpectedly, that C. elegans neurons can encode information through regenerative all-or-none action potentials. In a survey of current-voltage relationships in C. elegans neurons, we discovered that AWA olfactory neurons generate membrane potential spikes with defining characteristics of action potentials. Ion substitution experiments, pharmacology, and mutant analysis identified a voltage-gated CaV1 calcium channel and a Shaker-type potassium channel that underlie action potential dynamics in AWA. Simultaneous patch-clamp recording and calcium imaging in AWA revealed spike-associated calcium signals that were also observed after odor stimulation of intact animals, suggesting that natural odor stimuli induce AWA action potentials. The stimulus regimes that elicited action potentials match AWAs proposed specialized function in climbing odor gradients. Our results provide evidence that C. elegans can use digital as well as analog coding schemes, expand the computational repertoire of its nervous system, and inform future modeling of its neural coding and network dynamics.

neuroscience↗

bioRxiv2018

Parallel multimodal circuits control an innate foraging behavior

Foraging strategies that enable animals to locate food efficiently are composed of highly conserved behavioral states with characteristic features. Here, we identify parallel multimodal circuit modules that control an innate foraging state -- local search behavior -- after food removal in the nematode Caenorhabditis elegans. Two parallel groups of chemosensory and mechanosensory glutamatergic neurons that detect food-related cues trigger local search by inhibiting separate integrating neurons through a metabotropic glutamate receptor, MGL-1. The chemosensory and mechanosensory modules are separate and redundant, as glutamate release from either can drive the full behavior. Spontaneous activity in the chemosensory module encodes information about the time since the last food encounter and correlates with the foraging behavior. In addition, the ability of the sensory modules to control local search is gated by the internal nutritional state of the animal. This multimodal circuit configuration provides robust control of an innate adaptive behavior.

neuroscience↗

bioRxiv2017

Diverse modes of synaptic signaling, regulation, and plasticity distinguish two classes of C. elegans glutamatergic neurons

Synaptic vesicle release properties vary between neuronal cell types, but in most cases the molecular basis of this heterogeneity is unknown. Here, we compare in vivo synaptic properties of two neuronal classes in the C. elegans central nervous system, using VGLUT-pHluorin to monitor synaptic vesicle exocytosis and retrieval in intact animals. We show that the glutamatergic sensory neurons AWCON and ASH have distinct synaptic dynamics associated with tonic and phasic synaptic properties, respectively. Exocytosis in ASH and AWCON is differentially affected by SNARE-complex regulators that are present in both neurons: phasic ASH release is strongly dependent on UNC-13, whereas tonic AWCON release relies upon UNC-18 and on the protein kinase C homolog PKC-1. Exocytosis and retrieval each have two timescales in AWCON but one major timescale in ASH. Strong stimuli that elicit high calcium levels also increase exocytosis and retrieval rates in AWCON, generating distinct tonic and evoked synaptic modes. These results highlight the differential deployment of shared presynaptic proteins in neuronal cell type-specific functions.

neuroscience↗