AMPA receptor mediated synaptic excitation drives state-dependent bursting in Purkinje neurons of zebrafish larvae

Abstract

Purkinje neurons are central to cerebellar function and show membrane bistability when recorded in vitro or in vivo under anesthesia. The existence of bistability in vivo in awake animals is disputed. Here, by recording intracellularly from Purkinje neurons in unanesthetized larval zebrafish (Danio rerio), we unequivocally demonstrate bistability in these neurons. Tonic firing was seen in depolarized regimes and bursting at hyperpolarized membrane potentials. In addition, Purkinje neurons could switch from one state to another spontaneously or with current injection. While GABAAR or NMDAR were not required for bursting, activation of AMPARs by climbing fibers (CFs) was sufficient to trigger bursts. Further, by recording Purkinje neuron membrane potential intracellularly, and motor neuron spikes extracellularly, we show that initiation of motor neuron spiking is correlated with increased incidence of CF EPSPs and membrane depolarization. Developmentally, bistability was observed soon after Purkinje neuron specification and persists at least until late larval stages.DOI: http://dx.doi.org/10.7554/eLife.09158.001

Distinct responses of Purkinje neurons and roles of simple spikes during associative motor learning in larval zebrafish

“…Most Purkinje cells also showed EPSPs with long-lasting depolarizations (>200 ms) that evoked simple spikes, which could outlast swimming (N = 26/39; Figure 2A, top three panels ), while others showed long-lasting hyperpolarizations of 5 to 10 mV (N = 9/39 cells; Figure 2A , bottom ). These observations are consistent with previous descriptions of spontaneous, motor-related Purkinje cell responses in larval zebrafish (Sengupta and Thirumalai, 2015).

10.7554/eLife.22537.003Figure 2.Purkinje cell responses during sensory stimuli and motor commands associated with fictive swimming.( A ) Responses of four different Purkinje cells (top to bottom) during spontaneous swimming, showing different combinations of climbing fiber, parallel fiber, and putative inhibitory input, resulting in complex spikes, simple spikes with long-lasting depolarizations, and/or hyperpolarization.

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Acid–base physiology, neurobiology and behaviour in relation to CO2-induced ocean acidification

“…For example, when neurons are in a down state, the reversal potential for Cl − can be higher than the membrane potential, so the opening of GABA A Rs can be excitatory in nature; however, in an up state, GABA A R regains its inhibitory action (Plenz, 2003). Intracellular recordings in larval zebrafish demonstrate that Purkinje neurons also fluctuate between up states, when they fire bursts of action potentials, and down states, when only short bursts of action potentials occur with AMPA receptor activation (Sengupta and Thirumalai, 2015). Taken together, a shift in E GABA would have a prominent effect when the neuron is in the down state but not in the up state.…”

Medaka and zebrafish contactin1 mutants as a model for understanding neural circuits for motor coordination

“…Electrophysiological analysis, which is feasible for studying cerebellar functions (Hsieh et al . ; Sengupta & Thirumalai ; Scalise et al . ), will show whether and how cerebellar neural circuits are affected in the mutants.…”

“…Our data suggest that small changes in synapses and other microstructures in the cerebellar neural circuits of cnt-n1b-mutant medaka and zebrafish might cause abnormalities in oculomotor response and swimming. Electrophysiological analysis, which is feasible for studying cerebellar functions (Hsieh et al 2014;Sengupta & Thirumalai 2015;Scalise et al 2016), will show whether and how cerebellar neural circuits are affected in the mutants.…”

“…Like other members of the Contactin (Cntn) family, Cntn1 (previously known as F11 in chickens and F3 in mice) is a membrane-anchored molecule with six Ig-superfamily domains, four fibronectin type III (FN) domains and a GPI (glycosyl phosphatidyl inositol) anchor (Ranscht 1988;Brummendorf et al 1989;Gennarini et al 1989;Shimoda & Watanabe 2009). In mice, Cntn1 is expressed in differentiated neurons in various regions of the CNS, including granule cells, Golgi cells and Purkinje cells in the cerebellum; pyramidal and granule neurons in the hippocampus; olfactory nerve fibers, mitral cells and synaptic glomeruli in the olfactory sensory system (Faivre-Sarrailh et al 1992;Virgintino et al 1999); in specialized domains of myelinated fibers called the nodes and paranodes of Ranvier (Peles & Salzer 2000;Girault & Peles 2002;Poliak & Peles 2003;Salzer 2003); and at neuromuscular junctions (Compton et al 2008).…”