Morphological and electrophysiological properties of a novel in vitro preparation: the electrosensory lateral line lobe brain slice

Abstract

An in vitro brain slice preparation of the electrosensory lateral line lobe (ELL) of weakly electric fish was developed. The morphology of this slice was studied and revealed that most ELL neurons and synapses retained their normal appearance for at least 10 h in vitro. The electrophysiological characteristics of the main ELL output neurons, the pyramidal cells, were measured. Extracellular electrode recordings demonstrated that pyramidal cells are capable of spontaneous, rhythmic spike activity. Intracellular recordings showed that intrinsic oscillations in membrane potential underlie the bursting behavior. The majority of pyramidal cells respond to depolarizing current pulses with an initial lag in spike firing followed by a non-accommodating, higher frequency spike train. Time and voltage-dependent properties of pyramidal cell responsiveness, as well as the effects of pharmacological blocking agents indicated that rhythmic activity and repetitive firing are dominated by a persistent, subthreshold sodium conductance (gNa) which activates at depolarizing levels and is the driving force behind the membrane potential oscillations and the sustained (non-accommodating) spike firing. In addition, a transient, outward potassium conductance (gA) is responsible for the lag in spike firing by acting as a 'brake' during the initial 50-200 ms of a depolarizing stimulus. Calcium currents and calcium-dependent potassium conductance add to the interval between spontaneous bursts but appear insufficient for spike frequency accommodation. The in vitro behaviour of pyramidal cells differs substantially from the behaviour of the same cell type in vivo. These observations raise possibilities that intrinsic membrane properties together with local synaptic interactions may regulate pyramidal cell responsiveness.

Ionic and neuromodulatory regulation of burst discharge controls frequency tuning

“…More hyperpolarized levels can remove the inactivation of I A and thereby increase first spike latency (Connor and Stevens, 1971;McCormick, 1991;Schoppa and Westbrook, 1999). A similar voltage dependence of first spike latency was shown for some ELL pyramidal neurons (Mathieson and Maler, 1988). It was found that carbachol significantly shortened the first spike latency after a step depolarization (Fig.…”

“…In ELL pyramidal neurons, a 4-AP sensitive A-type subthreshold K + current was previously shown to control the first spike latency following a step depolarization (Mathieson and Maler, 1988). The initial period before spiking is controlled by the membrane potential value preceding depolarization.…”

“…The source of cholinergic inputs to the ELL-Cholinergic input unto pyramidal cells most likely originates from eurydendroid cells within the caudal lobe of the cerebellum (Phan and Maler, 1983;Maler et al, 1981;Mathieson and Maler, 1988;Berman and Maler, 1999). The circuitry within the caudal lobe of the cerebellum is similar to that of the deep cerebellar nuclei in mammalian systems (Finger, 1978).…”

Dopaminergic Modulation of Mitral Cells and Odor Responses in the Zebrafish Olfactory Bulb

“…Experiments were performed in an explant preparation of the intact brain and nose as described previously ; an article describing the dissection procedure and the flow chamber in more detail is in preparation. Briefly, fish were decapitated under cold anesthesia, the ventral OB and telencephalon were exposed after removal of the eyes, and the preparation was placed into a custom-made flow chamber perfused with artificial CSF (ACSF) (Mathieson and Maler, 1988) at room temperature (ϳ22°C) (Friedrich and Laurent, 2001). The flow chamber was perfused at a rate of ϳ3 ml/min and had a volume of Ͻ0.5 ml, allowing for fast exchange of solutions.…”

SK Channels Provide a Novel Mechanism for the Control of Frequency Tuning in Electrosensory Neurons

“…Intracellular recordings from pyramidal neurons in an in vitro slice preparation of the ELL (Mathieson and Maler, 1988;Turner et al, 1994;Berman and Maler, 1999) were used to assess the spike responses across the ELL. Spikes were evoked through stimulation with a suprathreshold current injection.…”