The horizontal brain slice preparation: a novel approach for visualizing and recording from all layers of the tadpole tectum

Abstract

Hamodi AS, Pratt KG. The horizontal brain slice preparation: a novel approach for visualizing and recording from all layers of the tadpole tectum.

A population of gap junction-coupled neurons drives recurrent network activity in a developing visual circuit

“…Using the horizontal brain slice preparation (Hamodi and Pratt 2015), we identified an electrophysiologically distinct subpopulation of neurons located in the outermost superficial layer, along the edge of the neuropil (Fig. 1A).…”

“…Developmental stage 47-48 tadpoles (ϳ8 -12 days postfertilization) were used for all experiments. For experiments that involve recording from both superficial-layer and deep layer neurons, the horizontal brain slice preparation was performed as described by Hamodi and Pratt (2015). Briefly, tadpoles were anesthetized with 0.01% MS-222 Steinberg's solution and pinned to a block of Sylgard silicone elastomer submerged with external recording solution (in mM: 115 NaCl, 2 KCl, 3 CaCl 2 , 3 MgCl 2 , 5 HEPES, and 10 glucose, pH 7.25, osmolarity 255 mosmol/kgH 2 O) in the recording dish.…”

“…The brain was then pinned to a piece of submerged Sylgard, sliced side facing up. This horizontal brain slice preparation was previously developed specifically for accessing and recording from neurons in the outer somatic layers of the tectum, and its applications in this context have been characterized in detail (Hamodi and Pratt 2015). For experiments in which only deep layer neurons were recorded, a whole brain preparation was used as described by Pratt and Aizenman (2007) and Wu et al (1996).…”

“…To study spiking, neurons were recorded in current-clamp mode and, from a baseline of Ϫ60 mV, were injected with a 250-ms square pulse of current of varying magnitudes, and the resulting action potentials were counted. To be counted as an action potential, the height of a given action potential spike had to be at least one-half the height of the preceding spike and the width at one-half its maximal height no more than three times the width of the first action potential spike in the train (Hamodi and Pratt 2015).…”

“…In this study, we use a recently developed horizontal brain slice preparation that allows visualization and whole cell recording from all layers of the tectum (Hamodi and Pratt 2015). Taking this approach, we identified a distinct population of excitatory and gap junctionally coupled neurons residing within the superficial cell body layers of the tectum.…”