Membrane properties of excitatory and inhibitory neurons in the rat prepositus hypoglossi nucleus

Abstract

The prepositus hypoglossi nucleus (PHN) is thought to be a neural structure involved in transforming eye or head velocity signals into eye position signals for horizontal eye movements. In this study, we investigated the relationship between electrophysiological membrane properties and expression patterns of cellular markers for excitatory and inhibitory neurons by whole-cell patch clamp recordings followed by reverse transcription polymerase chain reaction (RT-PCR) analysis in rat brainstem slices. Three types of voltage response properties, namely afterhyperpolarization (AHP), firing pattern, and response to hyperpolarizing current pulses, were characterized in each neuron. Following RT-PCR analysis, we identified PHN neurons as either glutamatergic (n = 22) or GABAergic (n = 43), although a small number of cholinergic (n = 2) and glycinergic neurons (n = 1) were also identified. Both glutamatergic and GABAergic neurons showed a wide variety of membrane properties; however, we found several characteristic relationships between neuronal type and membrane properties. Most neurons exhibiting (i) AHP without a slow component, (ii) a firing pattern with a delay in the generation of the first spike, (iii) a firing pattern with a transient burst and (iv) a firing pattern with a prolonged initial interspike interval were GABAergic. On the other hand, glutamatergic neurons were primarily characterized by a low firing rate. These results indicate that there is a close relationship between specific electrophysiological membrane properties and expression of chemical markers in some types of glutamatergic and GABAergic PHN neurons.

Nicotinic acetylcholine receptor-mediated responses in medial vestibular and prepositus hypoglossi nuclei neurons showing distinct neurotransmitter phenotypes

“…The procedures for slice preparation and whole cell patch-clamp recordings were similar to those previously described (Saito and Yanagawa 2013;Shino et al 2008Shino et al , 2011Takazawa et al 2004;Zhang et al 2014). Briefly, transgenic rats (16 -21 postnatal days old; both sexes) were deeply anesthetized with isoflurane and decapitated.…”

Diverse Precerebellar Neurons Share Similar Intrinsic Excitability

“…The intrinsic excitability of neurons identified by neurotransmitter expression, synaptic input, and/or projection pattern have been examined extensively in the dorsal brainstem (Sekirnjak et al, 2003; Takazawa et al, 2004; Sekirnjak and du Lac, 2006; Bagnall et al, 2007; Shino et al, 2008; Kolkman et al, 2011; Shin et al, 2011). Despite similarities in the ability to fire in a sustained, linear fashion, firing properties of glutamatergic neurons that do not project to the cerebellum are quantitatively different from neighboring precerebellar neurons.…”

Intrinsic physiology of identified neurons in the prepositus hypoglossi and medial vestibular nuclei

“…The top row of action potentials illustrates examples of action potentials that exhibit a biphasic AHP, in which the rapid AHP was followed a slight depolarization and subsequently by second, slower AHP. These neurons would be classified as type B [7] or as AHPs+ [50]. Neurons with a similar action potential profile that play an important role in eye fixation have been observed in the NPH [32].…”

“…In contrast, many GIN and GlyT2 neurons exhibited a monophasic AHP, as illustrated in the lower panel of Fig. 3A, and would be classified as type A [7] or AHPs-[50]. …”

“…NPH neurons expressing GABAergic markers tended to differ from those expressing glutamatergic markers, but as in the MVN, considerable overlap was found between these two distinct cell types [50]. Although an extensive glycinergic projection from the NPH to the abducens nucleus has been documented [53], relatively few glycinergic neurons were identified in NPH recordings [50]. Do glycinergic neurons comprise a physiologically unique subset of NPH neurons?…”