Excitatory effect of norepinephrine on neurons in the inferior vestibular nucleus and the underlying receptor mechanism

Abstract

The central noradrenergic system, originating mainly from the locus coeruleus in the brainstem, plays an important role in many physiological functions, including arousal and attention, learning and memory, anxiety, and nociception. However, little is known about the roles of norepinephrine (NE) in somatic motor control. Therefore, using extracellular recordings on rat brainstem slices and quantitative real-time RT-PCR, we investigate the effect and mechanisms of NE on neuronal activity in the inferior vestibular nucleus (IVN), the largest nucleus in the vestibular nuclear complex, which holds an important position in integration of information signals controlling body posture. Here, we report that NE elicits an excitatory response on IVN neurons in a concentration-dependent manner. Activation of α1 - and β2 -adrenergic receptors (ARs) induces an increase in firing rate of IVN neurons, whereas activation of α2 -ARs evokes a decrease in firing rate of IVN neurons. Therefore, the excitation induced by NE on IVN neurons is a summation of the excitatory components mediated by coactivation of α1 - and β2 -ARs and the inhibitory component induced by α2 -ARs. Accordingly, α1 -, α2 -, and β2 -AR mRNAs are expressed in the IVN. Although β1 -AR mRNAs are also detected, they are not involved in the direct electrophysiological effect of NE on IVN neurons. All these results demonstrate that NE directly regulates the activity of IVN neurons via α1 -, α2 -, and β2 -ARs and suggest that the central noradrenergic system may actively participate in IVN-mediated vestibular reflexes and postural control. © 2016 Wiley Periodicals, Inc.

The role of the locus coeruleus in the generation of pathological anxiety

“…In the normal state and in the absence of threat, the tonic LC-NE system sustains vigilance and orienting functions ( David Johnson, 2003 ). At an early, basic level, LC projections to vestibular nuclei mediate vestibulo-ocular and vestibulospinal reflexes for alerting and vigilance ( Balaban, 2002 , 2016 ; Peng et al, 2016 ). The ability of the LC to direct attention to a given cue seems unrelated to valence ( Berridge and Waterhouse, 2003 ): the LC responds to all novel stimuli and mediates general attentional orienting ( Sara and Bouret, 2012 ; Usher et al, 1999 ).…”

Nortriptyline-Induced Room Tilt Illusion

“…Originating from the locus coeruleus and nucleus subcoeruleus, noradrenergic fibers have been found to terminate in the vestibular nuclei [19]. Additionally, it has been found that norepinephrine can elicit an excitatory response in a concentrationdependent manner on inferior vestibular nucleus neurons [20]. The inferior vestibular nucleus, as the largest nucleus of the vestibular nuclear complex within the brainstem, receives input from the vestibular nerve, carrying information from the saccule and posterior semicircular canal [21].…”

Modulatory Effects of Monoamines and Perineuronal Nets on Output of Cerebellar Purkinje Cells

“…They indicated that NA modifies GABA responses through the activation of likely postsynaptic α 2 - and/or β-adrenoceptors ( Table 1 ). In the inferior vestibular nucleus, NA directly regulates the excitability of neurons by the activation of α 1 -, α 2 - and β 2 -adrenoceptors ( Peng et al, 2016 ). In any case, NA-mediated alteration of neuronal activity in each of these nuclei would have functional significances.…”