Responses of neurons in the caudal medullary lateral tegmental field to visceral inputs and vestibular stimulation in vertical planes

Abstract

The dorsolateral reticular formation of the caudal medulla, or the lateral tegmental field (LTF), has been classified as the brain's "vomiting center", as well as an important region in regulating sympathetic outflow. We examined the responses of LTF neurons in cats to rotations of the body that activate vestibular receptors, as well as to stimulation of baroreceptors (through mechanical stretch of the carotid sinus) and gastrointestinal receptors (through the intragastric administration of the emetic compound copper sulfate). Approximately half of the LTF neurons exhibited graviceptive responses to vestibular stimulation, similar to primary afferents innervating otolith organs. The other half of the neurons had complex responses, including spatiotemporal convergence behavior, suggesting that they received convergent inputs from a variety of vestibular receptors. Neurons that received gastrointestinal and baroreceptor inputs had similar complex responses to vestibular stimulation; such responses are expected for neurons that contribute to the generation of motion sickness. LTF units with convergent baroreceptor and vestibular inputs may participate in producing the cardiovascular system components of motion sickness, such as the changes in skin blood flow that result in pallor. The administration of copper sulfate often modulated the gain of responses of LTF neurons to vestibular stimulation, particularly for units whose spontaneous firing rate was altered by infusion of drug (median of 459%). The present results raise the prospect that emetic signals from the gastrointestinal tract modify the processing of vestibular inputs by LTF neurons, thereby affecting the probability that vomiting will occur as a consequence of motion sickness.

Maturation of glutamatergic transmission in the vestibulo-olivary pathway impacts on the registration of head rotational signals in the brainstem of rats

“…9a), implying that these Fos-ir MV neurons must be of canal origin. Based on the classical findings of Shimazu and Precht (1966) Vestibular signals that encode head movements close to the horizontal plane are known to be processed in medullary reticular formation (Fagerson and Barmack 1995;Chan et al 1996;Lai et al 2004;Moy et al 2012). Reticulospinal neurons in this region of the reticular formation play an important role in vestibulo-collic (Bolton et al 1992;Wilson and Schor 1999) and vestibulo-forelimb reflexes (Peterson et al 1980), contributing to postural control and locomotor function (Peterson 2004).…”

Hindlimb movement modulates the activity of rostral fastigial nucleus neurons that process vestibular input

“…4). Such responses are due to convergence of vestibular inputs with different spatial and temporal characteristics, and are thus referred to as spatiotemporal convergence (STC) responses (Schor and Angelaki 1992; Moy et al 2012). STC responses have previously been reported to be common amongst rFN neurons in the decerebrate cat (Catanzaro et al 2014).…”

Integration of vestibular and gastrointestinal inputs by cerebellar fastigial nucleus neurons: multisensory influences on motion sickness

“…The University of Pittsburgh’s Institutional Animal Care and Use Committee (IACUC) prospectively approved all procedures on animals, which were conducted in accordance with the Guide for the Care and Use of Laboratory Animals (National Research Council, National Academies Press, Washington D.C., 2011). The experimental protocol used in these experiments has been validated and thoroughly described in previous manuscripts (Sugiyama et al 2011; Moy et al 2012; Suzuki et al 2012; Arshian et al 2013), and thus will only be briefly described below.…”

“…In a series of experiments, we have investigated the effects of intragastric injection of the emetic compound copper sulfate (CuSO 4 ) on the processing of vestibular signals by brainstem regions that mediate nausea and vomiting (Sugiyama et al 2011; Moy et al 2012; Suzuki et al 2012; Arshian et al 2013). The responses to whole-body rotations that activate labyrinthine receptors of neurons in some of these areas, particularly the parabrachial nucleus (Suzuki et al 2012) and the lateral tegmental field (Moy et al 2012), were profoundly altered when CuSO 4 was present in the stomach. These findings suggest that activation of visceral receptors affects motion sickness susceptibility by altering the processing of vestibular inputs in the pathways that mediate nausea and vomiting.…”

“…As in our previous studies that considered the effects of CuSO 4 administration on the processing of labyrinthine inputs (Sugiyama et al 2011; Moy et al 2012; Suzuki et al 2012; Arshian et al 2013), recordings were conducted in decerebrate cats. We focused the recordings on the rostral portion of the fastigial nucleus, which plays a primary role in spatial orientation (Buttner et al 1991; Thach et al 1992; Siebold et al 1997; Mori et al 1998; Mori et al 2004), in contrast to the caudal aspect of the fastigial nucleus whose physiological role is related to the control of eye movements (Gardner and Fuchs 1975; Buttner et al 1991; Robinson and Fuchs 2001; Brettler and Fuchs 2002; Shaikh et al 2005).…”