Serotonin and serotonin receptors in the central auditory system

Abstract

Immunohistochemical and ligand-binding techniques were used to visualize the neurotransmitter serotonin and one of its receptors, the 5-HT1A subtype, in auditory nuclei of the brainstem. Serotonergic fibers and terminal endings were found in all auditory nuclei extending from the cochlear nucleus to the inferior colliculus, including the superior olivary complex and the nuclei of the lateral lemniscus. The density of the innervation varied between and within each nucleus. All serotonergic cell bodies were located outside the auditory nuclei. The 5-HT1A receptor subtype was found in the cochlear nucleus as well as in the inferior colliculus. With no serotonergic cell bodies present in the auditory nuclei, the present neuroanatomic and neurochemical findings support behavioral and neurophysiologic findings that the serotonergic system may modulate central auditory processing.

The serotonin releaser fenfluramine alters the auditory responses of inferior colliculus neurons

“…The number of neurons showing effects of fenfluramine that could be blocked by the antagonists was relatively small compared to the total sample size (Table 1, 1 st column), and the responses of some neurons to fenfluramine were not altered by the antagonists (Table 1, 2 nd column). This is consistent with the diversity of serotonin receptor types thought to be present in the IC (Thompson et al 1994;Peruzzi and Dut 2004;Cornea-Hébert et al 1999;Harlan et al 2000;Morales et al 1998;Vilaró et al 2005;To et al 1995;Heidmann et al 1998), because using antagonists selective for one or two receptor types would not be effective for neurons without these receptor types.…”

“…We directly tested this hypothesis in a set of 34 IC neurons by applying fenfluramine concurrently with several different serotonin (5-HT) receptor antagonists after observing the effects of fenfluramine alone. Among the 7 families of serotonin receptor, many have been reported to be present in the IC (for example, 5-HT1: Thompson et al 1994;Peruzzi andDut 2004, 5-HT2: Cornea-Hébert et al 1999;Harlan et al 2000, 5-HT3: Morales et al 1998, 5-HT4: Vilaró et al 20055-HT7: To et al 1995;Heidmann et al 1998). This means that no single type of serotonin receptor antagonist is likely to block all of the effects of fenfluramine-evoked serotonin release.…”

“…Thus, the strategy taken to evaluate whether serotonin receptor antagonists block any of the effects of fenfluramine was to use antagonists against two common types of serotonin receptor, both alone and in combination. The first of these antagonists, WAY-100635, selectively blocks the 5-HT1A receptor (Fletcher et al 1996), a receptor type that is expressed by many IC neurons (Thompson et al 1994;Peruzzi and Dut 2004). The second antagonist, mianserin, may be relatively selective for 5-HT2 receptors, but it also has affinity for 5-HT1, 5-HT6 and 5-HT7 receptors (Hoyer et al 1994).…”

Subcortical processing in auditory communication

“…These feature-specific responses in the IC are also observed at higher levels of complexity, for example in terms of overrepresentation of species-specific vocalisations (Portfors et al, 2009). Further indication that the IC plays a central role in linking sonic features of vocalisations with behaviourally relevant affective meaning comes from evidence of innervation and modulation of IC responses by serotonin (Thompson et al, 1994;Hurley and Pollak, 1999;Hurley and Thompson, 2001;Hurley et al, 2002), a neurotransmitter known for its involvement in social interaction. Combining behavioural observation (e.g.…”

Pathophysiology and Treatment of Tinnitus: An Elusive Disease

“…Serotonin and GABA receptors are found throughout the auditory system, and neurotransmitter abnormalities have been purported to play a role in some patients [25,26]. Attempts at symptomatic relief have included antidepressants (e.g.…”