Abstract
Histaminergic afferent system of the cerebellum, having been considered as an essential component of the direct hypothalamocerebellar circuits, originates from the tuberomammillary nucleus in the hypothalamus. Unlike the mossy fibers and climbing fibers, the histaminergic afferent fibers, a third type of cerebellar afferents, extend fine varicose fibers throughout the cerebellar cortex and nuclei. Histamine receptors, belonging to the family of G protein-coupled receptors, are widely present in the cerebellum. Through these histamine receptors, histamine directly excites Purkinje cells and granule cells in the cerebellar cortex, as well as the cerebellar nuclear neurons. Therefore, the histaminergic afferents parallelly modulate these dominant components in the cerebellar circuitry and consequently influence the final output of the cerebellum. In this way, the histaminergic afferent system actively participates in the cerebellum-mediated motor balance and coordination and nonsomatic functions. Accordingly, histaminergic reagents may become potential drugs for clinical treatment of cerebellar ataxia and other cerebellar disease. On the other hand, considering the hypothalamus is a high regulatory center for autonomic and visceral activities, the hypothalamocerebellar histaminergic fibers/projections, bridging the nonsomatic center to somatic structure, may play a critical role in the somatic-nonsomatic integration.
Highlights
The cerebellum is a well-known important subcortical motor structure, ensuring coordination, precision, and accurate timing of movement, and learning motor skills [1,2,3,4]
Histamine was isolated from peripheral tissues as a biologically active amine more than a century ago, histamine acting as a neurotransmitter in the brain and the central histaminergic system gained general acceptance only in recent 30 years [14]
Different from serotoninergic and norepinephrinergic afferents arising from the brainstem [6,13], histaminergic fibers originate from the hypothalamus, a higher center for nonsomatic visceral and autonomic regulation [15,16]
Summary
The cerebellum is a well-known important subcortical motor structure, ensuring coordination, precision, and accurate timing of movement, and learning motor skills [1,2,3,4]. Cerebellar histaminergic afferent fibers originate from the tuberomammillary nucleus in the hypothalamus and project to both of the cerebellar cortex and nuclei They parallelly modulate the Purkinje cells, granule cells and nuclear neurons via H2 and/or H1 receptors and sequentially influence the outputs of the cerebellum. Due to histaminergic varicose endings and histamine metabotropic receptors, the hypothalamic histaminergic afferent system may not transmit fast signals, but act as a biasing force to influence electrophysiological properties of cerebellar and vestibular neurons and hold their excitability and sensitivity at an appropriate level for responding to inputs coding changes in internal and external environments. Experimental results are very preliminary, they provide a new insight and indicate a possibility of using histaminergic reagents to ameliorate symptoms of cerebellar ataxia
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
