Modulatory Role of Neuropeptides in the Cerebellum

Abstract

The existence of neuropeptides in the central nervous system has been known for almost 40 years. Within the cerebellum approximately 22 neuropeptides have been identified. However, the functional role(s) for many of the different peptides in the cerebellum is largely unknown as their distribution in the cerebellum is not uniform and varies between species. Further, to date sufficient physiological analysis has not been carried out to determine the potential importance of cerebellar peptides. It has been proposed that peptides slowly modulate cerebellar circuits by acting through G protein-coupled receptors in contrast to the fast action of amino acid neurotransmitters that bind to ionotropic receptors. This effect, in turn, would influence the state of an entire neuronal circuit rather than a single neuron. This chapter will be focused on two members of the corticotropin-releasing factor (CRF) family of peptides, namely, corticotropin-releasing factor and urocortin because their distribution has been described in multiple species and their function has been investigated to a greater extent than any of the other peptides found in the cerebellum. A review of the distribution of these peptides as well as a discussion of their cognate receptors is included. Data on the functional role of both peptides is presented. It is clear that complex interactions take place between these peptides and other transmitters in the cerebellum. The physiological data suggest that CRF is essential for normal cerebellar-mediated motor performance. There is less data on the physiological role of urocortin (UCN) in the cerebellum. To date, it has been shown that UCN increases the spontaneous firing rate

Three urocortins in medaka: identification and spatial expression in the central nervous system

“…A unique feature of medaka ucn3 expression is its occurrence in the cerebellum (VC and CbSg), in which, to our knowledge, neurones expressing any CRH family members have not been identified in any species. However, substantial evidence exists to suggest that many CRH‐expressing neurones, including those in the inferior olive, project to the cerebellum, and CRH is essential for normal cerebellar‐mediated motor performance . In medaka, UCN3 expressed within the cerebellum may serve this role by acting in a paracrine and/or autocrine manner.…”