CIUSSS Capitale nationale logo

Distribution and ultrastructural features of the serotonin innervation in rat and squirrel monkey subthalamic nucleus.

Publication Type:

Journal Article

Source:

Eur J Neurosci, Volume 31, Issue 7, p.1233-42 (2010)

Keywords:

Animals, Axons, Male, Microscopy, Electron, Transmission, Nerve Fibers, Neural Pathways, Neurons, Rats, Rats, Sprague-Dawley, Receptors, Serotonin, Saimiri, Species Specificity, Statistics, Nonparametric, Subthalamic Nucleus, Synapses

Abstract:

<p>The main purpose of this light and electron microscopic immunocytochemical study was to characterize and compare the serotonin (5-HT) innervation of the subthalamic nucleus (STN) in rats and squirrel monkeys (Saimiri sciureus) following labeling with an antibody against the 5-HT transporter (SERT). Unbiased counts of SERT+ axon varicosities revealed an average density of 5-HT innervation higher in monkeys (1.52 x 10(6) varicosities/mm3) than rats (1.17 x 10(6)), particularly in the anterior half of the nucleus (1.70 x 10(6)). As measured by electron microscopy, SERT+ axon varicosity profiles in the STN of both species were smaller than unlabeled profiles. The number of SERT+ profiles displaying a synaptic junction indicated that, in both rat and monkey STN, approximately half of 5-HT axon varicosities were asynaptic. In monkeys, all synaptic junctions made by SERT+ varicosities were asymmetrical, as opposed to only 77% in rats. Despite the higher density of 5-HT innervation in the anterior half of monkey STN, the ultrastructural features of its SERT+ varicosities, including synaptic incidence, did not significantly differ from those in its posterior half. These findings suggest that, throughout the rat and monkey STN, 5-HT afferents may exert their influence via both synaptic delivery and diffusion of 5-HT, and that an ambient level of 5-HT maintained in STN by these two modes of transmission might also modulate neuronal activity and influence motor behavior. A better understanding of the factors governing the complex interplay between these signaling processes would greatly improve our knowledge of the physiopathology of the STN.</p>

Funding / Support / Partners

logo FRQ-S logo ctrn logo fci logo cihr irsc logo nserc logo MESISentinelle nord