Nociceptive responses of the posterior thalamic nucleus to peripheral noxious stimuli in anesthetized rats
Date Issued
2011
Date
2011
Author(s)
Chen, Chih-Ping
Abstract
The thalamus is well known to play an important role in nociception, and several thalamic nuclei are recruited to participate in the medial and lateral pain pathways. However, the role of the posterior thalamic nucleus (Po) in nociception is controversial, which is located at the border between the medial and lateral thalamus and is as large in volume as the ventral posterolateral thalamic nucleus (VPL) or the posteromedial thalamic nucleus (VPM). Previous pain-related studies often referred to the Po as an auxiliary structure, and most of these studies assessed several sensory modalities since there are only a few nociceptive-specific (NS) responses that can be assessed. In this thesis, a range of assessment techniques will be used to explore the role of the Po in nociception, using both micro- and macro-view approaches. Features of neurons of the Po were compared to characteristics of thalamic neurons known to belong to the lateral pain pathway. Therefore, NS responses were the focus of this thesis, and the entire lateral thalamus was systematically explored. To improve the quality of the experimental findings, development of an adequate quantitative mechanical pinch stimulator was also incorporated. The results of the unit recording study by use of the pinch stimulator showed that the incidence of 9% (39 of 245 units) was found in our systematic study. Nine of the 39 NS units identified (23%) were located in the VPL, and 22 of the 39 units identified (56%) were located in the Po. Otherwise, Po was found with topographical orientation (i.g., it is not clearly organized) while focus on the tail and hind paws stimulated. And few units were identified within the posterior triangular neurons of the Po (PoT). In responses of ipsi-laterality, 14% of NS units (3 of 22 units) responded ipsilaterally. The preliminary results from CSD mapping of 2.5 mm (stand for rostral portion) and 3.8 mm (caudal portion) partly supported the results above mentioned. The results of our electrophysiological investigation into the role of the Po in nociception revealed that the Po is involved in processing nociceptive information and could play an indispensable role in either the lateral or medial pain pathway. These findings may have implication for the development of pain management strategies and translational research in other species.
Subjects
nociception
thalamus
posterior thalamic nucleus (Po)
rat
pinch
mechanical noxious pinch
CO2 laser
current source density (CSD)
Type
thesis
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