Glutamate and aspartate immunoreactivities in the nucleus submedius of rats

Glutamate and aspartate immunoreactivities in the nucleus submedius of rats

Field: Sensory systems

Authors: Persson, Stefan
Broman, Jonas

Address of presenting
author: Inst för Fysiologiska Vetenskaper
Avd för Neurofysiologi
Sölvegatan 19
223 62 LUND

E-mail: Stefan.Persson@mphy.lu.se

Phone: +46 (0)46 222 77 66

Fax: +46 (0)46 222 45 46

Text of abstract: Ascending spinal and trigeminal inputs of importance for the perception of pain terminate in several different regions in both the medial and lateral thalamus. In the medial thalamus, the nucleus submedius (Sm) has been shown to receive dense inputs from both the spinal and trigeminal dorsal horns. Since neurons in Sm project to the ventrolateral orbital (VLO) cortex in both cats and rats, and neurons in both Sm and VLO respond to noxious stimulation, it has been proposed that Sm is a medial thalamic center for nociception of importance for the affective/motivational aspects of pain.
Knowledge of the nature of synaptic transmission of such signals in Sm could be used in blocking these signals before they reach higher centers, where a conscious experience of the pain is formed.
A previous study in cats has demonstrated that spino- and trigeminothalamic terminals in Sm are enriched in glutamate-like immuno reactivity, proposing a role for glutamate as a neurotransmitter of nociceptive signals in Sm.
The most abundant endogenous compound that bind and activate excitatory amino acid receptors, next to glutamate, is aspartate, which also has been found in excitatory terminals in the Hippocampus.
The aims of the present study was therefore to examine if the terminals of trigeminal afferents to Sm are enriched in glutamate in rats as they are in cats, and to examine a possible enrichment of aspartate in such terminals.
To this end an electron microscopy immunogold study of anterograde-labelled terminals of the Sm, using antiserum against glutamate and aspartate, was conducted on three rats.
While the results of the glutamate study remain inconclusive, preliminary results indicate that it is unlikely that aspartate is enriched in the excitatory terminals of the Sm in rats.

Keywords: Submedius, rat, nociception, immunogold

	Glutamate and aspartate immunoreactivities in the nucleus submedius of rats
Field:	Sensory systems
Authors:	Persson, Stefan Broman, Jonas
Address of presenting author:	Inst för Fysiologiska Vetenskaper Avd för Neurofysiologi Sölvegatan 19 223 62 LUND
E-mail:	Stefan.Persson@mphy.lu.se
Phone:	+46 (0)46 222 77 66
Fax:	+46 (0)46 222 45 46
Text of abstract:	Ascending spinal and trigeminal inputs of importance for the perception of pain terminate in several different regions in both the medial and lateral thalamus. In the medial thalamus, the nucleus submedius (Sm) has been shown to receive dense inputs from both the spinal and trigeminal dorsal horns. Since neurons in Sm project to the ventrolateral orbital (VLO) cortex in both cats and rats, and neurons in both Sm and VLO respond to noxious stimulation, it has been proposed that Sm is a medial thalamic center for nociception of importance for the affective/motivational aspects of pain. Knowledge of the nature of synaptic transmission of such signals in Sm could be used in blocking these signals before they reach higher centers, where a conscious experience of the pain is formed. A previous study in cats has demonstrated that spino- and trigeminothalamic terminals in Sm are enriched in glutamate-like immuno reactivity, proposing a role for glutamate as a neurotransmitter of nociceptive signals in Sm. The most abundant endogenous compound that bind and activate excitatory amino acid receptors, next to glutamate, is aspartate, which also has been found in excitatory terminals in the Hippocampus. The aims of the present study was therefore to examine if the terminals of trigeminal afferents to Sm are enriched in glutamate in rats as they are in cats, and to examine a possible enrichment of aspartate in such terminals. To this end an electron microscopy immunogold study of anterograde-labelled terminals of the Sm, using antiserum against glutamate and aspartate, was conducted on three rats. While the results of the glutamate study remain inconclusive, preliminary results indicate that it is unlikely that aspartate is enriched in the excitatory terminals of the Sm in rats.

Keywords:	Submedius, rat, nociception, immunogold

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Created 2000-03-15

Department of Physiological Sciences, Lund University

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