Evidence for aspartate-immunoreactive neurons in the neostriatum of the rat: modulation by the mesencephalic dopamine pathway via D1-subtype of receptor.
Aspartate-like immunoreactivity was visualized in the neostriatum of rats using indirect immunofluorescence techniques and antibodies raised against aspartate conjugated to keyhole limpet hemocyanine. In normal rats only a few aspartate-positive cell bodies with limited processes were observed. A moderate increase was seen after treatment with (+)methamphetamine and haloperidol. A dramatic increase in the number and fluorescence intensity was observed in the unilaterally 6-hydroxy-dopamine lesioned rats after multiple injections of the D1-dopamine receptor agonist SKF 38393. In these rats strongly fluorescent processes as well as extensive terminal varicose fibre networks were observed. This increase could partly be blocked by the D1-dopamine receptor antagonist SCH 23390. Using a modified technique the aspartate-positive cell bodies and processes were observed even when the antiserum was diluted 1:80,000. Positive cell bodies and fibres were also seen on the ipsilateral side outside the neostriatum, for example in the islet of Calleja and in the piriform cortex. The aspartate-positive cells were negative for dopamine- and cyclic AMP-regulated phosphoprotein-32, a marker for neurons bearing dopamine D1-receptor subtype. A proportion of the aspartate-positive neurons (20%) contained neuropeptide tyrosine-like immunoreactivity. On adjacent sections there was a marked up-regulation of preprodynorphin-like immunoreactivity. The up-regulation of dynorphin and aspartate was only observed when there was an almost complete denervation of the neostriatum as visualized with antiserum to tyrosine hydroxylase, a marker for dopamine fibres. The present results raise the possibility that aspartate may act as a neurotransmitter released from interneurons in the neostriatum.
Pettersson
E
E
Department of Neuroscience, Karolinska Institute, Stockholm, Sweden.
Herrera-Marschitz
M
M
Rodriguez-Puertas
R
R
Xu
Z Q
ZQ
You
Z B
ZB
Hughes
J
J
Elde
R P
RP
Ungerstedt
U
U
Hökfelt
T
T
D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008636:Mesencephalon / Q000378:metabolism*; D017072:Neostriatum / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011954:Receptors, Dopamine / Q000378:metabolism*
D011954:Receptors, Dopamine; D001224:Aspartic Acid