In vivo characterization of somatodendritic dopamine release in the substantia nigra of 6-hydroxydopamine-lesioned rats
Article first published online: 17 MAY 2004
Journal of Neurochemistry
Volume 90, Issue 1, pages 29–39, July 2004
How to Cite
Sarre, S., Yuan, H., Jonkers, N., Van Hemelrijck, A., Ebinger, G. and Michotte, Y. (2004), In vivo characterization of somatodendritic dopamine release in the substantia nigra of 6-hydroxydopamine-lesioned rats. Journal of Neurochemistry, 90: 29–39. doi: 10.1111/j.1471-4159.2004.02471.x
- Issue published online: 17 MAY 2004
- Article first published online: 17 MAY 2004
- Received September 22, 2003; revised manuscript received January 15, 2004; accepted February 10, 2004.
- Parkinson's disease;
- substantia nigra;
- tyrosine hydroxylase immunostaining
We investigated the effect of an injection of 6-hydroxydopamine (6-OHDA) into the rat medial forebrain bundle (MFB) on the degeneration and the function of the dopaminergic cell bodies in the substantia nigra (SN) 3 and 5 weeks after lesioning. After injection of 6-OHDA into the MFB a complete loss of dopamine content was apparent in the striatum 3 weeks after lesioning. In the SN the amount of tyrosine hydroxylase-immunoreactive dopamine cells decreased gradually, with a near-complete lesion (> 90%) obtained only after 5 weeks, indicating that neurodegeneration of the nigral cells was still ongoing when total dopamine denervation of the striatum had already been achieved. Baseline dialysate and extracellular dopamine levels in the SN, as determined by in vivo microdialysis, were not altered by the lesion. A combination of compensatory changes of the remaining neurones and dopamine originating from the ventral tegmental area may maintain extracellular dopamine at near-normal levels. In both intact and lesioned rats, the somatodendritic release was about 60% tetrodotoxin (TTX) dependent. Possibly two pools contribute to the basal dopamine levels in the SN: a fast sodium channel-dependent portion and a TTX-insensitive one originating from diffusion of dopamine. Amphetamine-evoked dopamine release and release after injection of the selective dopamine reuptake blocker GBR 12909 were attenuated after a near-complete denervation of the SN (5 weeks after lesioning). So, despite a 90% dopamine cell loss in the SN 5 weeks after an MFB lesion, extracellular dopamine levels in the SN are kept at near-normal levels. However, the response to a pharmacological challenge is severely disrupted.