These data have been presented in part in abstract form at the 12th Annual Meeting of the Society for Neuroscience, Minneapolis, MN, October 31-November 5, 1982.
Rapid Release of [3H]Dopamine from Median Eminence and Striatal Synaptosomes
Article first published online: 5 OCT 2006
Journal of Neurochemistry
Volume 48, Issue 4, pages 1222–1230, April 1987
How to Cite
Gregerson, K. A. and Selmanoff, M. (1987), Rapid Release of [3H]Dopamine from Median Eminence and Striatal Synaptosomes. Journal of Neurochemistry, 48: 1222–1230. doi: 10.1111/j.1471-4159.1987.tb05650.x
- Issue published online: 5 OCT 2006
- Article first published online: 5 OCT 2006
- Received July 30, 1986; revised October 15, 1986; accepted October 17, 1986
- Median eminence;
Abstract: Release of preaccumulated, tritium-labeled dopa-mine ([3H]DA) from preparations of isolated nerve terminals (synaptosomes) of rat median eminence (ME) and corpus striatum (CS) was examined over short time intervals (1–20 s). In both preparations, basal efflux of [3H]DA was linear with time. Depolarization with high K+ resulted in an initial rapid release of [3H]DA which stabilized by 20 s, whereas veratridine elicited an increased rate of release over basal levels that was linear over the first 20 s. The calculated rate constants of release for both the initial phase of K+-and the veratridine-stimulated release were approximately threefold greater in CS than in ME synaptosomes. The major component of the high K+-induced release of [3H]DA from both synaptosome preparations increased as a graded function of [Ca2+]o. However, a smaller component, independent of external Ca2+, existed in both ME and CS synaptosomes. Increasing the [Mg2+] in the external solution resulted in a right shift of both the [K+]o and the [Ca2+]o dose-response curves, consistent with actions of Mg2+ on screening surface membrane charges and blocking voltage-dependent Ca2+ channels. In all studies, steady-state uptake of the [3H]DA was about twofold greater into CS than into ME synaptosomes. Moreover, the fraction of incorporated [3H]DA released by stimulation from the CS was much greater than that released from ME synaptosomes. These data are consistent with differences between these two types of dopaminergic terminals with respect to packaging and/ or distribution of the accumulated neurotransmitter in intraneuronal pools, as well as marked differences in the apparent kinetics of DA release.