Role of cyclic AMP in dopamine modulation of potassium channels on rat striatal neurons: Regulation of a subconductance state
✍ Scribed by Gabriela J. Greif; Yong-Jian Lin; Jonathan E. Freedman
- Publisher
- John Wiley and Sons
- Year
- 1995
- Tongue
- English
- Weight
- 322 KB
- Volume
- 21
- Category
- Article
- ISSN
- 0887-4476
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✦ Synopsis
Striatum
Dz receptor, Patch-clamp, K' channel, Sp-CAMPS, Caudate-putamen,
The original classification of dopamine receptors into the D1 and Dz receptor subtypes was based in large part on the receptors' respective effects on the cyclic AMP (CAMP) second messenger system, with D, receptors positively coupled to adenylyl cyclase, and Dz receptors either negatively coupled or not coupled (Kebabian and Calne, 1979). However, the fact that a neurotransmitter receptor can regulate a second messenger does not necessarily indicate that the second messenger, in turn, mediates the effects of the receptor on membrane excitability via ion channels. We are studying a n 85-pS Kt channel that is modulated by D2-like dopamine receptors on freshly dissociated rat corpus striatum (caudateputamen) neurons (Freedman and Weight, 1988; Greif et al., 1995a,b). Here we have used patch-clamp recordings to evaluate the effects of CAMP analogs on the activation of this channel.
Rat caudate-putamen neurons were freshly dissociated, and cells with diameters 2 1 0 pm were used for cell-attached patch-clamp electrophysiology according to methods previously described (Greif et al., 1995a). Recordings were filtered a t 2 kHz low pass and digitally acquired at 100 pseclpoint. Records of 256,000 points were used for generation of all-points amplitude histograms. Dopamine was routinely applied via the patch pipette. In control experiments, this channel was never observed in 130 recordings in the absence of dopaminergic agonists (Greif et al., 1995a). In some experiments, test compounds were applied in the solution used for superfusion of the cells, by application via gravity perfusion from a macropipette of tip diameter approximately 200 pm, positioned about 500 pm above the cell. All dopamine solutions also contained 100 pM ascorbic acid, which had no effect by itself in control experiments. Dopamine and Rp-and Sp-CAMPS were from Research Biochemicals (Natick, MA).