These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Dopamine inhibits a sustained calcium current through activation of alpha adrenergic receptors and a GTP-binding protein in adult rat sympathetic neurons.
    Author: Aguayo LG, Grossie J.
    Journal: J Pharmacol Exp Ther; 1994 May; 269(2):503-8. PubMed ID: 8182518.
    Abstract:
    Although it is suspected that dopamine (DA) inhibits a Ca++ current in sympathetic neurons, the receptor and the Ca++ channel type involved are still unknown. We found that DA caused a reversible inhibition on omega-conotoxin sensitive and resistant Ca++ currents in the superior cervical ganglion (SCG). The concentration of DA that induced half-maximal inhibition was 3.0 microM. The DA receptor agonists (+/-)-SKF-38393 (D1 type) and quinpirole (D2 type) appeared unable to induce an inhibition of the Ca++ current. Furthermore, the receptor antagonists SCH-23390 (D1 type) and (-)-sulpiride (D2 type) did not prevent the inhibitory effect of DA. This suggests that the effect of DA on the Ca++ current was not due to activation of DA receptors. The inhibition of the Ca2++ current by DA was reduced by application of 1 microM phentolamine, a nonselective alpha adrenergic antagonist, and by prazosin and yohimbine, alpha-1 and alpha-2 receptor antagonists, respectively. The beta adrenergic receptor antagonist propranolol did not block the effect of DA. A guanine nucleotide-binding protein appears to be involved in the activation of adrenergic receptors by DA. The addition of GTP-gamma-S (0.1 mM) to the intracellular solution produced an effect similar to that of DA. Incubation of sympathetic neurons with pertussis toxin reduced the effect of DA by 90%. The results indicate that DA reduces the number of available Ca++ channels in sympathetic neurons by activation of alpha adrenergic receptors, which are associated with a pertussis-sensitive GTP-binding protein.
    [Abstract] [Full Text] [Related] [New Search]