The effects of bromocriptine on pre-synaptic and post-synaptic alpha-adrenoceptors in the mouse vas deferens.

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Gibson A, Samini M

The effects of bromocriptine on pre-synaptic and post-synaptic alpha-adrenoceptors in the mouse vas deferens.

J Pharm Pharmacol. 1979 Dec;31(12):826-30.

PubMed ID

43367 [ View in PubMed

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Abstract

Noradrenaline (NA) and dopamine (DA) contracted the mouse vas deferens and reduced the responses to low frequency nerve stimulation (0.1 Hz). The relative potencies of antagonists suggested that these effects were due to stimulation of post-synaptic and pre-synaptic alpha-adrenoceptors respectively. Bromocriptine produced a non-competitive antagonism of contractile responses to NA (pD2' = 7.6) and DA (pD2' = 8.0) but had no effect on responses to carbachol. Bromocriptine also reduced single twitch responses of the vas to low frequency field stimulation (0.1 Hz), but did not affect stimulation at higher frequencies (1--20 Hz). Yohimbine selectively and rapidly reversed the inhibiting effects of bromocriptine on single twitches, although they could not easily be reversed by washing. Bromocriptine produced a yohimbine-reversible reduction in the stimulated overflow of tritium from vasa previously loaded with 3H--NA. Thus the mouse vas deferens does not appear to contain specific DA receptors and the results suggest that bromocriptine acts as a pre-synaptic alpha-adrenoceptor agonist and post-synaptic alpha-adrenoceptor antagonist in this tissue.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Bromocriptine	Alpha-1A adrenergic receptor	Protein	Humans	Unknown	Antagonist Agonist	Details
Bromocriptine	Alpha-1B adrenergic receptor	Protein	Humans	Unknown	Antagonist Agonist	Details