Presynaptic inhibition by dihydroergotoxine of the response to peripheral sympathetic nerve stimulation in rats.
Dihydroergotoxine decreased the heart rate in both intact and pithed rats but increased blood pressure in pithed rats only. Dihydroergotoxine did not inhibit the postsynaptic effect of isoprenaline and noradrenaline but reduced the neurally induced pressor responses and tachycardia in the rat. The first effect was antagonized by sulpiride, and the second by yohimbine. It was concluded that dihydroergotoxine stimulates presynaptic alpha 2-adrenoceptors at the cardioaccelerator nerve endings, and presynaptic dopamine receptors at the sympathetic terminations innervating the vascular bed.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D004088:Dihydroergotoxine / Q000494:pharmacology*; D004558:Electric Stimulation; D006339:Heart Rate / Q000187:drug effects; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011941:Receptors, Adrenergic / Q000187:drug effects*; D013564:Sympathetic Nervous System / Q000187:drug effects*
D011941:Receptors, Adrenergic; D004088:Dihydroergotoxine; D007545:Isoproterenol; D009638:Norepinephrine