Gastric vasodilator and motor responses to splanchnic stimulation and tachykinins in the dog.

1. Gastric blood flow and motor responses to greater splanchnic nerve stimulation and intra-arterial injection of tachykinins were studied in anaesthetized dogs. 2. Splanchnic nerve stimulation (40 V, 10 Hz) with pulse durations of 0.05 and 1 msec caused a gastric relaxation and contraction, respectively. Both types of stimulation produced a decrease followed by an increase in blood flow. The responses to stimulation with a pulse duration of 0.05 msec were inhibited by hexamethonium. 3. After treatment with hexamethonium, stimulation with 1 msec caused frequency-dependent gastric contraction and vasodilation. Both responses had two components, sensitive and resistant to atropine. 4. Intra-arterial injection of substance P (SP), neurokinin A (NKA), neurokinin B (NKB), physalaemin (PHY) or eledoisin (ELE) elicited dose-dependent gastric contraction and vasodilation. The order of potency for contraction was SP = PHY = ELE = NKA >> NKB and that for vasodilation was SP = PHY > ELE > NKA > NKB. 5. Atropine partly inhibited the tachykinin-induced gastric contraction but not gastric vasodilation. Spantide partly inhibited the atropine-resistant vasodilation but not contraction in response to splanchnic nerve stimulation and SP. 6. It is concluded that splanchnic nerve stimulation produced cholinergic and SPergic vasodilation after ganglionic blockade in the dog stomach.