Biomedical subjects
Publications and source records attributed to V VARAGIC.
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Cooling the guinea-pig ileum to 19 to 26 degrees abolished the emptying phase of the peristaltic reflex. The effects of cooling to 10 degrees were usually reversible, but cooling to 5 degrees for 3 to 8 hr. produced an irreversible decrease in or abolition of the emptying phase. 5-Hydroxytryptamine (5-HT) added in low concentrations to the fluid outside the intestine restored slight peristaltic activity after this activity had been abolished by cooling. If the peristalsis had been depressed but not abolished by cooling, 5-HT in the bath sometimes abolished it. 5-HT introduced into the lumen of the cooled gut regularly restored or increased peristaltic activity. This action was prevented by previous injection of 2-bromolysergic acid diethylamide into the lumen. It is suggested that, when introduced into the lumen, 5-HT may sensitize the sensory receptors in the mucosa of the cooled intestine. When applied outside, 5-HT may facilitate transmission at synapses involved in the peristaltic reflex arc, the excitability of which has been depressed by cooling.
The introduction of substance P into the lumen of the isolated guinea-pig ileum caused an increase in the number and amplitude of the peristaltic waves. In preparations in which the peristaltic reflex was abolished, by fatigue, by external or internal application of 5-hydroxytryptamine, or by lowering the temperature of the bath, the introduction of substance P into the lumen of the intestine restored peristalsis. This effect of substance P was absent in preparations in which the mucous membrane was removed. Hexamethonium abolished the effect of substance P on peristalsis. It is concluded that substance P acts on the afferent nervous elements of the peristaltic reflex arc, possibly on the sensory receptors.
Small amounts of eserine salicylate (10 to 20 mug.) regularly caused a rise of blood pressure in non-anaesthetized rats. Neostigmine methylsulphate in doses from 1 to 10 mug./animal usually caused a fall of blood pressure, or no change was observed; only in a few experiments was a rise of blood pressure noted. The pressor effect of eserine was abolished by atropine and reduced or abolished by yohimbine and phentolamine. Adrenalectomy did not change the response to eserine. The present experiments do not contradict earlier statements that the pressor effect of eserine was due to the discharge of impulses from a centre or centres in the central nervous system.
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