イヌの骨盤神経膀胱枝, 陰部神経尿道枝の遠心性活動に対する嗅結節電大刺激の効果

Abstract

Experiments were performed to elucidate the effects of stimulation of the olfactory tubercle on the urinary bladder and external urethral sphincter in 31 dogs anesthetized with ketamine and alpha-chloralose and immobilized with gallamine. The hypogastric nerve was severed in all dogs, and the bladder was filled with Tyrode's solution under constant pressure (15-20 cmH2O). The outflows of the pelvic vesical branch (PV) and the pudendal urethral branch (PU) and isotonic vesical contractions were recorded simultaneously. Stimulation (5-100 Hz, 3 msec, 0.2 mA) was applied through a unipolar platinum electrode (50 microns, in diameter) inserted into the olfactory tubercle from the ventral surface. Olfactory tubercle stimulation elicited PV excitation (bladder contraction) and concomitant PU inhibition (urethral relaxation), but no reverse effect. Electrical stimulation was applied to the excitatory points at varied frequencies (5-100 Hz). PV excitation and bladder contraction were produced at 10, 20, 50 and 100 Hz, but not at 5 Hz. In another group, the vesicopressor pathway from the tubercle was investigated by partial sectioning of the brain stem in dogs from which the left fore- and mid-brain had been previously removed. The vesicopressor response induced by tubercle stimulations was not abolished by sectioning of the medial preoptic area, medial hypothalamus or periaqueductal grey, but was abolished by sectioning of the lateral preoptic area, lateral hypothalamus or ventral mesencephalic tegmentum, respectively. At the rostral pontine level, the response was abolished by partial sectioning of the lateral part of the pontine reticular formation ipsilateral to the stimulation.