Lesions in the septal nuclei of the rat raise mean systemic arterial pressure and prevent the development of sound-withdrawal hypertension

Abstract

Abstract Midline lesions in the hippocampal commisure involving the bed nucleus (I) in the forebrains of rats, and lesions which destroyed the medial septal nuclei (III), caused mean systemic arterial pressure to rise by 30–40 mm Hg in female rats of an inbred hypertensive Wistar strain. Lesions involving the anteromedial portions of both lateral septal nuclei (II) raised mean arterial pressure by 10–20 mm Hg. After pentolinium, mean arterial pressure remained raised, by approximately 20 mm Hg, in the 7th postoperative week after lesions I, II and III. The mean systemic arterial pressures of intact and shamlesioned rats rose by 30–40 mm Hg when exposed to reduction of sound level from 65–85 to 35–45 db for 5–6 weeks: this treatment did not influence the mean arterial pressures of rats with lesions I, II or III. The pressor effects of (-)-noradrenaline (0ṁ25 μg), tyramine (25 μg), angiotensin (10 ng) and vasopressin (0ṁ2 mU) did not differ in ganglion blocked sham-lesioned and lesioned animals. Organ/body weight ratios did not increase in the lesioned animals; overall, both the pituitary and adrenal weights were just significantly (P > 0ṁ05) reduced. Lesions II and III caused a significant reduction in kidney weight and lesion II a significant rise in the index of thyroid activity.