Previous experiments in rodents showed that ablation of the septal brain region caused hyperdipsia. We investigated which part of the septal region needs ablation to produce hyperdipsia in sheep, and whether increased drinking was a primary hyperdipsia. Following ablation of the medial septal region (n = 5), but not parts of the lateral septal region (n = 4), daily water intake increased from ∼2.5-5 litres/day up to 10 litres/day for up to 3 months post-lesion. In hyperdipsic sheep, plasma osmolality increased on the first day post-lesion and body weight fell, suggesting that initial hyperdipsia was secondary to fluid loss. However hyperosmolality was not sustained long-term and plasma hypo-osmolality persisted from 0.5 to 3 months post-lesion. Acute dipsogenic responses to intravenous hypertonic saline, intravenous or intracerebroventricular angiotensin II, water deprivation for 2 days, or feeding over 5 hours were not potentiated by medial septal lesions, showing that the rapid pre-systemic inhibitory influences that cause satiation of thirst upon the act of drinking were intact. However, hyperdipsic sheep continued to ingest water when hyponatremic (plasma [Na] was 127-132 mmol/l) and plasma osmolality was 262-268 mosmol/kg due to retention of ingested fluid resulting from intravenous infusion of vasopressin administered to maintain a basal blood level of antidiuretic hormone. The results show that septal lesion-induced hyperdipsia is not due to disruption of acute pre-systemic influences associated with drinking water that initiates rapid satiation of thirst. Rather, inhibitory influences of hyponatremia, hypo-osmolality or hypervolemia on drinking appear to be disrupted by medial septal lesions.

先前在啮齿动物中的实验表明，中隔脑区的消融会导致多饮。我们调查了中隔区域的哪一部分需要消融才能在绵羊中产生多饮，以及饮酒增加是否是原发性多饮。在消融中间隔区域（n = 5）后，但不是部分侧间隔区域（n = 4），每日饮水量从 ~2.5-5 升/天增加到 10 升/天，持续长达 3 个月损伤后。在多饮绵羊中，血浆渗透压在损伤后第一天增加，体重下降，表明最初的多饮继发于体液流失。然而，高渗不能长期持续，血浆低渗从损伤后 0.5 到 3 个月持续存在。对静脉内高渗盐水的急性双原性反应，静脉内或脑室内血管紧张素 II、禁水 2 天或喂食超过 5 小时均未因中间隔病变而增强，表明饮酒行为引起口渴的快速全身前抑制影响是完整的。然而，当低钠血症（血浆 [Na] 为 127-132 mmol/l）和血浆渗透压为 262-268 mosmol/kg 时，由于静脉输注加压素以维持基础水平，导致摄入的液体滞留，高尿症绵羊继续饮水。血抗利尿激素水平。结果表明，中隔损伤引起的多饮不是由于与饮用水相关的急性全身性影响的破坏，后者会引发口渴的快速满足。相反，低钠血症的抑制作用，