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The natriuretic effect of oxytocin blocks medial tuberomammillary polydipsia and polyuria in male rats
Author(s) -
Mahía Javier,
Bernal Antonio,
García del Rio C.,
Puerto Amadeo
Publication year - 2009
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2009.06686.x
Subject(s) - polydipsia , endocrinology , polyuria , medicine , thirst , oxytocin , vasopressin , hypertonic saline , lesion , natriuresis , antidiuretic , excretion , surgery , diabetes mellitus
Lesions of the tuberomammillary complex, a neuroanatomical system closely related to the hypothalamic supraoptic and paraventricular nuclei, induce strong polydipsia in male rats. It was recently demonstrated that this increase in water intake is immediate, persistent, follows circadian rhythms and appears to be related to sodium regulation. The present study found that urine osmolality was significantly lower in tuberomammillary‐lesioned animals vs. their respective controls at 8:00 h after surgery. Therefore, the aim of the present study was to examine the natriuretic effect of intraperitoneal oxytocin (OT) administration on medial ventral tuberomammillary nucleus (E3) polydipsia and polyuria of lesioned and control male rats. At 24:00 h post‐lesion, OT blocked the hyperdipsic and polyuric responses of E3‐lesioned animals but not those of non‐lesioned controls, which did however significantly increase their water intake. Moreover, urinary osmolality and sodium excretion increased in E3 ‐lesioned animals that received OT but not in lesioned controls receiving physiological saline (992 ± 187.19 vs. 215.83 ± 23.39 mOsm/kg; 1.68 ± 0.13 vs. 0.47 ± 0.1 mEq/L). At 48:00 h post‐lesion, OT administration also induced a higher intake of water and of simultaneously offered hypertonic NaCl (1.5%) in E3‐lesioned animals. These results are interpreted in terms of the hypothalamic systems involved in sodium and water homeostasis.