Inhibition of natidiuretic hormone secretion by intracarotid infusions of slightly hypertonic non-electrolyte solutions

Posterior pituitary function in health and disease

This chapter has reviewed briefly the neuroanatomy relevant to the synthesis and release of AVP and OXT. Osmoregulation and baroregulation of AVP secretion has been discussed in detail, emphasizing the importance of osmotic control under normal physiological conditions. The remainder of the text has covered the two major pathophysiological disturbances of AVP secretion. In considering diabetes insipidus a pragmatic approach has been taken in the differentiation of the causes of polyuria and its treatment. A similar approach has been applied to the syndrome of inappropriate antidiuresis. Brief mention was made of the function of OXT.

Cellular and extracellular dehydration, and angiotensin as stimuli to drinking in the common iguana Iguana iguana

1. After water deprivation, the iguana promptly drank slightly more than enough water to restore the body fluids to isotonicity even under conditions of hypervolaemia. 2. In response to systemic injections of hypertonic solutions of NaCl and sucrose, the iguana drank and retained enough water to dilute the injected load to isotonicity irrespective of whether water was offered immediately or after 3 hr, and irrespective of whether the solute was administered I.V. or I.P. 3. Hypertonic solutions to glucose, urea, sorbitol and KCl caused little drinking. 4. The long latencies to drinking after hypertonic loads, which were not dependent on the nature of the solute, the route of administration or the dosage, were shown not to be a result of slow distribution of the solute throughout the body fluids. 5. Clearance of injected solutes via renal and extra-renal (nasal salt gland) routes was negligible during the 6 hr experimental period. 6. Measurements of plasma [Na], haematocrit, osmotic pressure and inulin space showed that the iguana drank, in response to cellular dehydration, enough water to restore the intracellular fluid volume to normal. 7. We conclude that, in response to substances which dehydrate cells, the iguana regulates its body osmolality precisely and efficiently provided it is able to do so by drinking. In this respect the responses of the iguana are similar to those of the nephrectomized rat since, in the short term, both rely exclusively on drinking to restore cellular water to normal. 8. The iguana also drinks in response to extracellular dehydration produced by hyperoncotic peritoneal dialysis, and in response to I.P. angiotensin II.