The influence of intracerebroventricular infusions on osmotically induced urine excretion in the pigeon (Columba livia)

This study deals with the influence of intracerebroventricular (ICV) infusions on urine volume and electrolyte excretion in response to a peripherally administered osmotic load in conscious behaving pigeons. The ICV infusions were intended to influence the cerebrospinal fluid (CSF) sodium (Na+) concentration that would have been increased by the hypertonic NaCl or sucrose solutions infused intravenously (IV). Urine and electrolyte excretion following IV infusion of 0.5 M NaCl were enhanced by simultaneous ICV infusion of 0.3 M NaCl and essentially unchanged by ICV infusions of 0.3 M or 0.9 M sucrose, or water. Infusions (ICV) of water, isotonic and hypertonic NaCl or sucrose did not significantly influence urine and electrolyte excretions following IV infusion of 1.0 M NaCl or sucrose (except K+ in the case of ICV/IV sucrose). Isotonic (0.3 M) or hypertonic (0.9 M) sucrose infused ICV enhanced urine and electrolyte excretion following IV infusion of 1.5 M sucrose. Similar amounts of sodium were excreted following IV infusion of 0.5 M NaCl, 1.0 M sucrose or 1.5 M sucrose plus the ICV infusions. The results suggest that the concentration of Na+ in the CSF is one of the factors that play a role in urine and electrolyte excretion following IV administration of osmotic stimuli in the pigeon.