AJP - Regulatory, Integrative and Comparative Physiology, Vol 251, Issue 5 823-R832, Copyright © 1986 by American Physiological Society
Contribution of zona incerta to osmotically induced drinking in rats
D. Mok and G. J. Mogenson
Spontaneous extracellular activity was recorded from single neurons in the
rostral zona incerta (ZI) of urethan-anesthetized rats. Ventricular
injections of hyperosmotic saline (1 or 2 microliter of NaCl solutions with
osmolarities of 0.6 or 1.2 osmol/l) and distilled water (1 or 2 microliter)
at the level of the anteroventral third ventricle (AV3V) changed the firing
rate of ZI neurons. By comparison, ventricular injections of osmotic
solutions at the level of the dorsal third ventricle were relatively
ineffective. Injections of osmotic solutions (0.2 or 0.5 microliter of 1.2
osmol/l NaCl) into the medial preoptic area (MPO) also changed the firing
rate of ZI neurons, whereas control injections into the caudate putamen
were ineffective. In another series of rats, injections of procaine into
the region of the rostral ZI significantly reduced drinking to injections
of hyperosmotic saline into the ipsi- but not the contralateral MPO. The
ZI, AV3V, and MPO have previously been reported to contribute to the neural
regulation of fluid intake. These findings provide additional evidence for
a role of the ZI in drinking and suggest that part of the central pathway
for osmotic thirst involves a projection to neurons in the ZI from
osmoreceptors in the MPO.
