AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 4 973-R981, Copyright © 1990 by American Physiological Society
Differential osmoresponsiveness of periventricular neurons in duck hypothalamus
K. Kanosue, H. Schmid and E. Simon
Max-Planck-Institut fur Physiologische und Klinische Forschung, Bad Nauheim, Federal Republic of Germany.
Single-unit responses to osmotic stimulation were recorded extracellularly
in slice preparations from the duck's hypothalamus in the periventricular
layer (pl), magnocellular center (mc), and deep periventricular neuropil of
the paraventricular nucleus (PVN). The pl neurons were located in the
dorsorostral third ventricular region of maximum osmoresponsiveness
determined in vivo. Hypertonic stimulation (+20 to +35 mosmol/kgH2O) by
excess NaCl in the incubation medium excited 25 and inhibited 4 out of 48
pl neurons. Hypotonic (-10 to -20 mosmol/kgH2O) stimulation inhibited 9 out
of 10 neurons activated by hypertonic stimulation. Hypertonic activation of
pl neurons was maintained in seven out of nine neurons when NaCl was
replaced by LiCl, but replacing NaCl by sucrose was ineffective in each of
10 neurons. Synaptic blockade (Ca2(+)-free/high-Mg2+ medium) did not
abolish hypertonic activation in 8 out of 11 pl neurons. Among 30 mc
neurons, 2 were activated and 1 inhibited by hypertonic stimulation with
NaCl (+20 to +35 mosmol/kgH2O), and among 24 neurons in the periventricular
neuropil, 2 were activated and 4 inhibited. The function of osmoresponsive
pl neurons as specific receptors would be consistent with their
morphological characteristics and with the location and functional
properties of the duck's third ventricular osmoresponsiveness in vivo.
