AJP - Regulatory, Integrative and Comparative Physiology, Vol 252, Issue 6 1039-R1045, Copyright © 1987 by American Physiological Society
Activation of neurosecretory cells by osmotic stimulation of anteroventral third ventricle
K. Honda, H. Negoro, T. Higuchi and Y. Tadokoro
Extracellular action potentials of paraventricular neurosecretory cells
were obtained from urethan-anesthetized rats during microinjection of a
hyper- or hypotonic solution into the anteroventral third ventricle (AV3V),
third ventricle, or the vicinity of the recording site. The injection of a
0.2-microliter NaCl solution with a concentration range from 0.16 to 0.8 M
into the AV3V excited most of the neurons tested. However, the magnitude of
the response was dose related. In most cases, arterial blood pressure
recorded simultaneously with the excitatory response of the neuron did not
change after the injection. Distilled water (0.2 microliter) was injected
into the AV3V after the intraperitoneal injection of a 1.5 M NaCl solution
(1 ml), which decreased the firing rate in 67% of the neurons tested. The
small volume (0.2 microliter) of hypertonic saline, which was effective
when injected into the AV3V, excited none of the neurons tested when
injected into the third ventricle or the vicinity of the recording site.
These results strongly suggest that the AV3V is sensitive to the osmotic
stimulus within a physiological range and that the region plays an
important role as an osmoreceptor site for the osmoregulation of
paraventricular neurosecretory cells.
