  Electrophysiological time series were taken simultaneously in two locations
in the hippocampus of a rat brain previously described as receiving innervation
from the osmosensitive vasopressinergic neurons of the hypothalamus. A
hyperosmotic saline solution injection was administered during the time of the
experiment. We analyze the recorded time series using different methods. We
detect a modification of the delta and theta oscillations just after the
perturbation caused by the injection. We compare the quality and information
that each one of the methods exhibit and we analyze the characteristics of the
perturbation based on a hypothesis that the strength of the functional
connections between the vasopressinergic hypothalamic magnocellular neurons and
their target in the hippocampus is modified by the perturbation. We built a
model of the hypothetic neural connections and numerically calculate the time
series produced by the system when simulating the perturbation caused by the
saline injection. The theoretical results resemble the experimental findings
concerning the frequency and amplitude alterations of the delta and theta
bands.
