Volume 16, Number 17,
Issue of September 1, 1996
pp. 5547-5554
Copyright ©1996 Society for Neuroscience
Evidence for Differential Control of Posterior Hypothalamic,
Supramammillary, and Medial Mammillary Theta-Related Cellular Discharge
by Ascending and Descending Pathways
Received April 18, 1996; revised June 5, 1996; accepted June 11, 1996.
Ian J. Kirk,
Scott D. Oddie,
Jan Konopacki, and
Brian
H. Bland
Department of Psychology, Behavioral Neuroscience Research Group,
University of Calgary, Calgary, Alberta, Canada T2N 1N4
Single-unit discharge was recorded from cells in the posterior
hypothalamic nucleus (PH), supramammillary nucleus (SuM), and medial
mammillary nucleus (MM) during hippocampal theta (
) elicited by
stimulation of the reticular nucleus pontis oralis (RPO). In agreement
with previously published work,
-related cells in the PH (12 cells)
were all classified as tonic
-ON (increased tonic discharge rate
during hippocampal
), whereas those in the SuM (9 cells) and MM (15 cells) were all classified as phasic
-ON (rhythmic discharge, in
phase with ongoing
). The effect of RPO stimulation on cell
discharge was tested after hippocampal
was abolished by infusion of
procaine into the medial septum/vertical limb of the diagonal band. The
RPO-elicited discharge patterns of all PH tonic
-ON cells and all
SuM phasic
-ON cells survived septal procaine infusion. Further, the
discharge rate of PH cells and the frequency of burst discharge of SuM
cells during RPO stimulation both increased after the infusion. In
contrast, septal procaine infusion abolished the RPO-elicited rhythmic
discharge pattern in MM phasic
-ON cells and attenuated their
discharge rates. These results indicate that the PH and SuM form parts
of an ascending system mediating hippocampal
, whereas the MM
receives (and perhaps relays to other parts of the limbic system)
rhythmic input descending from the septo-hippocampal system. In
addition, PH and SuM receive descending inputs that limit the discharge
rates of their
-related cells during hippocampal
.
Key words:
intraseptal;
procaine;
hippocampal theta;
supramammillary
nucleus;
posterior hypothalamic nucleus;
medial mammillary nucleus;
rhythmic cell discharge