Journal of Neurophysiology, Vol 50, Issue 3 609-617, Copyright © 1983 by APS
Response characteristics of lateral hypothalamic neurons to odors in unanesthetized rabbits
S. Kogure and N. Onoda
Extracellular responses of 103 neurons to eight odors were studied in the
lateral hypothalamic area (LHA) of unanesthetized rabbits. In response to
electrical stimulation of the olfactory bulb (OB), 97 units were excited
with latencies of 3.7-68.0 ms (mean, 19.4 ms) and the activity of 6 units
was suppressed. In the LHA, 90 units of 103 were found that responded to
from one to eight odors. The number of units that responded to three odors
was the most numerous (22%) among these odor-sensitive units. Lateral
hypothalamic (LH) neurons showed high response probabilities to cineole
(0.72), cyclotene (0.68), and isovaleric acid (0.54). Of the recorded
units, 94% showed an excitatory-type response to both electrical
stimulation of the OB and odor stimuli of the olfactory mucosa, while only
6% showed an inhibitory-type response to both stimuli. These results
suggest that the olfactory effect on the LHA is predominantly excitatory.
Responses to a concentration series of odors were examined in 24 LH
neurons. In most cases, response intensity did not increase monotonically
with increasing odor concentration. Instead, the concentration-response
curves of most units showed a peak or inflections during the concentration
series. Compared with results obtained from other olfactory structures in
different species, it appears that LH neurons do not contribute much to
odor discrimination in rabbits.
