In order to investigate the neural mechanism of olfaction-related nystagmic response, a series of experiments has been carried out where various parts of rabbits' brains received repeated electrical stimulation. The resulting changes in nystagmic responses of the animals were observed, when they were stimulated by intravenous adrenaline and inhalation of the vapor of liquid garlic.
The results obtained were as follows:
(1) The rabbits receiving repeated electrical stimulation of the hippocampus tended to develop and /or increase nystagmic response with intravenous adrenaline. In some of them, increase and / or decrease of nystagmic responses were also seen in response to inhalation of the vapor of liquid garlic.
(2) The rabbits receiving repeated electrical stimulation of the lateral portion of the amygdaloid nucleus did not show any signs of nystagmic response with intravenous adrenaline. The same held true for inhalation of the vapor of liquid garlic.
(3) One rabbit receiving repeated electrical stimulation of the septal area had an increased nystagmic response with intravenous adrenaline. This animal also had an increased nystagmic response when he was stimulated by inhalation of the vapor of liquid garlic.
(4) The rabbits receiving repeated electrical stimulation of the habenular nucleus had significant development and / or increase of nystagmic response when intravenous adrenaline was given. These animals also developed similar nystagimic response with inhalation of the vapor of liquid garlic.
With reference to the above-mentioned results and those from our previous animal experiments, the following conclusions were drawn:
(1) The medial portion of the amygdaloid nucleus and habenular nucleus play a major role in the production of olfaction-related nystagmic response. In contrast, the roles of the hippocampus and septal area in induction of nystagmic responses due to olfaction were less obvious. No significant role of the lateral portion of the amygdaloid nucleus was attributable in the production of the nystagmus of this kind.
(2) Overexcitement of adrenergic components in the central nervous system, particularly those involved in the medial portion of the amygdaloid nucleus and habenular nucleus is an important factor for the production of olfaction-related ocular dysfunction, i.e. nystagmus.
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