Acetylcholinesterase neurons in the lateral hypothalamus project to the spinal cord

The possibility that cholinergic neurons of the basal forebrain project to the spinal cord was investigated utilizing the retrograde transport of bisbenzimide and [3H]choline as well as acetylcholinesterase histochemistry. A striking similarity was observed in the distributions of lateral hypothalamic neurons labeled with bisbenzimide and acetylcholinesterase. Only a small number of these neurons contained both markers, suggesting the possibility of a small cholinergic projection from the lateral hypothalamus to the spinal cord. The use of [3H]choline to test this hypothesis yielded negative results. Thus the present observations indicating that lateral hypothalamic neurons are cholinoceptive, are consistent with choline acetylcholinesterase immunohistochemical studies. The potential for basal forebrain cholinergic neurons to influence spinal autonomic activity via the lateral hypothalamus is discussed.