The release of endogenous histamine in distinct brain areas is modified by electrical stimulation

In anaesthetized cats, mamillary bodies, hypothalamic areas and medial amygdaloid nuclei were bilaterally superfused through push-pull cannulae and the effects of the electrical stimulation on the release of endogenous histamine were investigated. Electrical stimulation of the mamillary body increased the release of histamine in the stimulated area, as well as in the contralateral mamillary body. Electrical stimulation of the lateral hypothalamic area enhanced the histamine release in the contralateral hypothalamic area. Stimulation of the posterior hypothalamic area led to a delayed increase in the histamine release in the stimulated area. Stimulation of the medial amygdaloid nucleus reduced the release if histamine in the ipsilateral posterior hypothalamic area, while the histamine release in the contralateral lateral hypothalamic area was enhanced. The results demonstrate that electrical stimulation of distinct brain areas rich in histaminergic neurons may either increase, or decrease the release rate of histamine in the stimulated area and/or in remote brain areas.