Histamine immunoreactive neurons in the brain stem of the rabbit

Distribution of histamine-like immunoreactive (HA-LI) neurons in the rabbit brain stem was demonstrated by histamine antiserum. A number of HA-LI cell bodies were localized in the tuberomammillary nucleus of the posterior hypothalamus. A dense to moderate amount of HA-LI fibers was found distributed in the raphe nuclei, the inferior olive, the nucleus of the solitary tract, vestibular nuclei, and the paragigantocellular reticular nucleus in the medulla oblongata, and the parabrachial nuclei, the Klliker-Fuse nucleus, the pontine nuclei, and the locus coeruleus in the pons. HA-LI axons synapsed on dendrites of neurons in the nucleus of the solitary tract. This evidence suggests that histaminergic neurons control neuronal activity through synaptic transmission in the lower brain stem.