[Histaminergic neuron system and neural plasticity].

The histaminergic neuron system is located in the posterior hypothalamus as a tuberomammillary nucleus (TM) and sends nerve fibers with varicosities to almost all regions of the brain from the olfactory bulb to the spinal cord, suggesting that this neuron system is involved in the control of the activities of the whole brain. We examined the effects of pharmacological manipulations of the histaminergic neuron system on various kinds of invasive stimuli, such as methamphetamine behavioral sensitization (reverse tolerance), neuronal cell death caused by brain ischemia and electroconvulsive shock. Nerve degeneration caused by chemical and physical denervation caused an increase in H3 receptors in the postsynaptic sites. It seems likely that histamine functions in a direction to protect against various stimuli to maintain homeostasis, which is in good agreement with the morphological characteristics described above.