Neuronal histamine circuits as modulators of cognitive processes in the brain

EDGARDO O. ALVAREZ

Histamine: Synhtesis, pharmacology and clinical uses

Nova Science Publishers

Año: 2012;

Since the first isolation of histamine at about 101 years ago from the mould ergot, the imidazolamine attracted the attention of the scientific community by its surprising variety of biological effects which included stimulation of smooth muscle of the gut and respiratory tract, vasodepressor actions, increased cardiac contractility and shock-like signs when injected into animals. During many years after that, histamine was strongly associated to allergic and inflammation reactions in man and other mammals, supporting the belief that the main role of the imidazolamine was in these inflammatory reactions. Perhaps for this reason, the immunohistochemistry evidence showing the presence of histamine suggesting a physiological role of the imidazolamine in the brain was received with moderate reluctance. After the unmistakable description of histamine producing neurons in the posterior hypothalamic region of the brain, the role of histamine as neurotransmitter system was finally firmly established. In this review a brief description of the histological features of the hypothalamic tuberomammillary nucleus, the histamine-producing neurons, and the main physiological functions controlled by this nucleus will be discussed to emphasize the probable role of the histamine system on homeostasis of the body. The extensive histaminergic input to several parts of the brain will be discussed taking as a model three functional related brain structures such as the hippocampus, amygdala and the nucleus accumbens, where the histamine influence has been shown to affect several behavioral parameters related to coping behaviour and cognition. These data will be taken to give support the idea that the histaminergic neurotransmitter system in the brain represents a dynamic integrating center modulating external and internal input/output signals to generate behavioural adequate responses in animals.