Abstract

CASTRO-SIERRA, Eduardo; CHICO PONCE DE LEON, Fernando  and  PORTUGAL RIVERA, Alison. Neurotransmisores del sistema límbico. Amígdala. Segunda parte. Salud Ment [online]. 2006, vol.29, n.1, pp.51-55. ISSN 0185-3325.

Neurotransmitters of the amygdala in the limbic system include monoamines (noradrenaline [NA]) acetylcholine (ACh), corticoids and histamine.

Drugs infused into the amygdala may modulate consolidation in memory of inhibition of training directed to avoid stressful situations. Administration of antagonists of β NA receptors to the amygdala will affect retention in memory for a whole day when given immediately after training, but will have no effect when given six hours after training a test animal. Intra-amygdalar infusions of NA which may be accompanied by antagonists of those receptors will attenuate the memory disturbance. It is worth mentioning that later studies have been able to show that NA will produce an increment of memory consolidation, which will depend on the time as well as on the dose of application, when the drug is infused to the amygdala shortly after inhibition of training directed to avoid stressful situations.

The amygdala, the neocortex and the hippocampus are target regions of the frontal basal cholinergic brain system, which has different effects on cognitive functions, such as memory and learning. Any neurotransmitter with phosphorylating or dephosphorylating activity may regulate the sensitive state of ACh, as well as the functional properties of amygdalar neurons. It is possible, then, that modulation mechanisms may exist between learning and recall states in the amygdala, the neocortex and the hippocampus, which could be controlled by muscarinic acetylcholinergic receptors.

Through pre-synaptic receptors of histamine 3 (H3) and a currently unknown mechanism, histamine will decrease or increase excitatory synaptic transmission in BLA. Such histaminergic modulation of neuronal activity will play an important role in fear-related physiological and patho-physiological processes, learning and memory of emotion, and affective disturbances.

Keywords : Limbic system; neurotransmitters; noradrenaline; acetylcholine; corticoids; histamine.