Original Article

Neuropsychopharmacology (1999) 21, 33S–45S. doi:10.1016/S0893-133X(99)00022-6

Serotonin Neurons, Neuroplasticity, and Homeostasis of Neural Tissue

Efrain Charles Azmitia Ph.D1

1Department of Biology, New York University, New York, NY USA

Correspondence: Efrain Charles Azmitia, Department of Biology, New York University, 100 Washington Square East, New York, New York 10003–6688

Received 10 December 1998; Revised 5 February 1999; Accepted 8 February 1999



Homeostasis is the process by which the internal milieu of the body is able to maintain equilibrium in the face of constant insults from the external world. Endocrine, immune, and vascular systems play pivotal roles in adjusting internal biochemical reactions to counteract assaults from the outside. Despite the vast accumulation of data over the last 50 years, a role for serotonin in brain homeostasis has not been proposed. In this chapter I will review the plasticity and anatomy of serotonergic neurons in integrating external sensory and motor systems as well as internal endocrine, glial and vascular signals with the various cellular elements comprising neural tissue. Steroids and neuropeptides have both been shown to alter the morphology of serotonergic neurons. In turn, alterations in serotonin levels in the adult brain can change the morphology of its target cells. A pivotal role for serotonin in the homeostasis of neural tissue is consistent with the function of serotonin throughout evolution and explains the large number of biological systems, behavioral activities, and clinical diseases associated with serotonergic neurons.


Raphe; Co-localization; Ultrastructure; Evolution; Neuropeptide; Review

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