Introduction

Developmental psychopharmacology takes place within the context of developmental neurobiology. Normal maturation of the brain is characterized by complex anatomic, molecular, and organizational changes which are required to prepare the individual for optimal adaptive behavior (Chugani et al., 1996). The practicing clinician should strive to understand evolving psychopathology and psychopharmacologic treatments within this context as both may affect central nervous system (CNS) developmental processes. Advances in our understanding of brain development in experiments derived from both animals and humans have started to shed some light on certain underlying principles which could serve as the rational basis for developmental psychopharmacology. In this chapter, we will review briefly the normal development of the CNS, developmental aspects of neurotransmitters and receptors, developmental neuroimaging, and experimental studies involving psychotropic compounds in young animals.

Microdevelopment

Models and concepts

It is well recognized that various neuroanatomic regions and neurotransmitter systems develop at different rates and mature at different times (Teicher and Baldessarini, 1987). Neural development can be traced through four overlapping processes: cell birth (neurogenesis), cell migration, formation of connectivity (including elaboration of processes, synapse formation, cell death, and axonal regression), and myelination (Insel, 1995). In many areas of the immature brain, more neurons and neurites are produced than in the mature brain. Significant numbers of neurons die prenatally whereas neurite elimination goes on at least until late childhood or early adolescence (Huttenlocher, 1979; Rakic et al., 1986), with myelination extending across the life cycle (Benes, 1998; Yakovlev and Lecours, 1967).