NEUROTROPHIN REGULATION OF CORTICAL DENDRITIC GROWTH REQUIRES ACTIVITY

Neurotrophins have been proposed to mediate several forms of activity- dependent competition in the central nervous system. A key element of such hypotheses is that neurotrophins act preferentially on active neu rons; however, little direct evidence supports this postulate. We ther efore examined, in ferret cortical brain slices, the interactions betw een activity and neurotrophins in regulating dendritic growth of layer 4 pyramidal neurons. Inhibition of spontaneous electrical activity, s ynaptic transmission, or L-type calcium channels each prevented the ot herwise dramatic increase in dendritic arborizations elicited by brain -derived neurotrophic factor. In developing cortex, this requirement f or conjoint neurotrophin signaling and activity provides a mechanism f or selectively enhancing the growth and connectivity of active neurons .