Brain activity determines IGF-I trophic input to neurons

T. NISHIJIMA *, J. PIRIZ * (*EQUAL CONTRIBUTORS), H. SOYA, A. NUÑEZ, I. TORRES ALEMAN

Washington

Congreso; Annual Meeting of the Society for Neuroscience; 2008

Society for Neuroscience

Engaged mental activity is a salient feature of putative neuroprotective life-styles such as higher education or an active social life. However, the mechanisms underlying the beneficial actions of sustained brain activity are just beginning to emerge. In the present study we started to determine the potential role of blood-borne insulin-like growth factor I (IGF-I), a potent neuroprotective hormone, in the beneficial effects of brain activity. Other life-style factors affecting brain function such as physical activity or diet involve serum IGF-I. We found that systemic IGF-I entered into activated brain areas such as cerebellum or cortex, regardless of the type of stimulation employed. Furthermore, in somatosensory cortex entrance of systemic IGF-I paralleled local increases in cerebral blood flow elicited by stimulation at 2 Hz (but not at 5 Hz) of the whisker pad. In turn, activity-regulated entrance of peripheral IGF-I influenced neuronal activity as infusion of an IGF-I receptor blocker in the stimulated barrel cortex resulted in marked decreases in neuronal output. Thus, activity-dependent entrance of blood-borne IGF-I may underlie beneficial effects of environmental enrichment on brain function.