Accordingly, our data indicate that anesthesia in young animals may induce important structural modifications that might be source of misinterpretations regarding analyses of spine number or spine morphology. The second important aspect of this work relates to the effects that anesthetics might produce in human clinical use when applied during critical periods of development in infants. Our work shows that all anesthetics tested, which all interfere with the excitation/inhibition balance, (+)-JQ1 promote a rapid increase in spine synapse density, but also affect spine morphology. These two effects were lasting for several days in young mice, and certainly contributed to modify cortical networks since many new spines turn out to be functional synapses. Although the behavioral significance of these changes remains to be determined, they might raise concern about the millions of human infants that receive general anesthesia during this developmental period every year worldwide. Indeed, an increasing number of clinical reports suggest the possibility of adverse long-term neurocognitive outcome in the population of young infants undergoing anesthesia/surgery. Altogether,ABT-199 this study demonstrates that exposure to general anesthetics during critical periods of development increases dendritic spine number and suggests a mechanism for the rapid modulation of synaptogenesis via the modulation of the excita-tion/inhibition balance by these drugs. This new mechanism is likely to play a critical role in the regulation of the formation of neural circuits and may help understand dysfunctions related to conditions under which alterations of the excitation/inhibition balance may occur. Leptospirosis is a zoonotic disease caused by pathogenic bacteria of the genus Leptospira, which are transmitted directly or indirectly from animals to humans. Leptospirosis occurs worldwide but is most common in tropical and subtropical areas with high rainfall. Globally, an estimated number of 500,000 severe cases occur annually with case fatality rates ranging from 3% to 70%, depending on the clinical manifestations.