Influence of environmental stimulation on neurogenesis in the adult insect brain

Abstract

Mushroom bodies are the main integrative structures of insect brain. They receive sensory information from the eyes, the palps, and the antennae. In the house cricket, Acheta domesticus, a cluster of mushroom body neuroblasts keeps producing new interneurons during an insect's life span. The aim of the present work is to study the impact of environmental stimuli on mushroom body neurogenesis during adulthood. Crickets were reared either in an enriched environment, where they received complex environmental and congeneric stimulations or isolated in small cages and deprived of most visual, auditory, and olfactory stimuli. They then were injected with a S‐phase marker, 5‐bromo, 2′‐deoxyuridine (BrdU) and sacrificed at different periods of their life. Neurogenesis and cell survival were estimated by counting the number of BrdU‐labeled cells in the mushroom bodies. Environmentally enriched crickets were found to have an increased number of newborn cells in their mushroom bodies compared with crickets housed in cages with an impoverished environment. This effect of external factors on neurogenesis seems to be limited to the beginning of imaginal life. Furthermore, no cell loss could be detected among the newborn neurons in either environmental situation, suggesting that cell survival was not affected by the quality of the environment. Considering vertebrate studies which showed that enriched environment increases hippocampal cell survival and improves animal performances in spatial learning tests, we suggest that the increased number of interneurons produced in an integrative brain structure after exposure to enriched environment could contribute to adaptive behavioral performances in adult insects. © 2000 John Wiley & Sons, Inc. J Neurobiol 45: 162–171, 2000

Neurogenic and Neuroendocrine Effects of Goldfish Pheromones

“…Several environmental factors, such as seasonal variations in temperature and photoperiod, and sensory inputs influence adult neurogenesis (Cayre et al, 2002). Enriched sensorial and social environments enhanced neurogenesis in cricket mushroom bodies (Scotto Lomassese et al, 2000), crayfish brain (Sandeman and Sandeman, 2000), and the hippocampus of birds and rodents (Kempermann et al, 1997(Kempermann et al, , 1998Patel et al, 1997;Gould et al, 1999;van Praag et al, 1999a,b;Ambrogini et al, 2000). Our finding of PGF 2␣ -induced neurogenesis in goldfish brain suggests that an enriched chemical environment may also promote adult neurogenesis.…”

“…Adult neurogenesis in both vertebrates and invertebrates appears to be regulated by internal factors such as hormones, neurotransmitters, and growth factors, and by external factors such as environmental cues (Scotto Lomassese et al, 2000;Cayre et al, 2002). Pheromones are a class of environmental cues that are known to exert profound effects in insect brains (Grozinger et al, 2003Alaux and Robinson, 2007;Beggs et al, 2007;Grozinger and Robinson, 2007;Vergoz et al, 2007).…”

Agonistic behavior enhances adult neurogenesis in maleAcheta domesticuscrickets

“…BrdU, a thymidine analog, becomes incorporated into the DNA of dividing cells during the S phase of mitosis. This is the same BrdU concentration used by Myriam Cayre and colleagues in their pioneering studies on neurogenesis in adult crickets (Cayre et al, 1996;Scotto-Lomassese et al, 2000). The solution was heated to 50°C in order for the BrdU to completely dissolve but was allowed to cool before injection.…”

“…Many also regulate neuroblast proliferation and neurogenesis in adult crickets Cayre et al, 2007). For example, the proliferation rate of MB neurogenic cells of female crickets housed in enriched environments was greater than for females in impoverished environments (Scotto-Lomassese et al, 2000). Visual and olfactory stimuli enhance proliferation of these cells, while sensory deprivation decreases it .…”

A putative link of PUFA, GPR40 and adult-born hippocampal neurons for memory

“…Thus, the formation, modification and elimination of synapses, being the direct result of removal, generation and replacement of entire neurons, can play a fundamental role in learning and memory. Hippocampal neurogenesis can be altered by various hormones (Gould et al, 1998, Shingo et al, 2003, exercise (Kempermann et al, 1997b, van Praag et al, 1999a and enriched environments in both vertebrates and invertebrates (van Praag et al, 1999b, Scotto-Lomassese et al, 2000. Then, adult neurogenesis may, in fact, have a predominant role rather for modifying circuitry related to the processing of sensory information (Lindsey and Tropepe, 2006).…”