Whilst it is universally accepted that the energy support of the brain is glucose, the form in which the glucose is taken up by neurones is the topic of intense debate. In the last few decades, the concept of lactate shuttling between glial elements and neural elements has emerged in which the glial cells glycolytically metabolise glucose/glycogen to lactate, which is shuttled to the neural elements via the extracellular fluid. The process occurs during periods of compromised glucose availability where glycogen stored in astrocytes provides lactate to the neurones, and is an integral part of the formation of learning and memory where the energy intensive process of learning requires neuronal lactate uptake provided by astrocytes. More recently sleep, myelination and motor end plate integrity have been shown to involve lactate shuttling. The sequential aspect of lactate production in the astrocyte followed by transport to the neurones is vulnerable to interruption and it is reported that such disparate pathological conditions as Alzheimer’s disease, amyotrophic lateral sclerosis, depression and schizophrenia show disrupted lactate signalling between glial cells and neurones.

Stress is a potent environmental factor that can confer potent and enduring effects on brain structure and function. Exposure to stress during early life (ELS) has been linked to a wide range of consequences later in life. In particular, ELS exerts lasting effects on neurogenesis in the adult hippocampus, suggesting that ELS is a significant regulator of adult neural stem cell numbers and function. Here, we investigated the effect of ELS on cell proliferation and the numbers of neural stem/precursor cells in another neurogenic region: the hypothalamus of adult mice. We show that ELS has long-term suppressive effects on cell proliferation in the hypothalamic parenchyma and reduces the numbers of putative hypothalamic neural stem/precursor cells at 4 months of age. Specifically, ELS reduced the number of PCNA þ cells present in hypothalamic areas surrounding the 3rd ventricle with a specific reduction in the proliferation of Sox2þ/Nestin-GFP þ putative stem cells present in the median eminence at the base of the 3rd ventricle. Furthermore, ELS reduced the total numbers of b-tanycytes lining the ventral 3rd ventricle, without affecting a-tanycyte numbers in more dorsal areas. These results are the first to indicate that ELS significantly reduces proliferation and b-tanycyte numbers in the adult hypothalamus, and may have (patho)physiological consequences for metabolic regulation or other hypothalamic functions in which b-tanycytes are involved.

Early life stress (ELS) is a potent environmental factor that can confer enduring effects on brain structure and function. Exposure to stress during early life has been linked to a wide range of physiopathological consequences later in life. In particular, ELS has been shown to have lasting effects on neurogenesis in the adult brain, suggesting that ELS is a significant regulator of adult neural stem cell function. Here, we investigated the effect of ELS on the numbers and proliferation of neural stem cells in the hypothalamus of adult mice.We show that ELS has long term negative effects on hypothalamic neural stem cell numbers and on their proliferation. Specifically, ELS reduced the total numbers of PCNA+ cells present in hypothalamic areas surrounding the 3 rd ventricle; the numbers of PCNA+/Sox2+/Nestin-GFP+ cells present in the medial eminence at the base of the 3 rd ventricle; and the number of β-tanycytes around the ventral 3rd ventricle, without affecting the numbers of α-tanycytes in more dorsal areas. These results suggest that a reduction of proliferation and tanycyte numbers contributes to the effects of ELS on the hypothalamus and its consequent physiological alterations. 7