Mechanosensitive membrane traffic and an optimal strategy for volume and surface area regulation in CNS neurons. Am. Zool

SYNOPSIS. Extrapolating from a body of work on isolated neurons, a model is suggested for how central nervous system (CNS) neurons in situ may handle local swelling and shrinking perturbations so as to interfere minimally with the primary role of neurons, synaptic information processing. The strategy used for osmoreg-ulatory membrane adjustments may first come into play during ontogeny, when it could provide membrane tension sensitive membrane trafficking in arborized neu-rons subjected to morphogenetic forces. BACKGROUND Neuronal architecture—the carefully es-tablished arborizations of neurons, along with the minutiae of their neuron-neuron contacts—is key to information flow and information storage in the CNS. Though CNS neurons are protected from osmotic extremes, bouts of intense neural activity produce local swelling and shrinking influ-ences in the form of extracellular [K1] and intracellular osmolyte changes. Given the massively reticular architecture of the CNS, it is unsurprising that monitoring cell vol-ume and surface area dynamics in the CNS is dauntingly difficult. Compounding the difficulty, however, has been an unsettling disjunction between phenomena observed in volume-perturbed CNS cells isolated in culture and phenomena evident from CNS cells monitored collectively (i.e., in brain slice). Regulatory volume decrease—the set of cell-mediated processes by which swol-len cells reshrink towards their normal vol-ume in the continued presence of hypos-motic medium—is reported for neurons (Morán et al., 1997), glia (Morán et al., 1996) and endothelial cells (Hara et al., 1999) in culture, but to date, using a variety of methods, comparable regulatory volume decrease has not been detected in brain slic-es (e.g., Andrew et al., 1997, 1999)