Emphasis is placed on the complexity of homeostatic adaptations to reduced as well as intensified firing. Two kinds of adaptation are distinguished: (i) rapid recovery (within several hours) towards baseline levels despite sustained blockade of excitatory synaptic transmission, and click here (ii) the generation of essentially normal firing patterns in cultures assayed in control medium following development in the presence of excitatory receptor blockers. The former category of homeostatic responses is strongly dependent on the type of preparation, with isolated organotypic explants

showing greatly limited plasticity in comparison with co-cultures of matching contralateral pieces of cortical tissue. in such co-cultures, compensatory excitatory

drive manifests itself even when all three known types of ionotropic glutamate receptors are chronically blocked, and is then mediated by (muscarinic) cholinergic mechanisms which normally do not contribute measurably to spontaneous activity.

The rapid return of high levels of spontaneous firing during sustained selective glutamatergic receptor blockade appears see more to protect neuronal cultures treated in this way from becoming hyperexcitable. in particular, quasi-epileptiform paroxysmal bursting upon return to control medium, such as appears in preparations where bioelectric RVX-208 activity has been totally suppressed during network formation, fails to appear in chronically receptor blocked cultures. On the contrary, desensitization of blocked glutamate receptors, as a physiological compensation for the up-regulation of non-blocked receptors, could be demonstrated for both the AMPA and the NMDA glutamate receptor sub-types. This wide range of homeostatic responses underscores the importance of spontaneous neuronal

discharges for setting and maintaining an optimal balance between excitatory and inhibitory mechanisms in developing neocortical networks. (c) 2008 Elsevier Ltd. All rights reserved.”
“Among well-nourished populations, eating beyond homeostatic needs when presented with caloric-dense palatable food evidences the assertion that an increasing proportion of consumption is driven by pleasure, not just by the need for calories. This presents a major health crisis because the affective component of foods constitutes a behavioral risk factor that promotes over consumption [Sorensen, L.B,, Moller, P., Flint,A., Martens, M., Raben,A., 2003. Effect of sensory perception of foods on appetite and food intake: a review of studies on humans. Int. J. Obes. Relat. Metab. Disord. 27, 1152-1166; Yeomans, M.R., Blundell, J.E., Leshem, M., 2004. Palatability: response to nutritional need or need-free stimulation of appetite? Br. J. Nutr.