Involvement of the orbitofrontal cortical IL-1β mechanisms in the central homeostatic control

The complex system of chemosensory neurons of the glucose-monitoring neural network (GMNN)–by integrating various feeding-associated exogenous sensory cues with endogenous humoral signals and with perceptual as well as motivational information–possesses multiple functional attributes in the homeostatic control. It is well known that pathophysiological processes (infections, tumors, injuries, etc.) alter defense and adaptive reactions of these control mechanisms. The so-called cytokines–and one of their major representatives the interleukin-1β (IL-1β) itself–are suggested to interact with the CNS and to play essential role in these above reactions. To elucidate the involvement of orbitofrontal cortical glucose-monitoring (GM) neurons in these functions, complex microelectrophysiological–neurochemical as well as behavioral–biochemical experiments were performed. The single neuron activity recording study demonstrated that high proportion of GM neurons in the rat orbitofrontal cortex (OBF) were shown to change their firing rate in response to the microelectrophoretically administered IL-1β. We also proved that IL-1β microinjection into the rat OBF resulted in the development of complex feeding and metabolic disturbances. Our findings, therefore, confirm that neocortically organized IL-1β-mediated adaptive reactions through orbitofrontal cortical constituents of the GMNN play important roles in the biologically adaptive central homeostatic control.