Activation of cerebral cortex during acoustic challenge or acute foot-shock in freely moving, nontethered rats.

Most brain mapping techniques require immobilization of the subject, which extinguishes all but the simplest behaviors. We applied in freely moving rats an implantable microbolus infusion pump (MIP) which can be triggered by remote activation for the injection of the cerebral blood flow tracer [(14)C]iodoantipyrine during behavioral activation. Consistent with previous electrophysiological, metabolic and brain anatomic studies, CBF-related tissue radioactivity (CBF-TR) increased in acoustic cortex during a 1000 Hz/8000 Hz alternating tone. In response to an acute foot-shock, CBF-TR increased in visual cortex, parietal association cortex, and extended into primary motor cortex, and primary somatosensory cortex mapping the trunk. These results support the utility of implantable pumps as adjunct tools for studying cerebral activation during behavioral challenges in nontethered, nonrestrained animals.