ABSTRACT
Vagus nerve stimulation (VNS) is an FDA approved treatment for drug-resistant epilepsy and depression. Recently, we demonstrated the capacity for repeatedly pairing sensory input with brief pulses of VNS to induce input specific reorganization in rat auditory cortex. This was subsequently used to reverse the pathological neural and perceptual correlates of hearing loss induced tinnitus. Despite its therapeutic potential, VNS mechanisms of action remain speculative. In this study, we report the acute effects of VNS on intra-cortical synchrony, excitability, and sensory processing in anesthetized rat auditory cortex. VNS significantly increased and decorrelated spontaneous multi-unit activity, and suppressed entrainment to repetitive noise burst stimulation at 6-8 Hz but not after application of the muscarinic antagonist scopolamine. Collectively, these experiments demonstrate the capacity for VNS to acutely influence cortical synchrony and excitability and strengthen the hypothesis that acetylcholine and muscarinic receptors are involved in VNS mechanisms of action. These results are discussed with respect to their possible implications for sensory processing, neural plasticity, and epilepsy.
Subject(s)
Auditory Cortex/physiology , Vagus Nerve/physiology , Acoustic Stimulation , Action Potentials , Animals , Auditory Cortex/drug effects , Electric Stimulation , Evoked Potentials, Auditory , Male , Muscarinic Agonists/pharmacology , Noise , Rats , Rats, Sprague-Dawley , Scopolamine/pharmacologyABSTRACT
Hemolysis was induced in erythrocyte suspensions by shearing between rotating metal disks 10 cm in diameter at 325 rev/min; stresses did not exceed 100 dynes/cm2. The role of proteins (gamma-globulin, G; albumin, A; fibrinogen, F) in the environment was tested in two ways. First, disks were precoated by exposure to protein solutions of physiologic concentration and then used to hemolyze the suspensions. Tests carried to 10(4) sec showed protective effects, relative to shearing with virgin disks, with a ranking G greater than A greater than F. Second, proteins were dissolved in the suspension media and hemolysis compared to the case without protein. Large suppression of hemolysis was found during storage (G approximately A greater than F) but only G offered significant protection against shear.
