Affiliation:
1. Department of Neuroscience, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
2. Department of Physiology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA
Abstract
Intrinsic optical changes that follow infundibular stalk stimulation of the neurointermediate lobe of the mouse pituitary gland exhibit three different phases that reflect three distinct physiological events. The first (E-wave) is the rapid light-scattering increase that is associated with a nerve terminal volume increase (mechanical spike), and that accompanies excitation of the neurohypophysial terminals by the invading action potential; the second (S-wave) is the slower light-scattering decrease that is tightly correlated with the secretion of the peptide hormones oxytocin and arginine vasopressin, and the third is the long-duration response (R-wave) that reflects cell volume changes in the pars intermedia. We have studied the E-wave and the S-wave in earlier publications. The R-wave, considered here, is sensitive to chloride replacement as well as to blockade of chloride channels. By blocking GABAA receptors (which are ligand-gated chloride channels) with pharmacological agents, and by applying GABA directly into the bathing solution, or evoking its release from GABAergic inputs, we have demonstrated that this long-duration optical response is sensitive to chloride movements and reflects GABA-induced changes in the intrinsic optical properties of the pars intermedia. The full time-course of this optical response takes minutes and, therefore, has to embody some other process (or processes) related to the restoration of resting physiological chloride concentrations, following the opening and closing of GABAA-receptor channels. Here we demonstrate that the shape of the R-wave, the long-lasting light-scattering signal, is indeed affected by the activity of GAT1, one of the sodium- and chloride-dependent GABA transporters.
Publisher
World Scientific Pub Co Pte Lt
Subject
Biomedical Engineering,Atomic and Molecular Physics, and Optics,Medicine (miscellaneous),Electronic, Optical and Magnetic Materials