Comparison between fluorimetric and radiochemical assays of iontophoretically released noradrenaline from a seven-barreled micropipette

Improved techniques for examining rapid dopamine signaling with iontophoresis

Dopamine is a neurotransmitter that is utilized in brain circuits associated with reward processing and motor activity. Advances in microelectrode techniques and cyclic voltammetry have enabled its extracellular concentration fluctuations to be examined on a subsecond time scale in the brain of anesthetized and freely moving animals. The microelectrodes can be attached to micropipettes that allow local drug delivery at the site of measurement. Drugs that inhibit dopamine uptake or its autoreceptors can be evaluated while only affecting the brain region directly adjacent to the electrode. The drugs are ejected by iontophoresis in which an electrical current forces the movement of molecules by a combination of electrical migration and electroosmosis. Using electroactive tracer molecules, the amount ejected can be measured with cyclic voltammetry. In this review we will give an introduction to the basic principles of iontophoresis, including a historical account on the development of iontophoresis. It will also include an overview of the use of iontophoresis to study neurotransmission of dopamine in the rat brain. It will close by summarizing the advantages of iontophoresis and how the development of quantitative iontophoresis will facilitate future studies.

Iontophoresis in dermatology. A review

Iontophoresis, the process of increasing the penetration of drugs into surface tissues by the application of an electric current, has been applied to a great many disease conditions over its 200-year history. Although its greatest success has been in the treatment of hyperhidrosis, it is steadily finding new applications. Many aspects of the mechanisms of iontophoresis have yet to be studied before the technic is both fully understood and maximally utilized. In this article we review the literature on iontophoresis as it pertains to dermatology, including the basic principles, engineering aspects.

Inhibition from locus coeruleus of caudate neurons activated by nigral stimulation

Electrophysiological studies were performed to determine if the locus coeruleus (LC) plays a role in regulating activity of caudate nucleus (CN) neurons. Cats were anesthetized with alpha-chloralose and when conditioning stimuli were applied to the LC, preceding the test stimulus, there was a significant inhibition of spike generation in 33 out of 93 CN neurons transsynaptically activated by test stimulus to the pars compacta of the substantia nigra (SN). An inhibition of spike generation with LC conditioning stimulation and iontophoretic application of noradrenaline was obtained in 9 out of the same 23 CN neurons and 8 neurons remained unaffected with either treatment. In contrast to these neurons, LC conditioning stimulation did not affect the spontaneous firing and spike generation of CN neurons antidromically excited by SN stimulation. Spike firing of CN neurons transsynaptically activated by motor cortex stimulation remained unaffected with LC conditioning stimulation. These results suggest that noradrenaline derived from the LC produced an inhibition of spike generation in about one-third of CN neurons tested and transsynaptically activated by SN stimulation.