The use of ultra-violet setting glue for microelectrode fabrication
Abstract The characteristics of glues which set in ultra-violet light are described with respect to their advantages for microelectrode assembly.
Presynaptic Actions and Dopamine in the Neostriatum
There are now very detailed anatomical descriptions of the structure of the neostriatum at the electronmicroscopic level (see e.g. Pasik et al., 1978) and it seems that axo-axonic synapses are rare. It should be said at the outset then, that the term presynaptic as used here does not necessarily imply any such anatomical substrate. The examples which we will discuss in detail employ very different methodologies and therefore need to be described separately in the sections below. There are three illustrations of interactions of neostriatal neurotransmitters which each warrant the use of the term “presynaptic”. In the case of the action of dopamine on cortico-striatal synapses (section 1) the action is thought to be presynaptic on physiological evidence. In the other two cases, the actions are identified in slices of striatal tissue which do not contain dopamine (DA) cell bodies. Since changes in DA release are observed they must be thought of as the results of actions on DA terminals in the slices, although perhaps not due to morphologically defined synapses on them.
To spritz or not to spritz: the doubtful value of aimless iontophoresis.
Publisher Summary This chapter discusses the different aspects of iontophoresis. The response of a neuron to a drug applied by iontophoresis can be determined by the changes in any parameter of cell activity. For cells with spontaneous electrical activity, changes in discharge pattern can be determined from interspike interval histograms and poststimulus time histograms can be used when test cells can be influenced by defined, isolated, monosynaptic inputs. In each case, accuracy of response measurements requires continuous detection of distinguishable action potentials of a constant spike height. With the recording barrel of a multibarrel electrode used in iontophoresis, extracellular spikes often have low signal to noise ratios and more than one cell can be recorded simultaneously. These signals can be improved electronically with gate or window discriminators provided that spike size remains constant. In iontophoretic tests, spike size can change by drift in the spatial relation between electrode and cell, by interaction between ejection or retention currents and the spike generating mechanisms of the cell, or when the drug to be tested has membrane anesthetizing properties. Noise levels are frequently increased during iontophoretic tests, especially when the drug solution has a high electrical impedance from low solubility or low ionization constants.