Subfractionation of ficoll gradient purified synaptosomes: GABA uptake by the subfractions.

The classical synaptosomes preparation purified on discontinuous Ficoll gradient has been sufractionated into three further subfractions by introducing more Ficoll density layers. Among the three subfractions, the lightest one was the one which was more difficult to obtain in reproducible amounts and was only partially characterized in terms of labelled GABA uptake. The heaviest one most probably is largely made up of partially damaged nerve endings. The central one was the most reproducible in terms of yield and labelled GABA uptake and actually was the one we studied more thoroughly in terms of morphology, labelled GABA uptake and its pharmacology. A comparison has been made with the classical "total" purified synaptosomes fraction. An interesting result of these experiments is a paradoxical effect of the glial uptake inhibitor beta-alanine. This substance appears to favor, in both "total" and "central" fraction synaptosomes, a redistribution of taken up GABA from contaminating glia to actual nerve endings.

GABA uptake by rabbit restiform body homogenates.

Restiform body (inferior cerebellar peduncle) preparations were obtained from rabbit brain stem slices and homogenized. When challenged with labelled GABA, these homogenates took it up briskly. We have characterized pharmacologically this uptake which resulted almost equally neuronal and glial. The neuronal component of the GABA uptake might be due to the adjacent cochlear nuclei coming along in the preparations, whereas the glial component probably belongs to the restiform body proper. Another possibility is that actually both components are due to the myelinated fibers and glia which make up the restiform body.

Visualization of nimodipine (NIM) binding sites of rat brain by means of a NIM-colloidal gold complex (1-2).

It is described a new method to visualize the binding sites of the Ca(2+)-antagonist nimodipine (NIM) on brain cryostatic sections. NIM was bridged to colloidal gold sols by a suitable amphophilic detergent, and used according to autoradiographic procedures. A detailed mappage of vascular and neuronal NIM binding sites was allowed by silver-intensification of the NIM-gold complex bound to the nervous tissue. Selective distribution patterns were visualized in the main cerebral and cerebellar areas, suggesting that the drug potentially may act on multiple, different targets in the CNS.

Analogic delay lines for electrophysiological signals: practical approaches in CNS spike-activity analysis.

In extracellular microelectrode recordings of single PT-neurons, the time-shift of the signals by means of two different analogic delay lines allowed both the morphology of the spontaneous spikes and the related periods of antidromic unresponsiveness to be carefully evaluated. It has been shown that the limitations of the FM-type recorder delay technique can be avoided employing an integrated shift-register delay line for analogic signal processing.

Ortho-antidromic latency fitting and identification of antidromically activated CNS long-axoned neurones.

The intrinsic errors of the collision test were evaluated in extracellular recordings of cat's pyramidal tract (PT)-units. A modified collision technique by means of paired and suitably timed PT-stimuli allowed the demonstration of the ortho-antidromic latency fitting. This method could represent an important counterproof to the true antidromic activation of CNS long-aconed neurons.