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In addition to the well-characterized direct and indirect projection neurons there are four major interneuron types in the striatum. Three contain GABA and either parvalbumin, calretinin or NOS/NPY/somatostatin. The fourth is cholinergic. It might be assumed that dissociated cell cultures of striatum (typically from embryonic day E18.5 in rat and E14.5 for mouse) contain each of these neuronal types. However, in dissociated rat striatal (caudate/putamen, CPu) cultures arguably the most important interneuron, the giant aspiny cholinergic neuron, is not present. When dissociated striatal neurons from E14.5 Sprague–Dawley rats were mixed with those from E18.5 rats, combined cultures from these two gestational periods yielded surviving cholinergic interneurons and representative populations of the other interneuron types at 5 weeks in vitro. Neurons from E12.5 CD-1 mice were combined with CPu neurons from E14.5 mice and the characteristics of striatal interneurons after 5 weeks in vitro were determined. All four major classes of interneurons were identified in these cultures as well as rare tyrosine hydroxylase positive interneurons. However, E14.5 mouse CPu cultures contained relatively few cholinergic interneurons rather than the nearly total absence seen in the rat. A later dissection day (E16.5) was required to obtain mouse CPu cultures totally lacking the cholinergic interneuron. We show that these cultures generated from two gestational age cells have much more nearly normal proportions of interneurons than the more common organotypic cultures of striatum. Interneurons are generated from both ages of embryos except for the cholinergic interneurons that originate from the medial ganglionic eminence of younger embryos. Study of these cultures should more accurately reflect neuronal processing as it occurs in the striatum in vivo. Furthermore, these results reveal a procedure for parallel culture of striatum and cholinergic depleted striatum that can be used to examine the function of the cholinergic interneuron in striatal networks. [ABSTRACT FROM AUTHOR]

The containment lifetime of the cosmic radiation is a crucial parameter in the investigation of the cosmic-ray origin and plays an important role in the dynamics of the Galaxy. The separation of the cosmic-ray Be isotopes achieved by two satellite experiments is considered in this paper, and from the measured isotopic ratio between the radioactive Be (half-life = 1.5 × 10 yr) and the stable Be, it is deduced that the cosmic rays propagate through matter with an average density of 0.24 ± 0.07 atoms cm, lower than the traditionally quoted average density in the galactic disk of 1 atom cm. This paper reviews the implications of this result for the cosmic-ray age mainly in the context of two models of confinement and propagation: the homogeneous model, normally identified with confinement to the galactic gaseous disk, and a diffusion model in which the cosmic rays extend into a galactic halo. The propagation calculations use: The satellite results and their implications are compared with the information on the cosmic-ray age derived from other cosmic-ray radioactive nuclei and the measured differential energy spectrum of high-energy electrons. It is a major conclusion of this paper that in a homogeneous model the cosmic-ray age is 15(+7, -4) million years, i.e., about a factor 4 longer than early estimates based on the abundances of the light nuclei Li, Be, and B and a nominal interstellar density of 1 atom cm . The lifetime is even longer when the satellite results are applied to a diffusion halo model. The deduced traversed matter density, together with other astrophysical considerations, suggest the population of a galactic halo by the cosmic rays. [ABSTRACT FROM AUTHOR]

Extracellular single unit recordings were obtained from dopamine cells in the substantia nigra pars compacta during forced locomotion on a circular turntable treadmill. Stainless steel wire electrodes, 18 μm diameter, insulated with Parylene C were used. During the entire recording session the rat was in the treadmill apparatus. The device was stopped while a cell was being sought. A cell was identified as dopaminergic by a frequency of 3 to 10 Hz and a biphasic or triphasic action potential of greater than 2 ms in duration. An attempt was made to record from cells under the following conditions: animal at rest, animal turning in one direction, at rest again, turning in the opposite direction and finally, at rest. If the cell was still firing after these recordings, haloperidol was injected i.p. to see that the presumed dopamine cell increased its firing rate. A cell was held for all the observations in 4 animals. In an additional 10 rats, recordings were made before, during and after movement in one direction. Three animals were recorded only before and during movement. In 6 of the total of 17 animals haloperidol was administered. Results showed that firing patterns of cells in awake animals were similar to those reported from dopamine cells of anesthetized rats. During either contralateral or ipsilateral turning the firing frequency and burst activity significantly increased. These results indicate that the activity of dopamine cells in substantia nigra is increased bilaterally during circling. [ABSTRACT FROM AUTHOR]

Parahorizontal slices of the neostriatum from young adult male rats were maintained at the fluid interface of a perfusion chamber. Intracellular recordings were made with potassium acetate filled micropipettes. The mean resting membrane potential of the neurones was -84 mV and all produced action potentials which overshot 0 mV. All the cells were silent at resting membrane potentials and only fired in response to depolarizing pulses delivered through the intracellular electrode. When long pulses were applied, the firing rate within the train of action potentials evoked was slower at the end of the pulse. In a very few cells at resting membrane potential, but in all cells depolarised from a holding potential of-65 mV, the resulting train of action potentials was followed by a slow hyperpolarizing potential. The potential observed was smaller in amplitude than the afterhyperpolarization seen in hippocampal pyramidal cells in vitro, but its voltage sensitivity was similar. Iontophoresis of dopamine (DA) close to the recording pipette resulted in two distinct actions. Firstly, DA reduced the number of action potentials following a short pulse, by increasing the threshold for spike initiation. Secondly, it also inhibited the hyperpolarizing potential which followed trains of action potentials even when allowance was made for the increased firing threshold. The inhibition of this hyperpolarization was accompanied by an increase in the number of spikes per pulse. Whether these two actions of DA are mediated by a single receptor/ membrane action is unclear. Nevertheless, they may help to reconcile the contradictory literature regarding the action of DA upon extracellular responses in striatal cells. When threshold effects are studied the action of DA will be inhibitory. On the contrary an excitation will be seen when trains of action potentials follow activation of the cells, since the reduction in the afterhyperpolarization by dopamine will result in decreased accommodation and more spikes per depolarizing stimulus. [ABSTRACT FROM AUTHOR]