Brain research
-
We investigated the effect of methylprednisolone on pathophysiological alterations in experimental pneumococcal meningitis. Untreated rats injected with pneumococcal cell wall components after hydrolization with M1 muramidase (PCW-M) developed an increase of regional cerebral blood flow (rCBF; 165.0 +/- 12.8%, baseline 100%, mean +/- S. E. ⋯ However, methylprednisolone did not inhibit the increase of rCBF (163.5 +/- 13.7% and 160.9 +/- 6.8%, resp.), whereas dexamethasone significantly attenuated microvascular changes. Hypercapnia-induced reactivity of cerebral vessels tested 8 h after i.c. injection was preserved in all groups. In conclusion, we found that methylprednisolone significantly attenuated the increase of brain water content, ICP and CSF WBC count, but had no effect on microvascular changes during the early phase of experimental pneumococcal meningitis.
-
Synaptic inhibition in rat spinal cord is mediated by the amino acids gamma-aminobutyric acid (GABA) and glycine. Most spinal cord neurons respond to both neurotransmitters, suggesting co-expression of GABAA- and strychnine-sensitive glycine-receptors in individual cells. While the distribution of glycine-receptors has been extensively characterized, much less is known about the cellular localization of GABAA-receptors in spinal cord neurons. ⋯ Double-immunofluorescence staining showed that most GABAA-receptor-positive cells in layers III-VIII and X also exhibited a prominent glycine-receptor immunoreactivity. Both types of receptors had very similar distribution patterns in the cell membrane and were frequently co-localized in sites apposed to GABAergic axon terminals. These results indicate that GABAA- and glycine-receptors may co-exist within single postsynaptic densities, suggesting a possible synergism in the action of GABA and glycine in spinal cord neurons.
-
Comparative Study
Rostral-caudal differences in effects of nucleus accumbens amphetamine on VTA ICSS.
The effects of amphetamine along the rostrocaudal axis of the nucleus accumbens (NAcc) on ventral tegmental area (VTA) intracranial self-stimulation (ICSS) were studied. Eighteen rats were trained to lever press for ICSS in the VTA. Rate-frequency functions were determined by logarithmically decreasing the frequency of cathodal pulses in a stimulation train from a value that induced maximal responding to one that induced no responding (thresholds). ⋯ Further analyses revealed a significant positive correlation (r13 = 0.51, P < 0.05) between the site of injection along the rostrocaudal axis of the NAcc and the size of the amphetamine-produced potentiation of VTA stimulation reward. Others have reported topographical differences, including dopamine terminal density and D1 receptor density, in the NAcc. The present results indicate that these anatomical and neurochemical differences appear to be correlated with behavioural differences.