1. Redistribution of transmitter amino acids in rat hippocampus and cerebellum during seizures induced by L-allylglycine and bicuculline: an immunocytochemical study with antisera against conjugated GABA, glutamate and aspartate
B S Meldrum, J Storm-Mathisen, O P Ottersen, J H Swan Neuroscience . 1987 Jul;22(1):17-27. doi: 10.1016/0306-4522(87)90194-1.
The effects of the convulsants L-allylglycine and bicuculline on the distribution of gamma-amino-butyric acid (GABA), glutamate and aspartate in rat brains were assessed immunocytochemically, using antisera raised against glutaraldehyde-protein conjugates of the respective amino acids. In accord with previous biochemical studies of GABA content, L-allylglycine treatment was followed by a decreased immunoreactivity for GABA in the hippocampus and cerebellum, whereas treatment with bicuculline led to an increased immunoreactivity in the hippocampus, but not in the cerebellum. Different cells and zones were affected differentially. With both convulsants the hippocampus showed the most pronounced changes in the neuropil of the pyramidal and granular cell layers. L-Allylglycine treatment led to a substantial decrease in the concentration of detectable GABA-immunoreactive bouton-like dots in the stratum oriens, radiatum and lacunosum-moleculare and in the deep hilar region, but did not produce statistically significant changes in this parameter in the outer and intermediate zones of the dentate molecular layer. In the cerebellum, the decrease in GABA immunoreactivity after L-allylglycine treatment was less in the basket cell terminals than in other GABA-containing elements. Neither convulsant altered the average staining intensity for aspartate or glutamate in the two regions studied, but L-allylglycine reduced the level of aspartate-like immunoreactivity in hippocampal hilar cells. All the changes described were evident after 20 min of seizure activity and were qualitatively similar after 60 min of seizure (animals paralysed and ventilated). Our results indicate that L-allylglycine or bicuculline given intravenously exerts specific effects on cerebral amino acid metabolism. The nature and magnitude of these effects show inter-regional variations and also differ among cellular compartments within each region. Amino acid immunocytochemistry may prove to be a valuable tool for the investigation of metabolic changes associated with epileptic seizures and should be particularly useful in regions showing heterogeneous changes that would tend to cancel each other in biochemical analyses.
2. Strychnine and L-allylglycine but not bicuculline and picrotoxin induce transsynaptic degeneration following transection of the inferior alveolar nerve in adult rats
A Sakai, T Sugimoto, J Okubo, M Takemura Brain Res . 1985 Aug 26;341(2):393-8. doi: 10.1016/0006-8993(85)91082-0.
The effects of the convulsants strychnine, bicuculline, picrotoxin and L-allylglycine on the transsynaptic destruction of medullary dorsal horn neurons were examined following transection of the inferior alveolar nerve in adult rats. Strychnine and L-allylglycine enhanced the transsynaptic effect of nerve transection and caused degeneration of many dorsal horn neurons, while bicuculline and picrotoxin did not. The removal of glycinergic and GABAergic postsynaptic inhibition appears to enhance the transsynaptic destructive activity which follows the peripheral nerve transection.
3. Intracellular calcium accumulation in rat hippocampus during seizures induced by bicuculline or L-allylglycine
B S Meldrum, T Griffiths, M C Evans Neuroscience . 1983 Oct;10(2):385-95. doi: 10.1016/0306-4522(83)90141-0.
Using electron microscopy and the combined oxalate-pyroantimonate technique, free calcium ions were located in the hippocampus of control rats and of those that had undergone status epilepticus induced by L-allylglycine or bicuculline. The validity of this technique was established by the use of the calcium chelating agent ethylene glycol bis(beta-aminoethyl ether), N,N'-tetra-acetic acid and by an X-ray microanalytical technique. In control material, calcium deposits were visible in synaptic vesicles and multivesicular bodies, in parts of the Golgi apparatus, mitochondria, lysosomes, and in glial and neuronal nuclei. Following 2 h of status epilepticus, cellular pathology included astrocytic swelling, and dark cell degeneration of pyramidal neurons. This was accompanied by a marked increase in the amount of calcium pyroantimonate deposits, particularly in swollen and disrupted mitochondria of CA1 and CA3 basal dendrites, and in selected neuronal cell bodies in the CA1 and CA3-4 regions. We propose that enhanced calcium entry into neurons and consequent overloading of the capacity of mitochondria for calcium sequestration is part of the cytotoxic mechanism leading to selective neuronal loss in the hippocampus in status epilepticus.
