A possible role for spinal noradrenaline in the mechanisms of 6-hydroxydopamine against pentylenetetrazol induced convulsions in rats

Alterations of lidocaine and pentylenetetrazol-induced convulsions by manipulation of brain monoamines

The thresholds for pentylenetetrazol and lidocaine-induced clonic convulsions were significantly influenced by manipulation of brain biogenic amines. Pretreatment with inhibitors of monoamine synthesis, alpha-methyl-p-tyrosine and p-chlorophenylalanine, caused significant decreases in brain monoamine contents and pentylenetetrazol seizure threshold, while the threshold for lidocaine-induced convulsions was significantly increased by either treatment. Moreover, the inhibitor of dopamine-beta-hydroxylase, disulfiram, caused significant decrease in brain noradrenaline (NA) and significant increase in brain dopamine (DA) contents. The threshold for pentylenetetrazol-induced convulsions was decreased by treatment with disulfiram, while that of lidocaine was increased by the same treatment. Furthermore, treatment with L-dihydroxyphenylalanine (L-DOPA) caused significant increase in brain DA contents, while 5-hydroxytryptophan (5-HTP) treatment caused significant increase in brain 5-hydroxytryptamine (5-HT) contents, but the thresholds for lidocaine and pentylenetetrazol-induced convulsions were not influenced by either treatment. These results may suggest that the brain monoaminergic systems, different from their ability to inhibit control of pentylenetetrazol seizures, act to potentiate lidocaine-induced convulsions.

Anticonvulsant activity of di-n-propylacetate and brain monoamine metabolism in the rat

1. Sodium di-n-propylacetate (DPA) treatment induced significant increases in brain contents of gamma-aminobutyric acid (GABA), 5-hydroxyindoleacetic acid (5-HIAA) and homovanillic acid (HVA). Furthermore, the threshold for pentylenetetrazol (PTZ) clonic convulsions was also increased in response to DPA administration. 2. Pretreatment with inhibitors of monoamine synthesis alpha-methyl-p-tyrosine (AMPT) and p-chlorophenylalanine (PCPA) did not alter the anticonvulsant activity of DPA, but when given alone, both AMPT and PCPA caused significant decreases in brain monoamine contents and PTZ threshold seizures. 3. Experiments using probenecid suggest that the increases in 5-HIAA and HVA seen after DPA treatment could have resulted from inhibition of their active transport out of the brain. These data indicate that the anticonvulsant action of DPA is not dependent on changes in monoamine metabolism in the brain.