Chronic L-lysine develops anti-pentylenetetrazol tolerance and reduces synaptic GABAergic sensitivity.
L-Lysine 10 mmol/kg given to mice for 1 to 10 days significantly increased clonic and tonic seizure latencies caused by 60 mg/kg pentylenetetrazol (PTZ). On day 1 the clonic and tonic seizure latencies were increased from 160.4 +/- 26.3 and 828.6 +/- 230.8 s to 286.1 +/- 103.3 and 982.3 +/- 98.6 s, respectively. Both clonic and tonic seizure latencies increased steadily with additional L-lysine treatment without significant change in survival rate. On day 10, the anticonvulsant effect reached its highest level with a block of tonic seizures and a survival rate of 100% without tolerance developing. Acute L-lysine treatment significantly increased the mean clonic latency from 85.8 +/- 5.24 to 128.2 +/- 9.0 s and the mean tonic seizure latency from 287.2 +/- 58.7 to 313.5 +/- 42.2 s with 80 mg/kg PTZ. On the day 10 of treatment, the anticonvulsant effect of L-lysine was highest, with a significant increase of 155 and 184% in clonic and tonic latencies over the control, respectively. After 15- and 20-day treatment, clonic and tonic seizures latencies and survival rate decreased, suggesting development of tolerance. Brain membranes from tolerant mice showed decreased enhancement by gamma-aminobutyric acid of specific [3H]flunitrazepam binding from 210 +/- 8 to 169 +/- 5% with EC50 values of 4.1 +/- 1.4 and 7.8 +/- 1.5 microM, respectively. Scatchard analysis of [3H] flunitrazepam binding showed no significant change of apparent binding affinity (KD) or binding density (Bmax) after chronic L-lysine exposure. L-Lysine enhanced the specific [35S]tert-butyl bicyclophosphorothionate (TBPS) binding in brain membranes dose dependently.(ABSTRACT TRUNCATED AT 250 WORDS)
Chang
Y F
YF
Department of Biochemistry, University of Maryland Dental School, Baltimore 21201-1586.
Wang
Y
Y
Cauley
R K
RK
Gao
X M
XM
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D018118:Chloride Channels; D002851:Chromatography, High Pressure Liquid; D004361:Drug Tolerance; D005445:Flunitrazepam / Q000378:metabolism; D007274:Injections, Intraperitoneal; D008239:Lysine / Q000378:metabolism / Q000494:pharmacology*; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects; D051379:Mice; D010433:Pentylenetetrazole / Q000037:antagonists & inhibitors* / Q000633:toxicity; D011963:Receptors, GABA-A / Q000187:drug effects* / Q000378:metabolism; D012640:Seizures / Q000139:chemically induced / Q000517:prevention & control; D013997:Time Factors
D018118:Chloride Channels; D008565:Membrane Proteins; D011963:Receptors, GABA-A; D005445:Flunitrazepam; D008239:Lysine; D010433:Pentylenetetrazole