L-pGlu-(2-propyl)-L-His-L-ProNH₂ attenuates 4-aminopyridine-induced epileptiform activity and sodium current: a possible action of new thyrotropin-releasing hormone analog for its anticonvulsant potential.
L-PGlu-(2-propyl)-L-His-L-ProNH₂ (NP-647) is a CNS active thyrotropin-releasing hormone (TRH) analog with potential application in various CNS disorders including seizures. In the present study, mechanism of action for protective effect of NP-647 was explored by studying role of NP-647 on epileptiform activity and sodium channels by using patch-clamp methods. Epileptiform activity was induced in subicular pyramidal neurons of hippocampal slice of rat by perfusing 4-aminopyridine (4-AP) containing Mg⁺²-free normal artificial cerebrospinal fluid (nACSF). Increase in mean firing frequency was observed after perfusion of 4-AP and zero Mg⁺² (2.10±0.47 Hz) as compared with nACSF (0.12±0.08 Hz). A significant decrease in mean firing frequency (0.61±0.22 Hz), mean frequency of epileptiform events (0.03±0.02 Hz vs. 0.22±0.05 Hz of 4-AP+0 Mg), and average number of action potentials in paroxysmal depolarization shift-burst (2.54±1.21 Hz vs. 8.16±0.88 Hz of 4-AP+0 Mg) was observed. A significant reduction in peak dV/dt (246±19 mV ms⁻¹ vs. 297±18 mV ms⁻¹ of 4-AP+0 Mg) and increase (1.332±0.018 ms vs. 1.292±0.019 ms of 4-AP+0 Mg) in time required to reach maximum depolarization were observed indicating role of sodium channels. Concentration-dependent depression of sodium current was observed after exposure to dorsal root ganglion neurons to NP-647. NP-647 at different concentrations (1, 3, and 10 μM) depressed sodium current (15±0.5%, 50±2.6%, and 75±0.7%, respectively). However, NP-647 did not show change in the peak sodium current in CNa18 cells. Results of present study demonstrated potential of NP-647 in the inhibition of epileptiform activity by inhibiting sodium channels indirectly.
Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560012, India.
N
N
Sah
S K
SK
Rajput
J N
JN
Singh
C L
CL
Meena
R
R
Jain
S K
SK
Sikdar
S S
SS
Sharma
D015761:4-Aminopyridine / Q000633:toxicity; D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D003292:Convulsants / Q000633:toxicity; D004827:Epilepsy / Q000378:metabolism / Q000503:physiopathology; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D017208:Rats, Wistar; D012640:Seizures / Q000378:metabolism / Q000503:physiopathology; D015222:Sodium Channels / Q000187:drug effects / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology
D000927:Anticonvulsants; D003292:Convulsants; D015222:Sodium Channels; C539979:pyroglutamyl-(2-propyl)histidyl-prolinamide; D013973:Thyrotropin-Releasing Hormone; D015761:4-Aminopyridine