Electroshock- and pentylenetetrazol-induced seizures in genetically epilepsy-prone rats (GEPRs): differences in threshold and pattern.
Using facial and forelimb (F&F) clonus (a proposed forebrain marker) and running-bouncing (R/B) clonus and tonus (proposed brain-stem markers), the responsiveness of forebrain and brain-stem to electroshock or pentylenetetrazol seizures was assessed in GEPRs. The most striking finding was the failure of GEPR-9s to display F&F clonus in response to transcorneal electroshock at any stimulus intensity. Indeed, GEPR-9s displayed only R/B clonus or tonus indicative of brain-stem seizure discharge. GEPR-3s and normal rats, on the other hand, displayed F&F clonus in response to the least effective electroshock stimulus, and R/B clonus and tonus at higher stimulus intensities. After treatment with phenytoin (50 mg/kg) to inhibit the tonic seizure, the least effective electroshock stimulus also produced F&F clonus in GEPR-9s. These findings suggest that the threshold for triggering brain-stem seizure discharge by electroshock is lower than that for triggering forebrain seizure discharge in GEPR-9s, whereas the reverse relationship is true in normal rats and GEPR-3s. The rank ordering of the electroshock thresholds was: normals greater than GEPR-3s greater than GEPR-9s. Both GEPR-3s and GEPR-9s were found to be hyper-responsive to pentylenetetrazol as evidenced by shorter latency for the tonic seizure and a greater seizure severity than normal rats. The rank ordering of seizure severity in response to pentylenetetrazol was: GEPR-9 greater than GEPR-3 greater than normal rats.
Browning
R A
RA
Department of Physiology, Southern Illinois University School of Medicine, Carbondale 62901-6512.
Wang
C
C
Lanker
M L
ML
Jobe
P C
PC
D000818:Animals; D000927:Anticonvulsants / Q000627:therapeutic use; D004827:Epilepsy / Q000139:chemically induced* / Q000188:drug therapy / Q000503:physiopathology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology*; D007696:Kindling, Neurologic; D008297:Male; D010433:Pentylenetetrazole; D010672:Phenytoin / Q000627:therapeutic use*; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time
D000927:Anticonvulsants; D010672:Phenytoin; D010433:Pentylenetetrazole