Involvement of proprioceptive feedback in brainstem-triggered convulsions.
OBJECTIVE
In rodents, specific motor components of generalized convulsive seizures depend on two distinct anatomic substrates: (a) forebrain networks are responsible for facial and forelimb clonus with or without rearing and falling; and (b) brainstem networks are responsible for running-bouncing fits and tonic convulsions. To investigate the requirement of proprioceptive inputs in the generation of these two different types of seizures, we compared the effects of neuromuscular blockade by D-tubocurarine on the EEG expression of brainstem- and forebrain-triggered seizures.


METHODS
Unilateral electrical stimulations were applied for 50 consecutive days in freely moving male adult rats through a bipolar electrode aimed at the dorsal hippocampus (n = 5), the occipital cortex (n = 4), the inferior colliculus (n = 6), or the midbrain reticular formation (n = 6). Two days after the last stimulation, rats were paralyzed with d-tubocurarine and stimulated in the same way.


RESULTS
In brainstem structures, the first electrical stimulation induced tonic seizures concomitant with low-voltage cortical activity; repetition of daily stimulations progressively induced tonic-clonic seizures associated with high-amplitude cortical spike-wave discharges. After immobilization by d-tubocurarine, brainstem stimulations failed to induce any EEG paroxysm. In forebrain structures, repeated electrical stimulations produced a classic kindling with progressive occurrence of clonic seizures associated with large cortical discharges; d-tubocurarine left unchanged the EEG pattern of these latter seizures.


CONCLUSIONS
These data suggest that proprioceptive reafferentation resulting from movement is necessary for the generation of self-sustained brainstem seizures but is not implicated in the elaboration of forebrain seizures.
Maton
B
B
INSERM U 398, Faculté de Médecine, Hôpitaux Universitaires, Strasbourg, France.
Vergnes
M
M
Hirsch
E
E
Marescaux
C
C
D000818:Animals; D001933:Brain Stem / Q000503:physiopathology*; D004558:Electric Stimulation; D004569:Electroencephalography; D005246:Feedback / Q000502:physiology*; D007103:Immobilization; D007696:Kindling, Neurologic / Q000502:physiology*; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D011434:Proprioception / Q000502:physiology*; D016548:Prosencephalon / Q000503:physiopathology; D051381:Rats; D012640:Seizures / Q000209:etiology* / Q000503:physiopathology; D014403:Tubocurarine / Q000494:pharmacology
D014403:Tubocurarine