[Running fit and generalized tonic-clonic seizure are differently controlled by different subtype receptors in the brainstem].
Rats neonatally treated with 0.02% propylthiouracil (PTU) through mother's milk showed a high incidence of audiogenic seizures after maturation. These audiogenic seizures were differently modified by MK-801 and NBQX; while intraperitoneal MK-801 equally inhibited running fit (RF) and generalized tonic-clonic seizure (GTCS), NBQX administered into cisterna ambiens significantly inhibited RF but not GTCS. The possible involvement of glutamate receptors in the inferior colliculus was further investigated using naive Sprague-Dawley rats injected with NMDA, AMPA or cyclothiazide, known as an inhibitor of desensitization of AMPA action. All drugs tested successfully induced RF followed by GTCS, resembling audiogenic seizures in PTU-treated rats. However, sound stimulation could augment AMPA-induced, but not NMDA-induced GTCS. Systemic administration with MK-801 potently blocked GTCS induced by AMPA/cyclothiazide, but the same drug failed to block RF after intracisternal injection with AMPA/cyclothiazide. Furthermore, intracisternal administration with NBQX significantly inhibited only RF induced by AMPA/cyclothiazide. The present study suggests that: 1) glutamate receptors in the brainstem, possible in the inferior colliculus, play a crucial role in audiogenic seizures, namely the initiation of RF and propagation into GTCS; and 2) the initiation mechanism is regulated by both NMDA and AMPA receptors, whereas propagation is mainly controlled by NMDA receptors.
Yasuda
S
S
Department of Psychiatry, Shiga University of Medical Science, Otsu, Japan.
Ishida
N
N
Higashiyama
A
A
Kato
N
N
D000161:Acoustic Stimulation; D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology; D001581:Benzothiadiazines / Q000494:pharmacology; D001933:Brain Stem / Q000502:physiology*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004830:Epilepsy, Tonic-Clonic / Q000503:physiopathology; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D007245:Inferior Colliculi / Q000187:drug effects / Q000503:physiopathology*; D016202:N-Methylaspartate / Q000494:pharmacology; D018696:Neuroprotective Agents / Q000494:pharmacology; D011441:Propylthiouracil; D011810:Quinoxalines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018091:Receptors, AMPA / Q000502:physiology; D017470:Receptors, Glutamate / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D012640:Seizures / Q000139:chemically induced / Q000503:physiopathology*; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D000927:Anticonvulsants; D001581:Benzothiadiazines; D018690:Excitatory Amino Acid Agonists; D018696:Neuroprotective Agents; D011810:Quinoxalines; D018091:Receptors, AMPA; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; C062865:2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline; D016202:N-Methylaspartate; D016291:Dizocilpine Maleate; D011441:Propylthiouracil; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; C004639:cyclothiazide