SEIZURE-INDUCED C-FOS EXPRESSION IN RAT MEDULLA-OBLONGATA IS NOT DEPENDENT ON ASSOCIATED ELEVATION OF BLOOD-PRESSURE

This study was performed to determine whether c-fos immunoreactivity ( IR) induced in medulla oblongata by pentylenetetrazole seizures is a c onsequence of seizure-associated blood pressure elevation and activati on of baroreceptor afferent pathways, or occurs independently of hyper tension. Immunohistochemical study of sections of medulla oblongata re vealed that seizures are followed by induction of c-fos IR in nucleus tractus solitarius (NTS), dorsal motor nucleus of the vagus (DMN 10), and ventrolateral medulla (VLM), while there is negligible c-fos IR af ter saline sham injections. Seizures were associated with blood pressu re elevation peaking at 31+/-17% (+/-SD) above baseline. Experimental hypertension at a similar level induced by i.p. phenylephrine also res ulted in induction of c-fos IR in NTS. When seizures were preceded by antihypertensive treatment with the alpha-adrenergic antagonist, phent olamine, peak blood pressure tended to remain near the baseline level and lower than sham-injected controls. Normotensive seizures were asso ciated with c-fos IR in NTS, DMN 10, and VLM similar to the pattern fo llowing hypertensive seizures. Seizure-induced activation of c-fos IR occurred despite normal blood pressure, and thus can be attributed to a direct effect of the seizure, and not to an indirect effect mediated by hypertension.