Mechanisms of Regulation of Cerebral Microflow during Bicuculline-Induced Seizures in Anaesthetized Cats

Abstract

Summary: Before, during, and after bicuculline-induced seizures, changes in microflow, local tissue Po" and ex tracellular H+ and K + activities were contimiously re corded in the suprasylvian gyrus of the cat in parallel with electrical activity, Additionally, the patterns of microflow during seizures after blockade of the l3-adrenergic and cholinergic receptors and after phentolamine application were studied, With the onset of discharges, microflow increased at all sites, The maximum increase was ob served when the electrical activity was the strongest. During the period of alternating silent and non silent phases, microflow oscillated in parallel with functional activity, When the discharges ceased, microflow de creased to a new steady-state leveL Tissue hypoxia was It is well accepted from many experimental studies in animals and clinical studies in humans that epileptic seizures are accompanied by an in creased cerebral metabolism and an increased ce rebral blood flow, and that a tight coupling exists between cerebral metabolism and blood flow during seizures [for review see Kuschinsky and Wahl (1978) and Sokoloff (1978Sokoloff ( , 1981] . A good correla tion has also been found between the epileptic dis charges in the electroencephalogram and the in creased cortical blood flow during both generalized and focal seizures. As most of the studies of cere bral blood flow have been performed with methods that do not allow a continuous registration of blood flow, little information is available about the ki netics of cerebral blood flow during and after sei zures and especially in the silent phases of the elec trocorticogram (ECoG).

Brain Phenobarbital Uptake during Prolonged Status Epilepticus

“…The fall in brain ECF pH during status epilep ticus in the animals reported here (Fig. 2) is compa rable in degree and time course to measurements previously made in other species (Chapman et al, 1977;Leniger-Follert, 1984;Simon et al, 1985). The fall in pH is paralleled by an increase in brain lactate (Fig.…”

Interstitial Fluid Adenosine and Sagittal Sinus Blood Flow during Bicuculline-Seizures in Newborn Piglets

“…Also, the vasodilator action of adenosine was attenuated when pH in the vicinity of pial vessels was lowered to 6.8 (Kuschinsky et al, 1972;Wahl and Kus chinsky, 1977). During seizures, extracellular po tassium that rose to 10 mM temporally paralleled the increase in CBF and decrease in extracellular pH (Leniger-Follert, 1984).…”

“…With respect to oxy gen, brain tissue POz in adults is normally much lower than in neonates [e.g., between 1 and 70 mm Hg (mean, 24.5 mm Hg) in cats (Leniger-Follert, 1984)]. Because the piglet has a significantly lower arterial POz than eaes the cat, piglet brain tissue POz is also ex pected to be low.…”

“…It was found that at the onset of bicuculline sei zures the POz was higher than during the control periods (Leniger-Follert, 1984). These observations led the investigator to suggest that adenosine play s no role in regulation of CBF during bicuculline sei zures (Leniger-Follert, 1984).…”

“…8-fold (p < 0.05) during seizures associated with moderate sys temic hypotension and the low perfusate P02 (group 2, n Seizures induced by bicuculline increase CBF in neonatal and adult animals (Meldrum and Nilsson, 1976;Young et al , 1984;Clozel et al , 1985). Al though the precise mechanism for the increase in CBF during seizures remains unknown, the in crease has been partly attributed to cerebral vaso dilation mediated by local chemical factors (Heuser, 1978;Leniger-Follert, 1984). One of the proposed chemical factors linked to the increase in CBF during seizures is adenosine (Schrader et al , 1980;Winn et al , 1980).…”