Effects of pentobarbital on entorhinal tetanic responses and the progression of afterdischarges during the early course of amygdala kindling in rats.
We investigated the relationship between the progress of afterdischarges (AD) and the development of facilitated entorhinal tetanic responses by amygdala kindling stimulations in conscious and pentobarbital (PB)-treated rats. The entorhinal responses consisted of deep negative components and the following shallow positive components. The negative potential (mean +/- SE) reflecting excitatory synaptic activation in the test response evoked by a single stimulation (600 microA) before kindling stimulations was greater in PB-treated rats (1.3 +/- 0.21 mV, n = 6) than in conscious rats (0.5 +/- 0.08 mV, n = 9). The positive potential reflecting inhibitory synaptic activation in the test response was also greater in PB-treated rats (0.6 +/- 0.14 mV, n = 6) than in conscious rats (0.2 +/- 0.04 mV, n = 9). The magnitude of the tetanic response was estimated as the area between the excitatory negative potential and the baseline in the averaged tetanic response during each kindling stimulation (10 Hz, 100 pulses). The magnitude of the tetanic response was significantly enhanced in association with the prolongation of AD duration in the conscious rats. In the PB-treated (50 mg/kg intraperitoneally, i.p.) rats, enhancement of tetanic response was very slight and the progress of AD duration was prevented. There was a linear correlation (r = 0.9) between the magnitude of tetanic response and AD duration. These findings indicate that PB suppresses kindling-induced enhancement of excitatory synaptic activation in tetanic responses and that this enhancement is intimately related to the development of AD.
Hirayama
K
K
Department of Physiology, Osaka City University Medical School, Japan.
Murata
R
R
Matsuura
S
S
D000679:Amygdala / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D004558:Electric Stimulation; D018728:Entorhinal Cortex / Q000187:drug effects / Q000502:physiology*; D007696:Kindling, Neurologic / Q000187:drug effects*; D008297:Male; D010424:Pentobarbital / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects; D013746:Tetany / Q000139:chemically induced / Q000209:etiology*
D016194:Receptors, N-Methyl-D-Aspartate; D010424:Pentobarbital