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L G Stark

Publications and source records attributed to L G Stark.

At least 37 records · Page 2Linked to original sources
PubMed1983

Dose-dependent proconvulsant and anticonvulsant actions of the alpha 2 adrenergic agonist, xylazine, on kindled seizures in the rat.

The effects of the alpha 2 adrenergic agonist, xylazine, was evaluated on kindling acquisition and on kindled seizure expression in rats. Dose-dependent proconvulsant and anticonvulsant properties were found. The proconvulsant effects were observed at low (0.3 mg/kg) doses. In previously kindled rats these consisted of a decrease in afterdischarge threshold and an increase in the length and severity of the accompanying seizure. This dose also facilitated the rate of kindling in naive subjects. The anticonvulsant effects were observed at higher dose levels (3-20 mg/kg) which also produced sedation and ataxia. If these effects upon kindling are related to the adrenergic actions of xylazine, then it is proposed that the proconvulsant effects are associated with alpha 2 receptor activation and the anticonvulsant effects with alpha 1 receptor activation.

Amygdala↗
PubMed1983

Proconvulsant actions of lindane: effects on afterdischarge thresholds and durations during amygdaloid kindling in rats.

Daily exposure to lindane, 5 mg/kg, produced a number of consistent changes in rats undergoing amygdaloid kindling. Lindane decreased the number of afterdischarge-evoking stimulations required to produce the fully kindled state, increased the length of each successive afterdischarge during kindling and increased the severity of each convulsive response during kindling. However, lindane exposure did not change the total seconds of afterdischarge activity required to create the fully kindled state. In this study the enhancement of kindling rates by lindane stemmed primarily from an increase in the duration of epileptiform activity following each amygdaloid stimulation. These proconvulsant effects cannot be attributed to a lowering of seizure thresholds by lindane. Thresholds evaluated at different times during and after completion of kindling were either unaffected or actually elevated by lindane exposure. The length and severity of seizures evoked in fully kindled subjects by amygdaloid stimulation were much less affected by lindane exposure. This indicates that the most useful period for demonstrating proconvulsant activity with the kindling seizure model is during the dynamic phase of seizure development. Once the process has reached completion, seizures are maximally expressed, and their duration is controlled by processes not as susceptible to lindane exposures.

Amygdala↗
PubMed1983

The persistence of kindled amygdaloid seizures in rats exposed to lindane.

The persistence of the kindled seizure state produced during exposure to 5 mg/kg/day lindane was compared to that produced in nonexposed subjects. Persistence was evaluated at intervals of 2 weeks and 2 months. Rats were kindled on corn oil alone or corn oil + lindane until each rat exhibited a fully kindled seizure. Two weeks later subjects were tested for persistence using a crossover design where half the lindane-kindled rats were retested under lindane and the other half under oil. Two months later, subjects were retested again, without further exposure. The results demonstrate that the kindled state during lindane exposure was equally as stable and persistent as that produced under control conditions. This was true even though kindling required about 40% fewer trials with lindane exposure than without. The equivalence of the control and lindane kindled state is an important finding. It suggests that the proconvulsant action of lindane on kindling is not simply an additive one. Rather, lindane appears to directly increase the rte at which the permanent alterations in neuronal connectivity occur which are responsible for kindling expression.

Amygdala↗
PubMed1980

The kindled seizure: production of and modification by dieldrin in rats.

In the rat dieldrin can evoke a progressive increase in the severity of convulsive responses (kindling) during repetitive exposures that cannot be attributed to simple accumulation of dieldrin in the brain. It can also replace pentylenetetrazol as a kindling stimulus in previously pentylenetetrazol-kindled rats (cross-kindling). Chronic exposure to dieldrin facilitates kindling produced by daily electrical stimulation of the amygdala. Even single, acute exposure, can facilitate kindling produced by electrical stimulation of the amygdala, 1 to 3 weeks later. We propose that the procedure of kindling is a useful one with which to assess neurotoxicity. Agents affecting kindling in laboratory animals are of particular concern to those individuals in a population with demonstrable seizure susceptibility, those predisposed to convulsive disorders and others vulnerable to increased levels of CNS excitability.

Amygdala↗
PubMed1979

Anticonvulsant effects of benzhydryl piperazines on maximal electroshock seizures in rats.

The anticonvulsant effects of four benzhydryl piperazines, SC-13504 (ropizine, an anticonvulsant), hydroxyzine (HDX, an anxiolytic), chlorcyclizine (CCZ, an antihistaminic) and buclizine (BUC, an antihistaminic), were investigated utilizing a modified maximal electroshock seizure test in rats. In addition to detecting the presence or absence of tonic hindlimb extension, the modified method quantified various phases of the seizure. All four benzhydryl piperazines exhibited anticonvulsant activity in maximal electroshock seizure, but SC-13504 was similar in efficacy to phenobarbital and phenytoin, and much more effective than HDX, CCZ or BUC. Additionally, SC-13504 possessed a therapeutic index much greater than any of the compounds tested. The duration of action of the benzhydryl piperazines, in hours was: SC-13504, 0.5 to 8; HDX, 0.5 to 2; CCZ, 0.5 to 16; and BUC, 2 to 8. Buc and CCZ are postulated to be converted to active anticonvulsant metabolites.

Animals↗