The effect of anti-convulsant drugs on cognitive abilities.
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Biomedical subjects
Publications and source records attributed to M Trimble.
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To clarify the interrelationships of conversion symptoms, hysterical personality, sexual adjustment, and cerebral organic disorders the authors studied 89 patients with classic motor conversion symptoms (group L) and compared a subgroup of 24 of these patients (group H) with 24 matched control patients (group C). They found hysterical personality in 19% of group L, 21% of group H, and none of group C and passive-immature-dependent personality in 19% of group L, 21% of group H, and none of group C. Forty-eight percent of group L, 50% of group H, and 58% of group C had some cerebral disorder. Patients with conversion symptoms who also had hysterical and passive-immature-dependent personalities were especially likely to have sexual abnormalities.
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The literature dealing with the convulsant effects of the antidepressant drugs of the non-monoamine oxidase inhibitor variety is reviews. It is concluded that most of these drugs do lower the seizure threshold and may precipitate seizures even at normal therapeutic doses. The pathophysiology of antidepressant-induced seizures is discussed, and attention is drawn to biochemical differences in those antideprssants that have the least epileptogenic potential or may even be anticonvulsant. The clinical difficulties regarding administration of antidepressant drugs to epileptic patients are mentioned, and some practical advice is offered.
The effects of L-DOPA, L-tryptophan, monoamine oxidase inhibitor (MAOI), and MAOI plus L-tryptophan, each for 3 months, have been assessed in 10 severe, adult epileptics with placebo control. There was no overall reduction in seizure frequency, but 2 patients with minor partial seizures improved, 1 with L-DOPA, MAOI, and MAOI plus L-tryptophan, and the other with L-tryptophan and MAOI plus L-tryptophan. We have not been able to demonstrate an increased turnover of cerebral serotonin (5-HT), as measured by cerebrospinal fluid 5-hydroxyindoleacetic acid, after treatment with L-tryptophan for 3 months. This observation casts doubt on the ability of L-tryptophan to alter the long-term metabolism and functional activity of brain 5-HT. The importance of further exploration of manipulation of cerebral monoamines as a possible approach to the treatment of epilepsy is emphasized.
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Laboratroy and clinical evidence indicates that tricyclic antidepressants lower seizure threshold and in high doses may induce generalised seizures. In baboons with photosensitive epilepsy (Papio papio) the effects of 2 tricyclic antidepressants (imipramine and chlorimipramine) and of maprotiline and Nomi fensine have been studied (i.v. dose range 1-20 mg/kg. Imipramine, chlorimipramine and maprotiline (10 mg/kg i.v.) lowered seizure threshold to a comparable extent, whereas Nomifensine (10 mg/kg i.v-) did not enhance myoclinic responses to photic stimulation. Generalised seizures were seen 15-30 min after imipramine or chlorimipramine (20 mg/kg), and these two drugs showed no difference in their epileptogenicity. Administration of 5-hydroxytryptophan (25 mg/kg i.v.) 90 min before chlorimipramine or imipramine (10 mg/kg) completely blocked the usual augmentation of photically-induced epileptic responses. It is concluded that enhancement of serotoninergic activity following blockade of 5-HT re-uptake within the brain is unlikely to be responsible for enhanced myoclonic responses and epileptogenic seizures seen after tricyclic antidepressants. Nomifensine is significantly less epileptogenic than imipramine or chlorimipramine.
There has been much controversy in the past surrounding the relationship between schizophrenia and epilepsy. One hypothesis has been that the two disorders are antagonistic. The evidence supporting the antagonism hypothesis is briefly reviewed. A new theory based on current knowledge of the relationship of dopamine to both disorders is postulated which may explain the relationship between the psychosis and epilepsy which occurs in a subgroup of schizophrenic patients. In the light of this hypothesis it is suggested that further clinical work be undertaken to clarify further the exact association between the two disorders.
A patient is described who developed the classical syndrome of anorexia nervosa at the age of 52. Her illness occurred in relation to the marriages of her daughters and showed an extreme preoccupation with her body shape and a determination to slim by diet, purging and vomiting, and the hiding of food to the extent of rendering herself too weak to cope with the demands of her life. It is suggested that anorexia nervosa, though predominantly a disease of onset in adolescence, may present at any age and should be considered in the differential diagnosis of anorexia in patients over the age of 50.
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Neurophysiological studies employing drugs have been undertaken in the natural syndrome of photically induced epilepsy in the Senegalese baboon Papio papio. GABA-mediated inhibition, both pre- and posysynaptic, plays an important role in the epileptic manifestations seen in this syndrome synapses can significantly modify photically induced epileptic responses, partly as a result of changes in afferent activity. The level of activity in dopaminergic systems can also modify the epileptic signs. Among anticonvulsant drugs, barbiturates and benzodiazepines are very effective against this type of epilepsy, whereas many other drugs are weakly active or toxic. A modification of the natural model (using allylglycine as a priming agent) is convenient for correlating acute anticonvulsant activity and neurological toxicity with plasma concentrations of anticonvulsant agents.
Acute changes in spontaneous motor activity, the EEG and photically induced epileptic responses have been observed in baboons (Papio papio) following the i.v. injection of drugs acting on dopaminergic transmission. Apomorphine hydrochloride, 0.5-1.0 mg/kg, produced a phase of acute excitement with accentuated vigilance and abnormal buccal motor activity lasting 30-40 min; during this phase myoclonic responses to intermittent photic stimulation were absent. After piribedil (ET 495, 1,2'' -pyrimidyl-4-piperonylpiperazine), 2-10 mg/kg, acute excitement was not seen. Intermittent delta activity was prominent in the EEG for 1-3 hr, and was associated with a slight reduction in photically induced epileptic responses. Haloperidol 0.6-1.2 mg/kg, produced a long-lasting reduction in spontaneous motor activity with an increased incidence of spontaneous EEG spikes and waves and a great enhancement of paroxysmal EEG activity during photic stimulation. Pimozide, 0.5-2.5 mg/kg, normally produced mild sedation and some EEG slowing. 2 animals responded idiosyncratically to both haloperidol and pimozide, displaying intermittent dystonic episodes with bucco-facial dyskinesia. These findings suggest that activation of dopaminergic receptors can lead to a reduction in myoclonic responses to photic stimulation.