Adenosine inhibition of mesopontine cholinergic neurons: implications for EEG arousal

Increased discharge activity of mesopontine cholinergic neurons participates in the production of electroencephalographic (EEG) arousal; such arousal diminishes as a function of the duration of prior wakefulness or of brain hyperthermia. Whole-cell and extracellular recordings in a brainstem slice show that mesopontine cholinergic neurons are under the tonic inhibitory control of endogenous adenosine, a neuromodulator released during brain metabolism. This inhibitory tone is mediated postsynaptically by an inwardly rectifying potassium conductance and by an inhibition of the hyperpolarization-activated current. These data provide a coupling mechanism linking neuronal control of EEG arousal with the effects of prior wakefulness, brain hyperthermia, and the use of the adenosine receptor blockers caffeine and theophylline.

Calcium-antagonistic effects of carbamazepine in epilepsies and affective psychoses

Carbamazepine (CBZ) is known to have beneficial effects in the treatment of epilepsies and in the prophylaxis of affective disorders. Since increased transmembrane calcium fluxes and intracellular calcium concentrations play a key role in the generation of epilepsies and possibly also in the development of these psychiatric disorders the effects of CBZ on epileptic discharges (elicited by caffeine, penicillin and low Mg2+) in CA3 neurons of hippocampal slices were compared with those of the organic calcium antagonist verapamil and found to be almost the same.

Calcium antagonistic effects of carbamazepine as a mechanism of action in neuropsychiatric disorders: studies in calcium dependent model epilepsies

Carbamazepine (CBZ) is used in neurology for the treatment of epilepsies and trigeminal neuralgia and in psychiatry for the prophylactic treatment of affective and schizoaffective psychoses. Since a common mechanism of epilepsies and affective psychoses might be increased intracellular calcium ion levels, CBZ action was analyzed in penicillin, caffeine and low Mg2+ induced model epilepsies which have been shown to be suppressed specifically by organic calcium antagonists. In CA3 and CA1 areas of hippocampal slice preparations of guinea pigs CBZ reduced paroxysmal depolarizations and extracellular field potentials (EFP) in a typical time and concentration dependent manner as it is known from calcium antagonists. Furthermore, subthreshold concentrations of the organic calcium antagonist verapamil intensified the action of CBZ. NMDA induced increases of the discharge rate of EFP were, however, unaffected by CBZ.

[Importance of calcium ions and calcium antagonists in affective psychoses]

Apart from the eminent changes in the neurotransmitter systems of the central nervous system, a disturbance of the calcium ion concentration may be of significance in the pathophysiology of affective psychoses. The present paper deals with the contribution of calcium ions in the generation of affective psychoses and discusses the calcium antagonism as a new strategy in the treatment of the disease. The following topics will be described: 1. Disturbances of calcium metabolism in affective psychoses, 2. a comparison of lithium and carbamazepine effects, 3. clinical studies with organic calcium channel blockers in affective psychoses and 4. the role of calcium ions in affective psychoses.

Myoclonic epileptic seizures during clozapine treatment: a report of three cases

Three adult schizophrenic patients without a previous history of epilepsy are reported who, during clozapine treatment, developed paroxysmal EEG patterns and generalized myoclonic jerks without alteration of consciousness. These seizures were phenomenologically identical to those occurring in juvenile myoclonic epilepsy and were classified as generalized epileptic seizures. We tentatively conclude that generalized myoclonic epileptic seizures may be induced by clozapine.