Behavioural reactions and changes in the spontaneous and evoked EEG-activity upon microinjection of noradrenaline and isoprenaline in cat nucleus raphe dorsalis.

Experiments are carried out on five cats with bipolar electrodes chronically implanted in various brain structures. The electrode intended to be introduced into raphe dorsalis is placed in a "guiding" isolated cannule. The spontaneous EEG-activity, the evoked potentials of photo- and electrostimulation as well as the behavioural reactions are studied for each animal before and after administration of noradrenaline (NA), isoprenaline (ISO) respectively, into nucleus raphe dorsalis (RD). The evoked potential are tape-recorded and averaged on Nicolet--1072 computer. Administration of NA in cat RD is followed by manifestations characterized by vegetative and motor symptoms and accompanied by EEG-changes. Desynchronization develops immediately after the injection of both NA and ISO in RD. The restoration of the amplitude-frequency characteristics of the EEG-activity take place in RD at the latest. Considerable changes are also observed in the evoked potentials recorded from the different structures. The EEG-changes observed after injection of NA, respectively ISO, in RD suggest functional connections between RD and the other brain structures studied. Both the EEG-changes and the observed behavioural reactions are probably largely based on the inhibition of the cerebral serotonin tonus by the catecholamines NA and ISO injected into RD and the resulting disruption of the balance between the adrenergic and serotoninergic cerebral systems.

Background neuronal activity in cat somatosensory cortex before and after VPL damage. Histogram and taxonomic analysis.

Two groups of cats under barbiturate anaesthesia are used to study the effect of electrolytic coagulation in the VPL of the thalamus on the extracellular unit activity in the somatosensory cortex (the focus of maximum activity (FMA) of this part of the nucleus affected by the lesion). In the first group of animals a comparison is made between the unit activity before and immediately after coagulation, while in the second group of animals the activity of the neurones, recorded in FMA of the intact VPL is compared with that of the neurones in the homologous symmetrical point in the hemisphere, ipsilateral to the VPL coagulate 10-14 days before the acute experiment. The activity of 246 neurones is studied. Histogram, statistical and taxonomic analyses are performed. It is found that lesion in VPL modifies to a certain extent the pattern of neuronal discharges, although even after the damage rhythmic groups of action potentials simultaneous with the spindle-like EEG waves are recorded in the primary somatosensory cortex (FMA). Evidently, the relay VPL nucleus is not the only pacemaker of spindle activity in its projection cortical area, which is in contradiction with some views expressed in the literature.

Participation of adrenergic mechanisms in the genesis of the cortical brain electrical activity.

The changes both in the spontaneous and in the evoked electrical activity of the somatosensory cortex, occurring after local or systematic administration of chlorpromazine, have been studied on 36 cats. The neuroleptic used weakens both the spontaneous cortical electrical activity and that induced by stimulation of n. radialis and of MRF. The potentials evoked by stimulation of VPL do not change. Systematic administration of chlorpromazine causes analogous changes in the electrical activity of the somatosensory cortex. Stimulation of n. radialis and MRF, though not of VPL, results in a sharp increase in the activity of the adenylate cyclase in the somatosensory cortex. Local administration of chlorpromazine leads to statistically significant less marked increase in response to applied stimulations of the adenylate cyclase activity. The results obtained substantiate the assumption that adrenergic neurones participate in the formation both of the spontaneous and of the induced electrical activity in the somatosensory cortex of cats.

[Comparative study of the changes in the EEG and cholinesterase activity in experimental Dipterex poisoning]. / Sravnitelno izsledvane na promenite v EEG i kholinesteraznata aktivnost pri eksperimentalna intoksikatsiia s diptereks.

A systematic study is conducted on cats, poisoned with the organophosphorus insecticide Dipterex. The changes in spontaneous and induced cortical activity along with those in serum and erythrocyte cholinesterase after intraperitoneal and intramuscular injection of Dipterex are investigated. Against the background of lowered cholinesterase activity, recorded in all the experiments , the changes in EEG appear to be discrete and inconstant. Uron single treatment with Dipterex, desynchronization prevails in the spontaneous EEG, whereas in the responses induced by light stimulants an increase of delayed negative potentiale prevails. Upon repeated Dipterex introduction, theta-like waves appear, associated with activation of paroxysmal manifestations existing in advance. Finally, the correlation between changes in cholinesterase activity and EEG is discussed.