Steroid anaesthesia: alphadione depresses multiunit activity in the mesencephalic reticular formation.

Cortical EEG and multiunit activity (MUA) of the mesencephalic reticular formation (MRF), area hypothalami anterior (AH) and the nucleus amygdalae basalis (AMY) were studied before and after different doses of alphadione (Althesin) and hexobarbitone (Evipan-Natrium) given to cats with chronically implanted electrodes. Non-anaesthetic doses of alphadione (0.15 ml/kg; 0.3 ml/kg; 0.6 ml/kg and 1.2 ml/kg i.p.) had sedative effects decreasing selectively the MUA in the MRF. In doses of 2.0 ml/kg, 2.4 ml/kg and 3.0 ml/kg i.p., alphadione induced anaesthesia which was associated with a rapid decrease of MUA in the MRF and by a gradual decrease of activity in the AH and AMY. The i.p. dose of 3.0 ml/kg abolished MUA responses of the reticular formation to acoustic, visual and somatic stimulation but failed to block responses to pain. Deep anaesthesia with lasting analgesia could be maintained by i.v. infusion (0.075 ml/kg/min). This procedure blocked the responsiveness to painful stimulation while pharyngeal and laryngeal reflexes were maintained. Hexobarbitone in a dose of 20.0 mg/kg i.p. did not produce anaesthesia in the cat. Administration of 40.0 mg/kg i.p. resulted in a rapid decrease of MUA in the MRF, AH and AMY, MUA responses to each stimulation were abolished and the pharyngeal reflex was blocked.

Effects of drugs influencing the cAMP level on hippocampal seizure activity.

Changes of hippocampal EEF seizure activity elicited by electrical stimulation of the hippocampus or penicillin injection into the hippocampus were investigated under the effect of locally applied drugs influencing the cAMP level in the brain. It was observed that some drugs which elevate the cAMP level such as papaverine, histamine +K+ and dibutyryl cAMP elevated the electric seizure threshold while in penicillin-induced epilepsy they reduced the occurrence of ictal activity and the interictal spike frequency. These drugs when applied before penicillin prolonged the time necessary for development of the epileptic focus. The effect of imidazole was the opposite in every respect. On the basis of these data the possible role of cAMP in the pathomechanism of epilepsy is discussed.

Early postnatal development of wakefulness-sleep cycle and neuronal responsiveness: a multiunit activity study on freely moving newborn rat.

The development of the wakefulness-sleep cycle and neuronal responsiveness was studied on freely moving 1-, 3-, 5- and 7-day-old rats. Semimicroelectrodes were implanted under ether anaesthesia for multiunit activity (MUA) recording from the mesencephalic reticular formation (MRF) and basal forebrain area (FB). Following recovery from surgery and between the recording sessions pups were put back to the nest to be fed by their mothers. In a temperature-controlled environment continous MUA records were made between 16:00-18:00 and 19:00-21:00 h. In the MRF and FB the MUA was high during wakefulness, it decreased to a stable low level in quiet sleep and appeared to reach the highest values in paradoxical sleep. Neurone populations in the MRF and FB responded to somatosensory (air puffs), visual (flicker) and acoustic (1100 Hz) stimulation by a significant increase of MUA from the first day of life. In the MRF the rate of responsiveness increased during the first postnatal week; however, MUA responses to different stimuli exhibited different developmental time-courses. A high rate of responsiveness to each stimulus was characteristic of FB units. This neonatal 'supersensitivity' tended to decrease with age and the time-course of developmental changes proved to be modality-dependent.

The developing mesencephalic reticular formation: changes in responsiveness during ontogeny of the rat.

Multiunit activity (MUA) of the mesencephalic reticular formation (MRF) was recorded on freely moving 1 to 21-days-old young as well as adult rats. Consistent state-dependent changes in the frequency of amplitude discriminated cell discharges were observed in association with wakefulness and sleep cycle from the first day of life, and MRF neuron populations were found to gain adult-like functional characteristics of spontaneous activity by the 9th-11th postnatal day. MRF units were capable of responding to somatosensory, visual and acoustic stimulation by a significant activation from Day 1. As development proceeded, rate of responsiveness appeared to increase, however, MUA responses to different sensory modalities exhibited different developmental time-courses. High rate of responsiveness to somatosensory stimulation was characteristic of the newborn rat. Magnitude of somatosensory responses increased remarkably during the first three postnatal days reaching adult values around this age and only moderate alteration of response patterns could be detected afterwards. The MRF MUA responses to visual and acoustic stimulation increased during the first week of life and, following a striking decline of responsiveness occurring at the time of opening of eyes and external auditory meati (Day 13), visual and acoustic responses gained the adult properties by the 17th-19th postnatal day.

Multiunit activity in the mesencephalic reticular formation and septal area of freely moving newborn rat.

A surgical technique to implant stereotaxically fixed probes for recording multiunit activity /MUA/ from the mesencephalic reticular formation and septal area of freely moving 6--12 hr old newborn rat is described. In both brain areas the spontaneous firing of neuron populations showed close correlation with the stages of wakefulness and sleep cycle.

Investigation of adaptive processes in child and adolescent swimmers. Acid-base parameters of swimmers and weight-lifters.

Acid-base parameters of adolescent swimmers (capacitive sport) and of adult weight-lifters (athletoid sport) were investigated before and after training in the submaximally trained phase of a year-round training period. In swimmers, training induced incompensated metabolic acidosis, which persisted at 10 min after the training. This acidosis showed no correlation to the blood lactate level. In weight-lifters, there was only a slight, compensated posttraining acidosis, which tended to decrease 10 min after the training. The weight-lifters had extremely high posttraining ammonia levels. It might be supposed that ammonia-genesis has a role in the compensation of exercise-induced acidosis in weight-lifters. The differences in acid-base status of swimmers and weight-lifters might be related to the different breathing mechanism needed for the two different sports.

Adaptive processes in child and adolescent swimmers. Blood coagulation and viscosity.

Multifactorial studies were performed in child and adolescent swimmers in the early period of training and in a submaximum state of training in the year's racing period. Blood coagulation, viscosity, acidity, protein metabolism, muscle enzymes, ions, haematologic, cardiac and endocrine parameters have been investigated. In the early period of training, physical exercise resulted in fibrinolysis, and a decrease in the fibrinogen and prothrombin levels and the platelet count. The same exercise in fully-trained organisms failed to produce such changes. Data concerning acidity, protein metabolism, muscle enzymes, ions, haematologic, cardiac and endocrine parameters will be published in subsequent papers.

Effect of dopamine on the hypothalamo-pituitary-adrenocortical system after injection in the nucleus raphe dorsalis.

Dopamine (DA) injected into the dorsal raphe nucleus (DRN) increased plasma corticosterone (PCS) level as well as serotonin (5-HT) content in the mesencephalon and hippocampus 30 min after the administration. At the same time, 5-HT content of the hypothalamus was decreased. A stress applied 2 min after the injection elevated PCS level but diminished hypothalamic 5-HT content in control, but not in DA-treated animals. PCS level and 5-HT content of the hypothalamus in DA-treated + stressed animals did not differ from the values found in DA-treated rats, but mesencephalic and hippocampal 5-HT content did not increase. It is concluded that DA injected into the DRN suppresses the response to stress of the hypothalamo-pituitary-adrenocortical system.

Dose-dependent dual effect of corticosterone on cerebral 5-HT metabolism.

The action of 1.0 and 10.0 mg/kg (i.p.) of corticosterone on serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) contents and on serotonin turnover, measured by an MAO-inhibitor method, was studied at 30 and 120 min after administration. A 1.0 mg/kg dose of corticosterone increased the serotonin content and turnover in the hypothalamus and mesencephalon 30 min after administration; however, it was ineffective on dorsal hippocampus and frontal and parietal cortex. 5-HIAA content did not change significantly in any of the brain areas studied. A 10.0 mg/kg dose of corticosterone decreased the serotonin content and turnover in the hypothalamus and mesencephalon; it was ineffective in other brain areas investigated. 5-HIAA content significantly decreased in the hypothalamus while it increased in the mesencephalon and dorsal hippocampus. In the parietal and frontal cortex, 5-HIAA content did not change following administration of 10.0 mg/kg of corticosterone. At 120 min after corticosterone administration, neither 5-HT content and turnover nor 5-HIAA content showed any change in the brain areas investigated. The results suggest that corticosteroids might change the activity of the brain serotoninergic system in a dose- and time-dependent manner, and in this way the serotoninergic system might play an important role in mediation of the corticosteroid effect exerted on brain function.

Effect of thyrotropin-releasing hormone (TRH) and antidepressant agents on brain stem and hypothalamic multiple unit activity in the cat.

The EEG and MUA (multiple unit activity) of mesencephalic reticular formation (MRF), area hypothalami posterior (PH), and area hypothalami anterior (AH) were studied in chronically implanted freely moving cats. The effects of thyrotropin-releasing hormone (TRH) and some antidepressant agents were tested on neuronal activity. Desipramine and imipramine resulted in a dose-dependent decline of MUA of all structures with the most significant decrease of activity in PH. A single injection of TRH resulted in slight or moderate gross behavioral changes and vegetative excitation lasting for 30-50 min with variable MUA levels. In the course of repetitive TRH treatment on consecutive days the gross behavioral changes and the vegetative symptoms failed to develop by the 3rd or 4th day. By that time the MUA changes of PH and MRF showed similar characteristics in response to TRH administration which was observed following the injection of desipramine and imipramine. The drugs, except for TRH, induced a suppression of paradoxical sleep cycles.

Inhibitory action of midbrain raphe stimulation on stress-induced elevation of plasma corticosterone level in rats.

Electric stimulation of rat midbrain raphe nuclei by means of chronically implanted bipolar electrodes was able to reduce the stress-induced increase in plasma corticosterone level by about 40-50%. A serotonin receptor blocker, methysergide, prevented the stimulation-induced inhibition of the stress response. The results support the possible existence of serotoninergic inhibition of hypothalamo-pituitary-adrenocortical activation in rats.