Boletin de estudios medicos y biologicos最新文献

The present study describes the changes in electroencephalogram (EEG), behavior, and visual evoked potentials (VEPs) recorded in some structures of the limbic system of freely moving cats which had been administered two different doses of quipazine through different routes (5 mg/kg i.p. and 10 mg/kg i.v.). After the low dose of quipazine, the EEG from the cingulum developed a 6 c/s spike and wave activity. The amplitude of the P150 component of VEPs in the cingulum recording increased, while the VEPs recorded in visual cortex were barely affected. Simultaneously the animals displayed exploratory movements towards objects undetected by observers. The changes found in the cingulum with the tested doses may be due to specific actions of the drug on the polysensorial pathways. The high dose produced a rage reaction accompanied by a generalized spiking, intermixed with high voltage-low frequency waves, and an increase in VEPs in all recorded structures. At high doses the drug may be producing a discordance between the sensorial pathways and those in charge of the emotional processes.

The effects of intraperitoneal thyroxine administration (1 microgram/body weight) on postnatal days 1-3 and the subsequent alterations upon the development of six self-grooming components were measured postnatally in male Wistar rats between days 1-60. Observations on self-grooming components showed that thyroxine-treated rats did not show consistent significant differences in the duration of grooming movements of short displacement directed to the forepaws and head throughout the study, as compared to controls. By contrast, after weaning, the duration of grooming movements of long displacement directed to the fur, genital area, and body scratching were significantly increased. The findings suggest that early thyroxine treatment may primarily interfere with the neural circuitry that modulate long displacement grooming movements, rather than with the substrates controlling short displacement grooming activities. Thus, the hormone might be acting upon neural modulatory systems of self-grooming having different vulnerability in relation to the level of maturity of the brain circuits underlying each grooming component.

The influence of interruption of the visual input on acoustic habituation was studied in cats before and following the administration of quipazine, 3 mg/kg iv. The characteristics of acoustic habituation were analyzed through the magnitude and temporal course of multiunit activity (MUA) responses elicited in the mesencephalic reticular formation (MRF) by repetitive acoustic stimuli (70 db, 50 Hz trains of 2 sec duration) in 6 freely moving cats with cortical electrodes over the parietal cortex and bipolar electrodes chronically implanted in MRF and basolateral amygdala (AMN). The cats were submitted to repetitive acoustic stimulation during one 30 min period before, and three 30 min periods after drug administration in the following conditions: a) with unmasked eyes; b) with masked eyes by means of dark contact lenses. Persistent attentive behavior, catatonic attitudes, hypersynchronous (6 Hz, 100-150 microV) EEG activity and significant increase of spontaneous MUA in FRM and AMN were induced by quipazine both in the cats tested with unmasked and with masked eyes. This increase of MUA was higher immediately following drug administration and progressively decreased, although MUA values remained significantly higher than controls 110 min after quipazine administration. Acoustic habituation, evidenced through the progressive decrease of MUA responses of MRF to acoustic stimuli, was observed before quipazine administration when the cats were tested with unmasked and with masked eyes; as well as in cats tested with unmasked eyes following drug administration. However, the MUA responses to acoustic stimuli did not decrease in cats with masked eyes during acoustic stimulation periods 0-30 min and 40-70 min after quipazine administration.(ABSTRACT TRUNCATED AT 250 WORDS)

We report the effects exerted by the cortex upon the intralaminar thalamic nucleic, as revealed by reversible blockade of the cortex with spreading depression in awake rats. Extracellular recordings of spontaneous activity were made simultaneously at thalamic and cortical sites. The effect of peripheral receptive field stimulation was to decrease activity of intralaminar thalamic cells. Cortical recordings revealed the cortical regions affected by spreading depression. Two type of cells were identified depending on the changes in their sensorial responses during the cortical spreading depression propagation. The first exhibited a tonic facilitating cortical control when the cortical spreading depression was located at A 8.0 to A 10.0. The second type exhibited a disappearance of the sensorial responses when cortical spreading depression was located at A 4.0 to A 8.0 and also displayed the tonic facilitating control. This indicates that two different identified cortical regions influenced the thalamic activity.

Electron microscope studies demonstrated that soluble proteins (ferritin and horseradish peroxidase) administered in vitro to strips of guinea pig diaphragmatic muscle under physiological conditions were internalized by vesicles of primitive reticular cells (PRCs) found in the connective tissue. This endocytosis effect was enhanced when the muscle preparations were obtained from animals actively allergized to the protein. Denervation increased the occurrence of peroxidase-positive vesicles in the peroxidase-antiperoxidase system. These results suggest that the antigen-antibody interaction induces endocytosis directed to the specific antigen.