Serotonergic influences on EEG synchronization induced by milk drinking in the cat

Milk drinking elicits electroencephalographic (EEG) synchronization in the parieto-occipital cortex of cats. This EEG change is a reliable correlate of the consummatory phenomena involved in "relaxation" behavior. The effect of varying serotonin brain levels by administering P-chlorophenylalanine (PCPA) or 5-hydroxytryptophan (5HTP) on this response was studied in 25 young cats. Single or repeated injections (4-8 days) of 50, 100 or 150 mg/kg of PCPA resulted in a dose related decrease in the duration of the EEG parieto-occipital synchronization during fixed periods of milk drinking. A single injection of 3, 10 or 30 mg/kg of 5HTP to chronic PCPA treated cats, restored the EEG parieto-occipital synchronization during milk drinking to control values. Moreover, administration of 5HTP to non-treated cats significantly increased the duration of EEG parieto-occipital synchronization during milk drinking. Our results suggest that brain serotonergic neurons are involved in the development of EEG synchronization during milk drinking.

Nonlinear optical interferometer

The interferometer described, based on the second harmonic generation of light, is useful in the contouring of refractive objects with large variations in optical depth. The device is a real-time common-path self-referencing interferometer that yields interferograms in the visible with an equivalent wavelength of the order of 50 microm. We describe experiments that show that it can serve as a useful device. The key to the device is the use of Y-cut LiNbO(3) configured for surface acoustooptic applications rather than for conventional second harmonic applications. The crystals are noncritically phase matched by temperature control and are used with a repetitively pulsed Nd:YAG laser operating at 1.06 microm.

Antithrombin III contribution to cholestasis differential diagnosis: its correlation with one stage prothrombin time and factor V

Levels of antithrombin III (AT III) measured by two different methods, Factor V (FV) and One Stage Prothrombin Time, have been studied in two groups of patients: 55 with chronic liver disease and 22 with extra hepatic cholestasis. Results show a statistically significant correlation between the decrease of AT III and FV in the first group, and the normality of these parameters (unrelated to One Stage Prothrombin Time) in the second group. Levels at AT III and FV correlate directly with the functional integrity of hepatic parenchyma, so they may help in the differential diagnosis of different types of cholestasis.

Changes in multiunit activity and EEG induced by the administration of natural progestins to flaxedil immobilized cats

The effects of progesterone (P) and 7 of its metabolites on the EEG and multiunit activity (MUA) of various limbic structures were studied in flaxedil immobilized cats. Most progestins inhibited the MUA of the mesencephalic reticular formation, hippocampus and hypothalamus and induced cortical EEG synchronization. MUA changes in the mesencephalic reticular formation frequently preceded EEG synchronization. Progestins reduced in the 5 beta postition (pregnanolone, epipregnanolone and pregnanedion) inhibited neuronal discharge and synchronized EEG activity with shorter latencies and in lower doses than those reduced in the 5 alpha position (allopregnanolone and allopregnanedion). Progestins having the delta 4,3-keto structure (P, 20 alpha-hydroxy pregnenone, 20 beta-hydroxy pregnenone) induced electrophysiological changes with prolonged latencies and in doses significantly higher than ring A reduced progestins. Administration of epipregnanolone to "cerveau isole" preparations depressed neuronal firing in those structures located rostral to the level of the brain stem transection (hypothalamus, hippocampus), but failed to increase the already synchronized cortical activity. These results suggest that: a, ring A reduction increases the capacity of P and other delta 4,3-keto progestins to inhibit neuronal discharge in certain brain areas and b, changes in neuronal firing induced by progestins are not necessarily mediated through the cat brain stem reticular formation.

Analysis of various factors involved in EEG synchronization during milk drinking in the cat

Electroencephalographic (EEG) and multineuronal activity (MUA) from several brain structures were recorded in 11 adult cats during milk drinking. Milk drinking elicited parietal and hippocampal EEG synchronization and inhibited multiunit discharge in several brain regions. The proportion of EEG synchronization varied considerably between animals, but remained more or less constant for each cat after several testing days. Neither modification of milk concentration nor fasting influenced the proportions of EEG synchronization during milk drinking. Adaptation of the animals to the experimental environment facilitated the appearance of EEG synchronization during milk drinking. Chlorpromazine (3 mg/kg) significantly increased the proportion of EEG synchronization observed during milk drinking. By contrast, displacement of the head, neck or postural body adjustments during milk drinking blocked EEG synchronization. Amphetamine also had a suppressive effect on the EEG parietal and hippocampal synchronic activity observed during milk drinking. Our results suggest that development of parietal EEG synchronization in response to pleasant stimulation is a complex phenomenon requiring a relaxed condition of the animal, including its adaptation to the experimental environment and relative immobility with the concomitant diminution of afferent inflow from some of the muscles involved in locomotion.