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Dexamethasone effect on hippocampal RSA in rabbits
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deteriorated the instrumental performance. This d e t e r i o r a t i o n not only concerned alimentary responses, but also instrumental reactions based on fear (avoidance) and on social reinforcement. Amphetamine produced also a decrease of heart rate and attenuated i t s acceleration to the conditioned s t i m u l i , which was observed before treatment. Chlorpromazine (I mg/kg) treatment resulted in a detectable improvement of the performance which was disturbed by neurotic state. On the other hand, instrumental performance of responses reinforced by sensory social reward ( t a c t i l e s t i m u l i given by the experimenter), which was completely abolished a f t e r amygdala damage was not r e s t i t u t e d by the a p p l i c a t i o n of c h l o r promazine. Also avoidance and alimentary performance was not r e s t i t u t e d in l e sioned animals. Strong i n d i v i d u a l differences were observed in the r e a c t i v i t y of the dogs to the p a r t i c u l a r drug, and concerning a l l three investigated motivations. These r e s u l t s i n d i c a t e that the changes in instrumental performance are not due to the general e x c i t a t o r y or sedative e f f e c t of the drug's action. Contrary to our assumption, the amphetamine which was supposed to have an e x c i t a t o r y e f f e c t , deteriorated the performance of learned responses based on three d i f ferent motivations and produced heart rate deceleration. Imipramine, produced augmented m o t i l i t y and improvement of instrumental motor performance, but l e f t emotional signs of depression unchanged. Chlorpromazine instead of producing a sedative e f f e c t , in some cases d e f i n i t e l y improved
the performance. In some
others i t reduced the generalized avoidance reactions. These r e s u l t s suggest that the mechanisms underlying behavioural disturbances are not due to changes of the level of arousal.
DEXAMETHASONEEFFECT ON HIPPOCAMPALRSA IN RABBITS FONTANI, G., FARABOLLINI, F. AND GRAZZI, F. I s t i t u t o di F i s i o l o g i a Umana, Universit~ di Siena, Siena, I t a l y There is evidence of a b i p o l a r i n t e r a c t i o n between the hippocampus and the adreno-cortical f u n c t i o n . This i n t e r a c t i o n seems to be important in modulating the behavioral response to s i g n i f i c a n t environmental s t i m u l i .
In d i f f e r e n t ani-
mal species c o r t i c o s t e r o i d administration is e f f e c t i v e in modifying hippocampal electrical activity.
In the r a b b i t , RSA (rhythmic slow a c t i v i t y ,
theta rhythm)
represents an important component of the hippocampal EEG and eppears to be a f fected by the presentation of d i f f e r e n t s t i m u l i and by neurotransmitter
192
manipulation
. In the present experiment, the effects of the synthetic gluco-
corticoid dexamethasone (DEX) (chronically injected 0.2 mg/kg i.p./day, during 8 days following pre-test controls) on RSA have been studied. RSA has been analyzed according to the following parameters: total amount, single episode duration and frequency. Experiments were carried out while the rabbit was in the experimental cage (neutral environment) and then presented with a sequence of immobile (an object containing an odorous vegetable branch and a stuffed sparrowhawk) and mobile (a l i v e cat) stimuli. In a l l the experimental conditions studied, DEX did not modify neither RSA amount nor single RSA episode duration, whereas RSA frequency was s i g n i f i c a n t l y decreased both during immobility (mean values: 6.3 Hz vs 6.5 Hz) and movements (7 Hz vs 7.2 Hz). Exploratory a c t i v i t y was reduced only in presence of the object. On the basis of the supposed i n t e r action between catecholamines and pituitary-adrenal axis, another group of animals was treated with DEX in combination with DSP 4, a noradrenaline neurotoxin, injected in a single dose (40 mg/kg i . p . ) 10 days before the test. The s i g n i f i 2 cant reduction of RSA amount previously observed by injecting DSP4 alone , was abolished by DEX, while the reduction in frequency both during immobility (5.8 Hz after treatment vs 6 Hz in the pre-treatment controls) and movements (6.8 Hz vs 6.9 Hz) was maintained. As for the d i s t r i b u t i o n of RSA frequency values, there was a reduction in the high frequency band an an increase in the low frequency one both after DEX and DEX *DSP4. Results suggest that hippocampal RSA, in response to different s t i m u l i , is modulated by DEX either through a direct effect on hippocampal receptors or through i t s effect on ACTH. Moreover, an interaction between noradrenaline and glucocorticoids in modulating RSA amount and frequency could be suggested. REFERENCES I. Farabollini, F., Fontani, G. and Carli, G., Behav. Brain Res. (In press) 2. Fontani, G., Farabollini, F. and Dari, A., Behav. Brain Res. (In press) *
DSP4 has been supplied by Astra Lakemedel AB, Sweden.
CHANGES IN SPINE DENSITY ON HUMANVISUAL CORTICAL NEURONSDURING DEVELOPMENT GAREY, L.J., MICHEL, A.E.* AND LEUBA, G. I n s t i t u t e of Anatomy and *Division of Neuropathology, University of Lausanne, 1011 Lausanne, Switzerland The density of spines was measured on apical dendrites of pyramidal neurons with their soma in layer I l l of human visual cortex (area 17). Blocks of cortex
deteriorated the instrumental performance. This d e t e r i o r a t i o n not only concerned alimentary responses, but also instrumental reactions based on fear (avoidance) and on social reinforcement. Amphetamine produced also a decrease of heart rate and attenuated i t s acceleration to the conditioned s t i m u l i , which was observed before treatment. Chlorpromazine (I mg/kg) treatment resulted in a detectable improvement of the performance which was disturbed by neurotic state. On the other hand, instrumental performance of responses reinforced by sensory social reward ( t a c t i l e s t i m u l i given by the experimenter), which was completely abolished a f t e r amygdala damage was not r e s t i t u t e d by the a p p l i c a t i o n of c h l o r promazine. Also avoidance and alimentary performance was not r e s t i t u t e d in l e sioned animals. Strong i n d i v i d u a l differences were observed in the r e a c t i v i t y of the dogs to the p a r t i c u l a r drug, and concerning a l l three investigated motivations. These r e s u l t s i n d i c a t e that the changes in instrumental performance are not due to the general e x c i t a t o r y or sedative e f f e c t of the drug's action. Contrary to our assumption, the amphetamine which was supposed to have an e x c i t a t o r y e f f e c t , deteriorated the performance of learned responses based on three d i f ferent motivations and produced heart rate deceleration. Imipramine, produced augmented m o t i l i t y and improvement of instrumental motor performance, but l e f t emotional signs of depression unchanged. Chlorpromazine instead of producing a sedative e f f e c t , in some cases d e f i n i t e l y improved
the performance. In some
others i t reduced the generalized avoidance reactions. These r e s u l t s suggest that the mechanisms underlying behavioural disturbances are not due to changes of the level of arousal.
DEXAMETHASONEEFFECT ON HIPPOCAMPALRSA IN RABBITS FONTANI, G., FARABOLLINI, F. AND GRAZZI, F. I s t i t u t o di F i s i o l o g i a Umana, Universit~ di Siena, Siena, I t a l y There is evidence of a b i p o l a r i n t e r a c t i o n between the hippocampus and the adreno-cortical f u n c t i o n . This i n t e r a c t i o n seems to be important in modulating the behavioral response to s i g n i f i c a n t environmental s t i m u l i .
In d i f f e r e n t ani-
mal species c o r t i c o s t e r o i d administration is e f f e c t i v e in modifying hippocampal electrical activity.
In the r a b b i t , RSA (rhythmic slow a c t i v i t y ,
theta rhythm)
represents an important component of the hippocampal EEG and eppears to be a f fected by the presentation of d i f f e r e n t s t i m u l i and by neurotransmitter
192
manipulation
. In the present experiment, the effects of the synthetic gluco-
corticoid dexamethasone (DEX) (chronically injected 0.2 mg/kg i.p./day, during 8 days following pre-test controls) on RSA have been studied. RSA has been analyzed according to the following parameters: total amount, single episode duration and frequency. Experiments were carried out while the rabbit was in the experimental cage (neutral environment) and then presented with a sequence of immobile (an object containing an odorous vegetable branch and a stuffed sparrowhawk) and mobile (a l i v e cat) stimuli. In a l l the experimental conditions studied, DEX did not modify neither RSA amount nor single RSA episode duration, whereas RSA frequency was s i g n i f i c a n t l y decreased both during immobility (mean values: 6.3 Hz vs 6.5 Hz) and movements (7 Hz vs 7.2 Hz). Exploratory a c t i v i t y was reduced only in presence of the object. On the basis of the supposed i n t e r action between catecholamines and pituitary-adrenal axis, another group of animals was treated with DEX in combination with DSP 4, a noradrenaline neurotoxin, injected in a single dose (40 mg/kg i . p . ) 10 days before the test. The s i g n i f i 2 cant reduction of RSA amount previously observed by injecting DSP4 alone , was abolished by DEX, while the reduction in frequency both during immobility (5.8 Hz after treatment vs 6 Hz in the pre-treatment controls) and movements (6.8 Hz vs 6.9 Hz) was maintained. As for the d i s t r i b u t i o n of RSA frequency values, there was a reduction in the high frequency band an an increase in the low frequency one both after DEX and DEX *DSP4. Results suggest that hippocampal RSA, in response to different s t i m u l i , is modulated by DEX either through a direct effect on hippocampal receptors or through i t s effect on ACTH. Moreover, an interaction between noradrenaline and glucocorticoids in modulating RSA amount and frequency could be suggested. REFERENCES I. Farabollini, F., Fontani, G. and Carli, G., Behav. Brain Res. (In press) 2. Fontani, G., Farabollini, F. and Dari, A., Behav. Brain Res. (In press) *
DSP4 has been supplied by Astra Lakemedel AB, Sweden.
CHANGES IN SPINE DENSITY ON HUMANVISUAL CORTICAL NEURONSDURING DEVELOPMENT GAREY, L.J., MICHEL, A.E.* AND LEUBA, G. I n s t i t u t e of Anatomy and *Division of Neuropathology, University of Lausanne, 1011 Lausanne, Switzerland The density of spines was measured on apical dendrites of pyramidal neurons with their soma in layer I l l of human visual cortex (area 17). Blocks of cortex