- Email: [email protected]
Gender differences in exploration and neophobia in the young rat. Effect of an early septal lesion
201
Reduced c h o l i n e r g i c a c t i v i t y
has been found in d i f f e r e n t brain areas in the strong growth hor-
mone, t h y r o i d s t i m u l a t i n g hormone and p r o l a c t i n d e f i c i e n t Snell dwarf mouse. The e f f e c t of the mut a n t ' s p i t u i t a r y d e f i c i e n c y on c h o l i n e r g i c mechanisms appears to be s e l e c t i v e : areas showing normally high c h o l i n e r g i c a c t i v i t y
such as s t r i a t u m , o l f a c t o r y tubercles and, to a lesser e x t e n t , hippo-
campus, e x h i b i t severe c h o l i n e r g i c neurotransmission impairment. Cortical areas, however, as well as hypothalamus, pons medulla and cerebellum are l i t t l e ,
i f at a l l ,
a f f e c t e d . The lack of p i t u i t a r y
hormones seems to also e f f e c t choline a c e t y l t r a n s f e r a s e (CHAT) a c t i v i t y the
achievement of high a f f i n i t y
in hippocampus and s t r i a t u m .
and/or synthesis as well as
(H.A.) c h o l i n e r g i c uptake mechanisms, both s t r o n g l y defecti
I t is relevant to note that in striatum and hippocampus
tude of decrease in ChAT a c t i v i t y
the magni-
p a r a l l e l s the size of reduction of the v e l o c i t y of choline uptake.
This may r e f l e c t a lower density in c h o l i n e r g i c neurons or in c h o l i n e r g i c nerve terminals in the dwarf mouse. At the postsynaptic l e v e l , the s e n s i t i v i t y of muscarinic receptors is shown to be increased, possibly r e f l e c t i n g a compensatory mechanism with regard to the d e f i c i t activity.
in c h o l i n e r g i c presynaptic
A c e t y l c h o l i n e s t e r a s e , the a c e t y l c h o l i n e degradation enzyme is not affected.
I t is i n t e r e s t i n g to also note that in these strong c h o l i n e r g i c d e f i c i e n t s t r u c t u r e s of the dwarf mutant abnormally high somatostatin l e v e l s , a neurohormone and/or modulator, were observed. These r e s u l t s are discussed with regard to the behavioural disturbances, the dwarf mutant e x h i b i t s , e s p e c i a l l y locomotor impairments and memory d e f i c i e n c y . Thus the h y p o a c t i v i t y of the mutant ( I ) may be p a r t l y related to decreased c h o l i n e r g i c a c t i v i t y and a l t e r e d
somatostatinergic r e g u l a t i o n in the n i g r o s t r i a t a l
loop.
With respect to previous r e s u l t s ( 2 ) , the strong c h o l i n e r g i c d e f i c i e n c y in the septo-hippocampal pathway, the dwarf mutant e x h i b i t s , could be linked to i t s defect in memory a b i l i t y . REFERENCES I . Bouchon, R. and W i l l , B., Physiol. Behav., 28 (1982) 971. 2. Ebel, A. et a l . C.R. Acad. S c i . , 283 (1976) 535.
GENDER DIFFERENCES IN EXPLORATION AND NEOPHOBIA IN THE YOUNG RAT. EFFECT OF AN EARLY SEPTAL LESION ECLANCHER, F. AND ANGST, M.J. Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, 5, Rue Blaise Pascal, 67084 Strasbourg C#dex, France When placed in an open f i e l d at 20, 30, and 40 days of age, group-raised Wistar rats were found to d i s p l a y at 30 days a p a r t i c u l a r l y high level of responsiveness (ambulation and r e a r i n g s ) , with no d i f f e r e n c e between males and females. A septal l e s i o n performed at 6 days of age resulted in a c l e a r increase of the locomotor a c t i v i t y
already at 20 days of age. Gender d i f f e r e n c e s appeared in septal
r a t s , the females being more a c t i v e than the males at e i t h e r age, and the males rearing more often than the females at 30 days of age.
202
When the rats were given at 30 days the p o s s i b i l i t y
to choose between entering f r e e l y a novel
chamber or staying in the f a m i l i a r one, control rats showed neophobia (the males more than the f e males) while septal rats did not, whatever the gender of the animals. On the f i r s t t e s t , the locomotor a c t i v i t y
minute of the
displayed by septal rats in the f a m i l i a r chamber as well as in the no-
vel one was higher than that of control r a t s . This a c t i v i t y of control r a t s .
decreased afterwards to reach the l e v e l s
These r e s u l t s show that the septum is i n v o l v e d , at very early stages of the ontogenesis of the r a t , in the i n h i b i t o r y control over responsiveness to an unavoidable novel environment ( open f i e l d ) as well as in the induction of neophobia towards an avoidable one. But i t seems that t h i s limbic s t r u c t u r e does not intervene at an e a r l y age in the mediation of sexual hormone-induced d i f f e r e n t i a l modulation of r e a c t i v i t y
in the female and male young rats confronted to the open f i e l d .
DETECTION OF STATIONARY AND MOVING VISUAL PATTERNS IN THE PIGEON EMMERT, K.-H. Abteilung f u r Vergleichende Neurobiologie, U n i v e r s i t ~ t Ulm, D-7900 Ulm, Germany In a psychophysical experiment visual pattern detection of pigeons was analysed by means of the s i g n a l - d e t e c t i o n theory. Pigeons were trained to d i s c r i m i n a t e geometrical patterns ( p o s i t i v e stimulus: c i r c l e ;
negative
stimulus: rhomb) superimposed with Gaussian noise. During the experimental sessions the animals were free to move in the t e s t box. The number of correct choices was measured in r e l a t i o n to d i s t i n c t s i g n a l - t o - n o i s e r a t i o s (S/N), obtained by varying the signal i n t e n s i t y . From these data detection p r o b a b i l i t y (PD) was calculated as a f u n c t i o n of S/N. For analysis S/N at PD50 (75% correct choices) of each animal was applied. The performance f o r d i s c r i m i n a t i n g s t a t i o n a r y patterns reached PD50 at S/N - 1.6 (mean of e i g h t animals). This r e s u l t corresponds to that obtained in the cat when tested in the same s i t u a t i o n ( I ) . Pattern
movement is found to increase the performance only s l i g h t l y
contrast to mammals ( c a t : f a c t o r 4 . . 5 )
( f a c t o r 1 . 6 ) , which is in
(2); man: f a c t o r 10 (3).
The size of the pattern seems to have only a s l i g h t influence on the detection p r o b a b i l i t y . When the width of the patterns was altered by a f a c t o r of 0.29, S/N at reference PD was nearly unchanged in about 75% of the animals in e i t h e r case. To decide whether or not a signal was presented in the noise the pigeons needed lower S/N than they did f o r equivalent d i s c r i m i n a t i o n tasks ( s t a t i o n a r y pattern: f a c t o r 3.1, moving p a t t e r n : f a c t o r 4.3).
In a d d i t i o n , observations of the animals during the t e s t seem to i n d i c a t e that the pigeons
analysed the s t i m u l i with t h e i r A r e a e D o r s a l e s .Thus, the c o r r e l a t i o n of our psychphysical measurements with the behavioural observations support the hypothesis about f u n c t i o n a l properties of the Area d o r s a l i s proposed by Martinoya et a l .
(4).
Reduced c h o l i n e r g i c a c t i v i t y
has been found in d i f f e r e n t brain areas in the strong growth hor-
mone, t h y r o i d s t i m u l a t i n g hormone and p r o l a c t i n d e f i c i e n t Snell dwarf mouse. The e f f e c t of the mut a n t ' s p i t u i t a r y d e f i c i e n c y on c h o l i n e r g i c mechanisms appears to be s e l e c t i v e : areas showing normally high c h o l i n e r g i c a c t i v i t y
such as s t r i a t u m , o l f a c t o r y tubercles and, to a lesser e x t e n t , hippo-
campus, e x h i b i t severe c h o l i n e r g i c neurotransmission impairment. Cortical areas, however, as well as hypothalamus, pons medulla and cerebellum are l i t t l e ,
i f at a l l ,
a f f e c t e d . The lack of p i t u i t a r y
hormones seems to also e f f e c t choline a c e t y l t r a n s f e r a s e (CHAT) a c t i v i t y the
achievement of high a f f i n i t y
in hippocampus and s t r i a t u m .
and/or synthesis as well as
(H.A.) c h o l i n e r g i c uptake mechanisms, both s t r o n g l y defecti
I t is relevant to note that in striatum and hippocampus
tude of decrease in ChAT a c t i v i t y
the magni-
p a r a l l e l s the size of reduction of the v e l o c i t y of choline uptake.
This may r e f l e c t a lower density in c h o l i n e r g i c neurons or in c h o l i n e r g i c nerve terminals in the dwarf mouse. At the postsynaptic l e v e l , the s e n s i t i v i t y of muscarinic receptors is shown to be increased, possibly r e f l e c t i n g a compensatory mechanism with regard to the d e f i c i t activity.
in c h o l i n e r g i c presynaptic
A c e t y l c h o l i n e s t e r a s e , the a c e t y l c h o l i n e degradation enzyme is not affected.
I t is i n t e r e s t i n g to also note that in these strong c h o l i n e r g i c d e f i c i e n t s t r u c t u r e s of the dwarf mutant abnormally high somatostatin l e v e l s , a neurohormone and/or modulator, were observed. These r e s u l t s are discussed with regard to the behavioural disturbances, the dwarf mutant e x h i b i t s , e s p e c i a l l y locomotor impairments and memory d e f i c i e n c y . Thus the h y p o a c t i v i t y of the mutant ( I ) may be p a r t l y related to decreased c h o l i n e r g i c a c t i v i t y and a l t e r e d
somatostatinergic r e g u l a t i o n in the n i g r o s t r i a t a l
loop.
With respect to previous r e s u l t s ( 2 ) , the strong c h o l i n e r g i c d e f i c i e n c y in the septo-hippocampal pathway, the dwarf mutant e x h i b i t s , could be linked to i t s defect in memory a b i l i t y . REFERENCES I . Bouchon, R. and W i l l , B., Physiol. Behav., 28 (1982) 971. 2. Ebel, A. et a l . C.R. Acad. S c i . , 283 (1976) 535.
GENDER DIFFERENCES IN EXPLORATION AND NEOPHOBIA IN THE YOUNG RAT. EFFECT OF AN EARLY SEPTAL LESION ECLANCHER, F. AND ANGST, M.J. Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, 5, Rue Blaise Pascal, 67084 Strasbourg C#dex, France When placed in an open f i e l d at 20, 30, and 40 days of age, group-raised Wistar rats were found to d i s p l a y at 30 days a p a r t i c u l a r l y high level of responsiveness (ambulation and r e a r i n g s ) , with no d i f f e r e n c e between males and females. A septal l e s i o n performed at 6 days of age resulted in a c l e a r increase of the locomotor a c t i v i t y
already at 20 days of age. Gender d i f f e r e n c e s appeared in septal
r a t s , the females being more a c t i v e than the males at e i t h e r age, and the males rearing more often than the females at 30 days of age.
202
When the rats were given at 30 days the p o s s i b i l i t y
to choose between entering f r e e l y a novel
chamber or staying in the f a m i l i a r one, control rats showed neophobia (the males more than the f e males) while septal rats did not, whatever the gender of the animals. On the f i r s t t e s t , the locomotor a c t i v i t y
minute of the
displayed by septal rats in the f a m i l i a r chamber as well as in the no-
vel one was higher than that of control r a t s . This a c t i v i t y of control r a t s .
decreased afterwards to reach the l e v e l s
These r e s u l t s show that the septum is i n v o l v e d , at very early stages of the ontogenesis of the r a t , in the i n h i b i t o r y control over responsiveness to an unavoidable novel environment ( open f i e l d ) as well as in the induction of neophobia towards an avoidable one. But i t seems that t h i s limbic s t r u c t u r e does not intervene at an e a r l y age in the mediation of sexual hormone-induced d i f f e r e n t i a l modulation of r e a c t i v i t y
in the female and male young rats confronted to the open f i e l d .
DETECTION OF STATIONARY AND MOVING VISUAL PATTERNS IN THE PIGEON EMMERT, K.-H. Abteilung f u r Vergleichende Neurobiologie, U n i v e r s i t ~ t Ulm, D-7900 Ulm, Germany In a psychophysical experiment visual pattern detection of pigeons was analysed by means of the s i g n a l - d e t e c t i o n theory. Pigeons were trained to d i s c r i m i n a t e geometrical patterns ( p o s i t i v e stimulus: c i r c l e ;
negative
stimulus: rhomb) superimposed with Gaussian noise. During the experimental sessions the animals were free to move in the t e s t box. The number of correct choices was measured in r e l a t i o n to d i s t i n c t s i g n a l - t o - n o i s e r a t i o s (S/N), obtained by varying the signal i n t e n s i t y . From these data detection p r o b a b i l i t y (PD) was calculated as a f u n c t i o n of S/N. For analysis S/N at PD50 (75% correct choices) of each animal was applied. The performance f o r d i s c r i m i n a t i n g s t a t i o n a r y patterns reached PD50 at S/N - 1.6 (mean of e i g h t animals). This r e s u l t corresponds to that obtained in the cat when tested in the same s i t u a t i o n ( I ) . Pattern
movement is found to increase the performance only s l i g h t l y
contrast to mammals ( c a t : f a c t o r 4 . . 5 )
( f a c t o r 1 . 6 ) , which is in
(2); man: f a c t o r 10 (3).
The size of the pattern seems to have only a s l i g h t influence on the detection p r o b a b i l i t y . When the width of the patterns was altered by a f a c t o r of 0.29, S/N at reference PD was nearly unchanged in about 75% of the animals in e i t h e r case. To decide whether or not a signal was presented in the noise the pigeons needed lower S/N than they did f o r equivalent d i s c r i m i n a t i o n tasks ( s t a t i o n a r y pattern: f a c t o r 3.1, moving p a t t e r n : f a c t o r 4.3).
In a d d i t i o n , observations of the animals during the t e s t seem to i n d i c a t e that the pigeons
analysed the s t i m u l i with t h e i r A r e a e D o r s a l e s .Thus, the c o r r e l a t i o n of our psychphysical measurements with the behavioural observations support the hypothesis about f u n c t i o n a l properties of the Area d o r s a l i s proposed by Martinoya et a l .
(4).