Exploration in Acomyis cahirinus and Mus musculus (Rodentia)

170

We investigated the acute e f f e c t of prenatal administration of pethidine on the rat f e t a l brain cAMP levels and ODC a c t i v i t y . Pregnant rats were exposed to a single dose of pethidine (50 mg/kg body weight) on day 20th of the gestation. A f t e r d i f f e r e n t time i n t e r v a l s f o l l o w i n g the i n j e c t i o n , the pregnant rats were s a c r i f i e d , the fetuses were removed and t h e i r brain extracted f o r cAMP levels and ODC a c t i v i t y determination. T h i r t y minutes a f t e r the pethidine a d m i n i s t r a t i o n , we observed a decrease in cAMP l e vel and ODC a c t i v i t y which reaches i t s maximum a f t e r two and three hours respect i v e l y . At three and four hours a f t e r the i n j e c t i o n , the cAMP levels and ODC activity

increase above the control l e v e l s .

Increase in ODC a c t i v i t y ,

generally corresponds to growth, regeneration or

repair processes. I t is very l i k e l y that the increase in ODC a c t i v i t y

several

hours a f t e r pethidine a d m i n i s t r a t i o n , is a r e s u l t of a repair process. Our data suggest that pethidine causes temporary a l t e r a t i o n s in cAMP levels and ODC a c t i v i t y

in the f e t a l brain. At t h i s stage, i t is d i f f i c u l t

to evaluate

the pharmacological s i g n i f i c a n c e of these t r a n s i t o r y changes. Further conclusions w i l l have to await more extensive studies.

EXPLORATION IN ACOMYIS CAHIRINUS AND MUS MUSCULUS (RODENTIA) BIRKE, L . I . * .

D'UDINE, B.** AND ALBONETTI, M.E.***

* The Open U n i v e r s i t y , Walton H a l l , Milton Keynes MK7 6AA, United Kingdom **Istituto

di Psicobiologia e Psicofarmacologia del C.N.R., Rome, I t a l y

***Scuola Normale Superiore. P.za dei Cavalieri I , 59100 Pisa, I t a l y The exploFatory behaviour of two species ofmurid rodents was compared in four experiments, designed to test predictions made on the basis of habitat d i f ferences between the two species in the w i l d . In the f i r s t

experiment, the res-

ponses of the two species to a novel area were studied: Mus was found to be more t e n t a t i v e , and to spend more time in the r e l a t i v e l y f a m i l i a r or safer start-box than Acomys. Mus appear to explore in the open arena by using frequent s h i f t s of a t t e n t i o n , whereas the r e s u l t s suggest that Acomys may persevere longer in exploring p a r t i c u l a r areas. Experiment two investigated responses to the addition of a small novel object. Although the species did respond d i f f e r e n t l y ,

the

major species differences were as in experiment one, and seemed to be related to the open arena rather than the object.

171

Since Mus, but not Acomys, use burrows, i t was predicted that they would use one more i f available in an open f i e l d . This was tested in two further experiments. I t was found that Acomys treated the available a r t i f i c i a l burrow as another novel object: Mus, as predicted, spent more time inside i t then Acomys. Experiment four investigated burrow use when a model predator was introduced: both species increased t h e i r use of the burrow but some species' differences were found. Mus ... responded to the model more by freezing, or running immediately into the burrow; Acomys responded more by fleeing.

ONTOGENETIC DEVELOPMENTOF SENSORY AND SONG CONTROL AREAS IN THE ZEBRA FINCH BRAIN BISCHOF, H.-J. AND HERRMANN, K. Lehrstuhl f u r Verhaltensphysiologie, U n i v e r s i t ~ t B i e l e f e l d , Postfach 8640, 4800 B i e l e f e l d I , FRG Sexual imprinting and song learning in birds are r e s t r i c t e d to a s e n s i t i v e period in early development. Therefore, i t might be possibTe that the storage of information from the environment, as i t occurs in these paradigms, is coupled to processes of development and d i f f e r e n t i a t i o n of the nervous system. To support t h i s assumption we recorded developmental a l t e r a t i o n s of the structure of the Zebra Finch brain and t r i e d to correlate these a l t e r a t i o n s to the wellknown behavioral data. The parameters under i n v e s t i g a t i o n were: a. Development of neuron size in d i f f e r e n t n u c l e i ; b. Development of n e u r o f i b r i l s (as i n d i c a t o r f o r growing f u n c t i o n a l i t y of nerves); c. Increase of myelinisation as i n d i c a t o r f o r decreasing p l a s t i c potency of neurons. From our data, the r e s u l t s of visual sensory areas and nuclei of the song control system are presented. The fasted development can be detected in nucleus rotundus, the diencephalic s t a t i o n of the tectofugal pathway. Cell sizes are at t h e i r maximum at 20 days from hatching, n e u r o f i b r i l s are a d u l t - l i k e at the same age, m y e l i n i s a t i o n is a d u l t - l i k e at 40 days. Cell size in the ectostriatum, the telencephalic area of the tectofugal pathway is at i t s maximum by 20 days too, development of n e u r o f i b r i l s and myelin is a d u l t - l i k e at 40 days. The development of two song control n u c l e i , the RA (n. robustus a r c h i s t r i a talis)

and HVC (Hyperstriatum ventrale pars caudalis) is somewhat delayed i f

compared with the visual n u c l e i . In HVC, neuron size is maximal with 40 days,