Dopaminergic control of self-stimulation

Dopaminergic control of self-stimulation

193 r a t e , blood pressure and magnitude estimation of pain were recorded p e r i o d i c a l l y throughout the sessions. Pain appeared a f t e r ...

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r a t e , blood pressure and magnitude estimation of pain were recorded p e r i o d i c a l l y throughout the sessions. Pain appeared a f t e r a mean delay of 14 ± 7 s (E.S.) then the votes increased l i n e a r l y with time. The t o l e r a t e d duration of pain increased with increasing salary and was l i n e a r l y related to the logarithm of the reward thus showing a decreasing u t i l i t y

of money when p i t t e d against pain.

DOPAMINERGIC CONTROL OF SELF-STIMULATION CAREY, R.J. VAMC at Syracuse, New York 13210, U.S.A. I n t e r f e r e n c e with brain dopamine neurotransmission can severely impair brain s t i m u l a t i o n reward behavior. The s i g n i f i c a n c e of t h i s impairment in reward behavior, however, has been a problematic issue. That i s , i t has been d i f f i c u l t

to decide whether the dopamine dysfunction has attenuated the

reward e f f e c t of the s t i m u l a t i o n or has merely rendered the animal less able to generate the behavi o r required to obtain reinforcement. To experimentally re-assess t h i s issue,the present studies examine the e f f e c t of n e u r o l e p t i c drugs and u n i l a t e r a l 6-hydroxydopamine lesions of f o r e b r a i n dopamine neurons on brain s t i m u l a t i o n reward in animals. In general, these studies h i g h l i g h t the subs t a n t i a l motoric d e f i c i t s

produced by the drug or l e s i o n treatments. By combining both treatments,

however, i t appeared that e f f e c t s on reward could be detected. S p e c i f i c a l l y , r a t s with b i l a t e r a l med i a l f o r e b r a i n bundle electrodes which generated comparable r a t e - i n t e n s i t y f u n c t i o n s f o r s e l f - s t i m u l a t i o n were adminstered u n i l a t e r a l

i n j e c t i o n s of 6-OHDA(4 ~I o f a 3 ~ I / N l

nigra and ventral tegmental area. I n i t i a l l y , was manifested by a d r a s t i c b i l a t e r a l two-month

sol.)

i n t o the substantia

the e f f e c t o f the severe u n i l a t e r a l dopamine depletion

decrease in s e l f - s t i m u l a t i o n which g r a d u a l l y recovered over a

period. When e q u i v a l e n t performance was re-established in each hemisphere electrode s i t e

the rats were given e i t h e r 0.1 mg/kg haloperidol or 3.0 mg/kg clozapine. In every case, s e l f - s t i m u l a t i o n was sharply reduced in the dopamine d e f i c i e n t hemisphere but unaffected or enhanced in the dopamine i n t a c t hemisphere. Since t h i s paradigm allowed each r a t to serve as i t s own control the l a t e r a l i z e d suppression in reward behavior could not be a t t r i b u t e d to a motoric d e f i c i t .

Thus, the com-

bined treatment of n e u r o l e p t i c drug and u n i l a t e r a l 6-hydroxydopamine l e s i o n provides a powerful technique to demonstrate t h a t dopamine has an important role in the reward aspect of brain s t i m u l a t i o n reward behavior.

ESCAPE INDUCED BY MICROINJECTIONS OF d-TUBOCURARINE INTO THE RAT'S MEDIAL HYPOTHALAMUSOR PERIAQUEDUCTAL GRAY: CHOLINERGIC OR GABAERGIC MEDIATION? CARRIVE, P., BRANDAO,M.,MOREAU, J.L. AND SCHMITT, P. Laboratoire de Neurophysiologie, Centre de Neurochimie du CNRS, 5, rue Blaise Pascal, 67084 Strasbourg, France