- Email: [email protected]
126 Effect of K+ channel blocker, quinine, on terminal and dendritic dopamine release: In vivo microdialysis study
$25
126
EFFECT OF K* CHANNEL BLOCKER. QUININE. ON TERMINAL AND DENDRITIC DOPAMINE RELEASE: IN VIV0 MICRODIALYSISSTUDY TAK_AHIKOTANAKA. ~IASAMIYOSHIDA, IIIDEYASUYOKO0. KATSUIiIR0MIZOGUCHIAND MASATOSHITANAKA D_epartment of Pharmacology. Kurume University School of Medicine. Kurume830, Japan.
B r a i n m i c r o d i a l y s i s was used to examine t h e e f f e c t of i n t r a n i g r a l i n f u s i o n of potassium channel b l o c k e r , q u i n i n e (QIN}, on both t h e r a t s t r i a t a l and n i g r a l dopamine (DA) r e l e a s e in v i v o . QIN ~as a d m i n ~ t e r e d to t h e s u b s t a n t i a n i g r a t h r o u g h t h e d i a l y s i s membrane, whcreas the r e l e a s e of DA and 3 . 4 - d i h y d r o x y p h e n y l a c e t i c a c i d (DOPAC) were r e c o r d e d both in the s u b s t a n t i a n i g r a and i n t h e i p s i l a t e r a l striatum, l ~ t r a n i g r a l i n f u s i o n of QIN (1 mM) s i g n i f i c a n t l y d e c r e a s e d e x t r a c e l l u l a r c o n c e n t r a t i o n s of DA b o t h in the s u b s t a n t i a n i g r a and in the i p s i l a t e r a l s t r i a t u m . During t h e s e i n f u s i o n s e x t r a c e l l u l a r DOPAC l e v e l s a l s o d e c r e a s e d s i g n i f i c a n t l y in t h e b o t h a r e a s . In c o n t r a s t , l o c a l i n f u s i o n of QIN (10 - s . 1 0 - ' . 10 -~ M) i n t o t h e s t r i a t u m i n c r e a s e d e x t r a c e l l u l a r c o n c e n t r a t i o n s of DA in a d o s e - d e p e n d e n t manner. These r e s u l t s s u g g e s t t h a t potassium channel b l o c k e r , QIN, a f f e c t s endogenous DA r e l e a s e d i f f e r e n t i a l l y in the DAergic t e r m i n a l and d e n d r i t i c s i t e s .
127
MEMBRANE K + CURRENTS OF SYMPATIIETIC PREGANGLIONIC NEURONS IN NEONATAL RAT SPINAL CORD. TAKEFUMI MIYAZAKI~ HARUO KOBAYASHI AND TSUNEO TOSAKA. Dept. of Physiol. T Tokyo Medical Colleget Shinjuku-ku) Tokyo 160) Japan
S y m p a t h e t i c p r e g a n g l i o n i c n e u r o n s (SPNs) in n e o n a t a l rat spinal cord were i d e n t i f i e d by r e t r o g r a d e l a b e l i n g w i t h f l u o r e s c e n t dye Dil i n j e c t e d into the cervical ganglion at the P3 stage. First to third thoracic cords were dissected from P7 to PI4 rats and cut into slices (ca. 120 ~m thickness). In those slices SPNs were recognized at the lateral horn. We investigated by the whole-cell clamp technique on the membrane K + currents of the lateral horn neurons identified as SPNs at room temperature. Depolarizing command pulse from a holding potential of -72 mV induced the slow outward current at the levels more positive than -60 mV in the solution containing i ~ M tetrodotoxin (TTX). Tail current analysis revealed that this c u r r e n t was c a r r i e d by K +. The results in the s o l u t i o n c o n t a i n i n g 30 mM tetraethylammonium chloride or in the nominal CaZ+-free solution replaced by CoZ+ indicated that this slow outward K + current consisted of the CaZ+-dependent and the d e l a y e d r e c t i f i e r K + currents. In a d d i t i o n to these c u r r e n t s ) we found 4aminopyridine-sensitive transient outward current induced by depolarization from a h y p e r p o l a r i z i n g p r e p u l s e p o t e n t i a l ) C s + - s e n s i t i v e inward r e c t i f i e r c u r r e n t and another transient outward current following the TTX-sensitive Na + inward current which is suppressed in the Li + solution substituting for Na +.
128
DIFFERENTIAL EFFECTS OF ISCHEMIA-LIKE CONDITION ON CA1 PYRAMIDAL CELLS AND GRANULE CELLS IN RAT HIPPOCAMPAL SLICES. HITOSH! SHIMIZU, AKIRA MIZUGUCHI AND MAMORU AOKI, Dept. of Physiol., School of
_Medicine, Sapporo Medical University, Sapporo 060, Japan. The regional difference of responses to oxygen-glucose deprivation (Hypo/G(-)) was studied in CA1 pyramidal cells(PC) and granule cells(GC) of rat hippocampal slices. Changes of membrane potentials and antidromic action potentials(AAP) during Hypo/G(-) were compared between PCs and GCs by intracellular recordings. Intracellular calcium concentrations ([Ca2+]i) were measured using the fura-2 method. In PCs, Hypo/G(-),produced an intial hyperpolarization(~9mV) and a following rapid depolarization with disappearance of AAPs in about 7 to 11 min. By contrast, in GCs, Hypo/G(-) produced a gradu~ depolarization with a silght Intial hyperpolarization (~3mV), although the time of disappearance of AAPs was similar. Remarkable increase In [Ca2+]iwas observed at the rapid depolarization phase both in the CA1 area and the dentate gyrus, but the peak [Ca2+]iwas significantly higher in the CA1 area. After reox~,genation, Membrane potentials of GCs Showed better recovery than those of PCs. These results demonstrate the differential responses to Hypo/G(-) between PCs and GCs.
126
EFFECT OF K* CHANNEL BLOCKER. QUININE. ON TERMINAL AND DENDRITIC DOPAMINE RELEASE: IN VIV0 MICRODIALYSISSTUDY TAK_AHIKOTANAKA. ~IASAMIYOSHIDA, IIIDEYASUYOKO0. KATSUIiIR0MIZOGUCHIAND MASATOSHITANAKA D_epartment of Pharmacology. Kurume University School of Medicine. Kurume830, Japan.
B r a i n m i c r o d i a l y s i s was used to examine t h e e f f e c t of i n t r a n i g r a l i n f u s i o n of potassium channel b l o c k e r , q u i n i n e (QIN}, on both t h e r a t s t r i a t a l and n i g r a l dopamine (DA) r e l e a s e in v i v o . QIN ~as a d m i n ~ t e r e d to t h e s u b s t a n t i a n i g r a t h r o u g h t h e d i a l y s i s membrane, whcreas the r e l e a s e of DA and 3 . 4 - d i h y d r o x y p h e n y l a c e t i c a c i d (DOPAC) were r e c o r d e d both in the s u b s t a n t i a n i g r a and i n t h e i p s i l a t e r a l striatum, l ~ t r a n i g r a l i n f u s i o n of QIN (1 mM) s i g n i f i c a n t l y d e c r e a s e d e x t r a c e l l u l a r c o n c e n t r a t i o n s of DA b o t h in the s u b s t a n t i a n i g r a and in the i p s i l a t e r a l s t r i a t u m . During t h e s e i n f u s i o n s e x t r a c e l l u l a r DOPAC l e v e l s a l s o d e c r e a s e d s i g n i f i c a n t l y in t h e b o t h a r e a s . In c o n t r a s t , l o c a l i n f u s i o n of QIN (10 - s . 1 0 - ' . 10 -~ M) i n t o t h e s t r i a t u m i n c r e a s e d e x t r a c e l l u l a r c o n c e n t r a t i o n s of DA in a d o s e - d e p e n d e n t manner. These r e s u l t s s u g g e s t t h a t potassium channel b l o c k e r , QIN, a f f e c t s endogenous DA r e l e a s e d i f f e r e n t i a l l y in the DAergic t e r m i n a l and d e n d r i t i c s i t e s .
127
MEMBRANE K + CURRENTS OF SYMPATIIETIC PREGANGLIONIC NEURONS IN NEONATAL RAT SPINAL CORD. TAKEFUMI MIYAZAKI~ HARUO KOBAYASHI AND TSUNEO TOSAKA. Dept. of Physiol. T Tokyo Medical Colleget Shinjuku-ku) Tokyo 160) Japan
S y m p a t h e t i c p r e g a n g l i o n i c n e u r o n s (SPNs) in n e o n a t a l rat spinal cord were i d e n t i f i e d by r e t r o g r a d e l a b e l i n g w i t h f l u o r e s c e n t dye Dil i n j e c t e d into the cervical ganglion at the P3 stage. First to third thoracic cords were dissected from P7 to PI4 rats and cut into slices (ca. 120 ~m thickness). In those slices SPNs were recognized at the lateral horn. We investigated by the whole-cell clamp technique on the membrane K + currents of the lateral horn neurons identified as SPNs at room temperature. Depolarizing command pulse from a holding potential of -72 mV induced the slow outward current at the levels more positive than -60 mV in the solution containing i ~ M tetrodotoxin (TTX). Tail current analysis revealed that this c u r r e n t was c a r r i e d by K +. The results in the s o l u t i o n c o n t a i n i n g 30 mM tetraethylammonium chloride or in the nominal CaZ+-free solution replaced by CoZ+ indicated that this slow outward K + current consisted of the CaZ+-dependent and the d e l a y e d r e c t i f i e r K + currents. In a d d i t i o n to these c u r r e n t s ) we found 4aminopyridine-sensitive transient outward current induced by depolarization from a h y p e r p o l a r i z i n g p r e p u l s e p o t e n t i a l ) C s + - s e n s i t i v e inward r e c t i f i e r c u r r e n t and another transient outward current following the TTX-sensitive Na + inward current which is suppressed in the Li + solution substituting for Na +.
128
DIFFERENTIAL EFFECTS OF ISCHEMIA-LIKE CONDITION ON CA1 PYRAMIDAL CELLS AND GRANULE CELLS IN RAT HIPPOCAMPAL SLICES. HITOSH! SHIMIZU, AKIRA MIZUGUCHI AND MAMORU AOKI, Dept. of Physiol., School of
_Medicine, Sapporo Medical University, Sapporo 060, Japan. The regional difference of responses to oxygen-glucose deprivation (Hypo/G(-)) was studied in CA1 pyramidal cells(PC) and granule cells(GC) of rat hippocampal slices. Changes of membrane potentials and antidromic action potentials(AAP) during Hypo/G(-) were compared between PCs and GCs by intracellular recordings. Intracellular calcium concentrations ([Ca2+]i) were measured using the fura-2 method. In PCs, Hypo/G(-),produced an intial hyperpolarization(~9mV) and a following rapid depolarization with disappearance of AAPs in about 7 to 11 min. By contrast, in GCs, Hypo/G(-) produced a gradu~ depolarization with a silght Intial hyperpolarization (~3mV), although the time of disappearance of AAPs was similar. Remarkable increase In [Ca2+]iwas observed at the rapid depolarization phase both in the CA1 area and the dentate gyrus, but the peak [Ca2+]iwas significantly higher in the CA1 area. After reox~,genation, Membrane potentials of GCs Showed better recovery than those of PCs. These results demonstrate the differential responses to Hypo/G(-) between PCs and GCs.