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Suppression of transcription of inward-rectifier K+ channel by neural induction in ascidian embryos
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SUPPRESSION OF TRANSCRIPTION OF INWARD-RECTIFIER K+ CHANNEL BY NEURAL INDUCTION IN ASCIDIAN EMBRYOS.
YASUSHI OKAMURA*. AND KUNITARO TAKAHASHI. Denartment of Neurobiolo~,y,
Institute of Brain Research. Facultv of Medicine. Universitv of Tokyo. 7-3-1 Hon2o. Bunkvo-ku. Tokyo 113. Janan. In a protochordate, Halocynthia aurantium, protease treatment (subtilisin 0.1%, 30 rain) during the period corresponding to the 64-cell stage can induce neural-type differentiation in a cleavage-arrested ectodermal blastomere, a4-2, isolated from the eight-cell embryo, which consistently differentiates into the epidermal-type cell without treatment (Okado & Takahashi, in the press). In the present study, the membrane excitability was compared between protease-treated (induced) and non-treated (non-induced) cells at earlier stages of development with the two-electrode vohage clamp technique. At the stage corresponding to the late gastrula, the current density of the inward-rectifier K+ channel markedly increased in the noninduced cell, while in the induced cell the density was less than one third of that in the non-induced cell. By injecting 0~amanitin, a highly specific transcription inhibitor, the transcription for the inward-rectifier K÷ channel in both cells was found to have already started before protease treatment. Furthermore, in the induced cell, the injection of a-amanitin after protease treatment did not affect the expression of the inward-rectifier K÷ channel. These results suggest that neural induction suppressed the transcription for the inward-rectifier K+ channel which had already been initiated before the 64-cell stage.
P O S T N A T A L D E V E L O P M E N T OF E L E C T R I C A L A C T I V I T Y OF RAT N I G R O S T R I A T A L NEURONS. JAMES M. TEPPER*, F R A N C I N E TRENT*, SHOJI NAKAMURA**, Center for M o l e c u l a r and B e h a v - ~ r a l N e u r o s c l e n o e and D e p a r t m e n t of B i o l o g i c a l Sciences, Rutgers, The State U n i v e r s i t y of New Jersey, U.S.A. and * * D e p a r t m e n t of Physiology, K a n a z a w a University, F a c u l t y of Medicine, K a n a z a w a 920, Japan. The e l e c t r i c a l a c t i v i t y of n i g r o s t r i a t a l d o p a m i n e r g l c (NSDA) n e u r o n s w a s r e c o r d e d e x t r a - and i n t r a c e l l u l a r l y in u r e t h a n e - a n e s t h e t i z e d (1.3 mg/g, i.p.) rat p u p s d u r i n g e a r l y stages of d e v e l o p m e n t from p o s t n a t a l day (PD) i to PD28. The single-unit a c t i v i t y of NSDA n e u r o n s w a s i d e n t i f i e d by a n t i d r o m l c r e s p o n s e s to striatal s t i m u l a t i o n as well as h i s t o l o g i c a l v e r i f i c a t i o n of the s t i m u l a t i n g and r e c o r d i n g sites. NSDA n e u r o n s from PDI-3 rats fired s p o n t a n e o u s l y at low rates ( a p p r o x i m a t e l y I spike/sec), in an irregular p a t t e r n l a c k i n g bursts, w i t h long p e r i o d s of silence. S p o n t a n e o u s firing rates increased and b e c a m e more regular w i t h age, and by the fourth p o s t n a t a l week, firing rate and p a t t e r n r e a c h e d the adult level. M e a n a n t i d r o m i c latency w a s n e a r l y the same from neonatal p e r i o d to adult, a l t h o u g h the p r o p o r t i o n of a n t i d r o m i c r e s p o n s e s s h o w i n g the full IS-SD spike d e c r e a s e d w i t h age. Strlatal s t i m u l a t i o n p r i n c i p a l l y induced an i n h i b i t i o n w h o s e d u r a t i o n w a s r e d u c e d from PDI t h r o u g h adulthood. I n t r a c e l l u l a r r e c o r d i n g s from NSDA n e u r o n s did not reveal s t r i a t a l - e v o k e d synaptic responses. These r e s u l t s indicate that a l t h o u g h NSDA n e u r o n s are f u c t i o n a l l y a c t i v e e v e n at birth, some e l e c t r o p h y s i o l o g i c a l p r o p e r t i e s r e m a i n immature.
DEVELOPMENTAL CHANGES OF PARVALBUMIN-IMMUNOREACTIVITY IN THE BRAIN. AKIKQ SETQ-OHSHIMA *I, EIKO AOK1.2, REIJI SEMBA2. CLAUS. W. HEIZMANN*3~ Departments of IMorpholouy and 2perinatolo~y. Institute for Develoomental Research. Alahi Prefectural Cnlnny: Kasu~at: Ataht 480-03_ lanan. 3Denartment of Pediatrics. Division of Clinical Chemistry. University of Z'drich. 8032 Z'drlch. Switzerland. Parvalbumin is present in a distinct subpopulation of neurons in the brain. We followed developmental changes in the distribution of parvalbumin-lmmunoreactivity (PVI) in the brain of rat and Mongolian gerbil. Animals were perfased after anesthesia with chloral hydrate. Freezing microtome-sections (35-50 urn-thick) were treated for immunohistochemistry. At early stages of development, PVI was only localized in restricted areas such as several fiber systems in the hindbrain and neurons of the nuc. mesencephalic trigemini. After birth, PVl-positive cells increased but the date of appearance varied by area. Within the cerebral cortex, parietal cortex showed PVI-positlve cells earlier than temporal cortex. Neurons of several areas such as the cerebral cortex, corpus striatum, hippocampus and the nuc. pretectalis and Purkinje ceils in the cerebellum gained PVI later, after postnatal day 7. In the central auditory system of gerbil, the dates of PVI appearance in .each nucleus corresponded with those of 2-deoxyglucose uptake increase to sounds reported by Ryan et al.lD, which suggested the close temporal correlation between functional maturation and PVI appearance in this system. In gerbil brain, PVI-positive fibers with less GABA-IIke immunoreactlvity were observed in the cerebral cortex and hippocampas, in addition to a population of PVI-posidve neurons similar to those in the at. They seemed to resemble fibers which were found in rat brain only in the early postnatal days. I)Exp. Brain Res. 47 (1982) 428-436.
SUPPRESSION OF TRANSCRIPTION OF INWARD-RECTIFIER K+ CHANNEL BY NEURAL INDUCTION IN ASCIDIAN EMBRYOS.
YASUSHI OKAMURA*. AND KUNITARO TAKAHASHI. Denartment of Neurobiolo~,y,
Institute of Brain Research. Facultv of Medicine. Universitv of Tokyo. 7-3-1 Hon2o. Bunkvo-ku. Tokyo 113. Janan. In a protochordate, Halocynthia aurantium, protease treatment (subtilisin 0.1%, 30 rain) during the period corresponding to the 64-cell stage can induce neural-type differentiation in a cleavage-arrested ectodermal blastomere, a4-2, isolated from the eight-cell embryo, which consistently differentiates into the epidermal-type cell without treatment (Okado & Takahashi, in the press). In the present study, the membrane excitability was compared between protease-treated (induced) and non-treated (non-induced) cells at earlier stages of development with the two-electrode vohage clamp technique. At the stage corresponding to the late gastrula, the current density of the inward-rectifier K+ channel markedly increased in the noninduced cell, while in the induced cell the density was less than one third of that in the non-induced cell. By injecting 0~amanitin, a highly specific transcription inhibitor, the transcription for the inward-rectifier K÷ channel in both cells was found to have already started before protease treatment. Furthermore, in the induced cell, the injection of a-amanitin after protease treatment did not affect the expression of the inward-rectifier K÷ channel. These results suggest that neural induction suppressed the transcription for the inward-rectifier K+ channel which had already been initiated before the 64-cell stage.
P O S T N A T A L D E V E L O P M E N T OF E L E C T R I C A L A C T I V I T Y OF RAT N I G R O S T R I A T A L NEURONS. JAMES M. TEPPER*, F R A N C I N E TRENT*, SHOJI NAKAMURA**, Center for M o l e c u l a r and B e h a v - ~ r a l N e u r o s c l e n o e and D e p a r t m e n t of B i o l o g i c a l Sciences, Rutgers, The State U n i v e r s i t y of New Jersey, U.S.A. and * * D e p a r t m e n t of Physiology, K a n a z a w a University, F a c u l t y of Medicine, K a n a z a w a 920, Japan. The e l e c t r i c a l a c t i v i t y of n i g r o s t r i a t a l d o p a m i n e r g l c (NSDA) n e u r o n s w a s r e c o r d e d e x t r a - and i n t r a c e l l u l a r l y in u r e t h a n e - a n e s t h e t i z e d (1.3 mg/g, i.p.) rat p u p s d u r i n g e a r l y stages of d e v e l o p m e n t from p o s t n a t a l day (PD) i to PD28. The single-unit a c t i v i t y of NSDA n e u r o n s w a s i d e n t i f i e d by a n t i d r o m l c r e s p o n s e s to striatal s t i m u l a t i o n as well as h i s t o l o g i c a l v e r i f i c a t i o n of the s t i m u l a t i n g and r e c o r d i n g sites. NSDA n e u r o n s from PDI-3 rats fired s p o n t a n e o u s l y at low rates ( a p p r o x i m a t e l y I spike/sec), in an irregular p a t t e r n l a c k i n g bursts, w i t h long p e r i o d s of silence. S p o n t a n e o u s firing rates increased and b e c a m e more regular w i t h age, and by the fourth p o s t n a t a l week, firing rate and p a t t e r n r e a c h e d the adult level. M e a n a n t i d r o m i c latency w a s n e a r l y the same from neonatal p e r i o d to adult, a l t h o u g h the p r o p o r t i o n of a n t i d r o m i c r e s p o n s e s s h o w i n g the full IS-SD spike d e c r e a s e d w i t h age. Strlatal s t i m u l a t i o n p r i n c i p a l l y induced an i n h i b i t i o n w h o s e d u r a t i o n w a s r e d u c e d from PDI t h r o u g h adulthood. I n t r a c e l l u l a r r e c o r d i n g s from NSDA n e u r o n s did not reveal s t r i a t a l - e v o k e d synaptic responses. These r e s u l t s indicate that a l t h o u g h NSDA n e u r o n s are f u c t i o n a l l y a c t i v e e v e n at birth, some e l e c t r o p h y s i o l o g i c a l p r o p e r t i e s r e m a i n immature.
DEVELOPMENTAL CHANGES OF PARVALBUMIN-IMMUNOREACTIVITY IN THE BRAIN. AKIKQ SETQ-OHSHIMA *I, EIKO AOK1.2, REIJI SEMBA2. CLAUS. W. HEIZMANN*3~ Departments of IMorpholouy and 2perinatolo~y. Institute for Develoomental Research. Alahi Prefectural Cnlnny: Kasu~at: Ataht 480-03_ lanan. 3Denartment of Pediatrics. Division of Clinical Chemistry. University of Z'drich. 8032 Z'drlch. Switzerland. Parvalbumin is present in a distinct subpopulation of neurons in the brain. We followed developmental changes in the distribution of parvalbumin-lmmunoreactivity (PVI) in the brain of rat and Mongolian gerbil. Animals were perfased after anesthesia with chloral hydrate. Freezing microtome-sections (35-50 urn-thick) were treated for immunohistochemistry. At early stages of development, PVI was only localized in restricted areas such as several fiber systems in the hindbrain and neurons of the nuc. mesencephalic trigemini. After birth, PVl-positive cells increased but the date of appearance varied by area. Within the cerebral cortex, parietal cortex showed PVI-positlve cells earlier than temporal cortex. Neurons of several areas such as the cerebral cortex, corpus striatum, hippocampus and the nuc. pretectalis and Purkinje ceils in the cerebellum gained PVI later, after postnatal day 7. In the central auditory system of gerbil, the dates of PVI appearance in .each nucleus corresponded with those of 2-deoxyglucose uptake increase to sounds reported by Ryan et al.lD, which suggested the close temporal correlation between functional maturation and PVI appearance in this system. In gerbil brain, PVI-positive fibers with less GABA-IIke immunoreactlvity were observed in the cerebral cortex and hippocampas, in addition to a population of PVI-posidve neurons similar to those in the at. They seemed to resemble fibers which were found in rat brain only in the early postnatal days. I)Exp. Brain Res. 47 (1982) 428-436.