The optic tectum of the salmon:site of interaction of neurohormonal photoperiodic and neural visual signals. The GABAergic neuronal system and melatonin receptors.
(1998)- Abstract
- Melatonin is a neurohormone which mediates photoperiodic signals from the pineal organ to the brain. GABA (g-aminobutyric acid) is the major inhibitory transmitter in the central nervous system. It has previously been suggested that functional interaction exists between central binding sites for GABA/benzodiazepines (GABAA/bzd receptors) and melatonin in the central nervous system, and that GABA and benzodiazepines may be involved in circadian responses to light. To investigate if there is a structural basis for interactions between the neurohormone melatonin and GABA in the primary visual center, the optic tectum of the brain of the Atlantic salmon (Salmo salar) I compared the distribution of the GABAA/benzodiazepine receptor... (More)
- Melatonin is a neurohormone which mediates photoperiodic signals from the pineal organ to the brain. GABA (g-aminobutyric acid) is the major inhibitory transmitter in the central nervous system. It has previously been suggested that functional interaction exists between central binding sites for GABA/benzodiazepines (GABAA/bzd receptors) and melatonin in the central nervous system, and that GABA and benzodiazepines may be involved in circadian responses to light. To investigate if there is a structural basis for interactions between the neurohormone melatonin and GABA in the primary visual center, the optic tectum of the brain of the Atlantic salmon (Salmo salar) I compared the distribution of the GABAA/benzodiazepine receptor complex(GABAA/bzd receptor) to that of melatonin receptors, using immunohistochemistry (for GABAA/bzd receptors) and quantitative autoradiography (for melatonin receptors). I also investigated if there is any difference in the binding of 2-[125I]iodomelatonin at day compared to at night. I was also interested to know which transmitter substance that mediates the light-/dark message from the retina to the optic tectum via the optic tract. By using immunohistochemistry I studied the distribution of GABA in the retina and in the optic tectum. The ganglion cells in the retina showed no GABA immunoreactivity indicating that GABA is not the transmitter mediating the light-/dark message to the optic tectum. An overlap in the distribution of GABAA/bzd receptors, melatonin receptors, and GABAergic neurons and fibers in the retinorecipient layers of the optic tectum was observed. Thus, there is a structural basis for interactions between GABA and melatonin in the optic tectum of the Atlantic salmon. It is likely that GABA is involved in the intrinsic processing of the light-/dark message in the optic tectum. The 2-[125I]iodomelatonin was found to be specific, saturable, displaceable and of high affinity, with a dissociation constant (Kd) 85±14 pM and a maximum number of binding sites (Bmax) 58±7 fmol/mg protein. The Hill plot coefficient (nH) was 2.0 which indicates the presence of two types of binding sites. The presence of two binding sites could, however, not be statistically verified using MACLIGAND. No significant differences were found when comparing the 2-[125I]iodomelatonin at night to that at day. (Less)
- Abstract (Swedish)
- Popular Abstract in Swedish
Melatonin är ett hormon som produceras i, och frisätts från pinealorganet hos ryggradsdjur. Melatoninets viktigaste uppgift är att till hjärnan förmedla signalen om nattens längd, d.v.s vilken årstid det är. Produktionen och frisläppningen sker rytmiskt med den högsta nivån under natten. Melatoninet transporteras ut i kroppen via blodet och binder till särskilda mottagarstrukturer, (receptorer) i hjärnan. Tidigare undersökningar tyder på att mealtonin och GABA interagerar med varandra d.v.s kan fästa på samma typ av receptor. GABA, (gamma-aminobutyric acid) är den vanligaste inhibitoriska transmittorsubstansen i centrala nervsystemet hos alla ryggradsdjur. Jag har studerat och jämfört... (More) - Popular Abstract in Swedish
Melatonin är ett hormon som produceras i, och frisätts från pinealorganet hos ryggradsdjur. Melatoninets viktigaste uppgift är att till hjärnan förmedla signalen om nattens längd, d.v.s vilken årstid det är. Produktionen och frisläppningen sker rytmiskt med den högsta nivån under natten. Melatoninet transporteras ut i kroppen via blodet och binder till särskilda mottagarstrukturer, (receptorer) i hjärnan. Tidigare undersökningar tyder på att mealtonin och GABA interagerar med varandra d.v.s kan fästa på samma typ av receptor. GABA, (gamma-aminobutyric acid) är den vanligaste inhibitoriska transmittorsubstansen i centrala nervsystemet hos alla ryggradsdjur. Jag har studerat och jämfört utbredningen av melatonin receptorer, GABA receptorer och GABA i laxhjärnan och GABA i näthinnan för att i tectum opticum (primärt syncentrum i laxhjärnan) finna en strukturell bas för interaktioner mellan melatonin och GABA, samt för att undersöka om GABA är den transmittorsubstans som skickar budskap om ljus-/mörker via synnerven till tectum opticum. För att göra detta har jag använt mig av två olika metoder, immunohistokemi och autoradiografi. I immunohistokemi använder man sig av antikroppar mot substansen man vill lokalisera, i mitt fall GABA och en typ av GABA receptor. Vid lokaliseringen av melatoninreceptorer använde jag mig av autoradiografi. I denna metod använder man radioaktivt märkt melatonin som binder till receptorerna i vävnaden, en röntgenfilm läggs på de inmärkta snitten och de områden där det radioaktiva melatoninet är lokaliserat svärtar filmen. Celler i näthinnan med förbindelser till tectum opticum (ganglioncellerna) visade sig inte innehålla GABA. Det är därför int e troligt att denna substans förmedlar ljus-/mörker budskapet från näthinnan till tectum opticum. Däremot visar resultaten att det finns en möjlig strukturell bas för inbindning av både GABA och melatonin i tectum opticum, då utbredingen av melatoninreceptorer och GABAreceptorer visar en påtaglig överlappning. Detta betyder att dessa två substanser kan samverka i behandlingen av dagslängdsbudskapet inom tectum opticum och vidarebefordrandet av detta till andra delar av hjärnan. Jag undersökte också om det är någon skillnad i mängden melatonin som binder in på natten jämfört med på dagen. Mina resultat visar inga signifikanta skillnader vid de olika tidpunkterna. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/38910
- author
- Anzelius, Marie LU
- supervisor
- opponent
-
- Dr Meissl, Hilmar, Max-Planck Institut für physiologische und klinische Forschung, Bad Nauheim, Tyskland
- organization
- publishing date
- 1998
- type
- Thesis
- publication status
- published
- subject
- keywords
- Animal anatomy, melatonin receptors, GABA, optic tectum, fish, brain, animal morphology, Djurs anatomi och morfologi
- pages
- 95 pages
- publisher
- Department of Zoology, Lund University
- defense location
- Högtidssalen Zoologiska inst
- defense date
- 1998-06-09 10:00:00
- external identifiers
-
- other:ISRN: LUNBDS/NBZS--98/1029--SE
- language
- English
- LU publication?
- yes
- additional info
- The information about affiliations in this record was updated in December 2015. The record was previously connected to the following departments: Zoology (Closed 2011) (011012000)
- id
- da29c6fb-87a4-4f90-91c5-23c490a0903d (old id 38910)
- date added to LUP
- 2016-04-04 10:07:50
- date last changed
- 2018-11-21 20:56:56
@phdthesis{da29c6fb-87a4-4f90-91c5-23c490a0903d,
abstract = {{Melatonin is a neurohormone which mediates photoperiodic signals from the pineal organ to the brain. GABA (g-aminobutyric acid) is the major inhibitory transmitter in the central nervous system. It has previously been suggested that functional interaction exists between central binding sites for GABA/benzodiazepines (GABAA/bzd receptors) and melatonin in the central nervous system, and that GABA and benzodiazepines may be involved in circadian responses to light. To investigate if there is a structural basis for interactions between the neurohormone melatonin and GABA in the primary visual center, the optic tectum of the brain of the Atlantic salmon (Salmo salar) I compared the distribution of the GABAA/benzodiazepine receptor complex(GABAA/bzd receptor) to that of melatonin receptors, using immunohistochemistry (for GABAA/bzd receptors) and quantitative autoradiography (for melatonin receptors). I also investigated if there is any difference in the binding of 2-[125I]iodomelatonin at day compared to at night. I was also interested to know which transmitter substance that mediates the light-/dark message from the retina to the optic tectum via the optic tract. By using immunohistochemistry I studied the distribution of GABA in the retina and in the optic tectum. The ganglion cells in the retina showed no GABA immunoreactivity indicating that GABA is not the transmitter mediating the light-/dark message to the optic tectum. An overlap in the distribution of GABAA/bzd receptors, melatonin receptors, and GABAergic neurons and fibers in the retinorecipient layers of the optic tectum was observed. Thus, there is a structural basis for interactions between GABA and melatonin in the optic tectum of the Atlantic salmon. It is likely that GABA is involved in the intrinsic processing of the light-/dark message in the optic tectum. The 2-[125I]iodomelatonin was found to be specific, saturable, displaceable and of high affinity, with a dissociation constant (Kd) 85±14 pM and a maximum number of binding sites (Bmax) 58±7 fmol/mg protein. The Hill plot coefficient (nH) was 2.0 which indicates the presence of two types of binding sites. The presence of two binding sites could, however, not be statistically verified using MACLIGAND. No significant differences were found when comparing the 2-[125I]iodomelatonin at night to that at day.}},
author = {{Anzelius, Marie}},
keywords = {{Animal anatomy; melatonin receptors; GABA; optic tectum; fish; brain; animal morphology; Djurs anatomi och morfologi}},
language = {{eng}},
publisher = {{Department of Zoology, Lund University}},
school = {{Lund University}},
title = {{The optic tectum of the salmon:site of interaction of neurohormonal photoperiodic and neural visual signals. The GABAergic neuronal system and melatonin receptors.}},
year = {{1998}},
}