Laboratory of Chronobiology, Department of Science and Technology, National University of Quilmes, Buenos Aires, Argentina. Algo de ritmos circadianos,

Laboratory of Chronobiology, Department of Science and Laboratory of Chronobiology, Department of Science and Technology, National University of Quilmes, Buenos Aires, Technology, National University of Quilmes, Buenos Aires,

Argentina.Argentina.

Algo de ritmos circadianos, de avances de fase inducidos por luz y de resincronización

Una intro a lo que hacemos con el SCN, con el cGMP, el NO, PKG y la PDE, sin hablar de MAP, ni CRE, CREB, TNF,y menos de tve, BBC, CNN, FOX,

BBVA, y bla bla bla.

Los ritmos ocurren en todos los niveles de organización

INTRODUCCIINTRODUCCIONON

QUIMICO

Expresión génica, actividad eléctrica, síntesis y liberación de neurotransmisores.

CELULAR

FISIOLÓGICO Temperatura, presión arterial, frecuencia cardíaca, niveles de hormonas en sangre.

CONDUCTUAL

Conducta alimentaria, ciclo sueño/vigilia, actividad locomotora.

CELULAR FISIOLOGICO

POBLACIONALCONDUCTUAL

Propiedades Generales de los ritmos

• AMPLITUD

• FASE

• PERIODO

PARAMETEROS PERIOD PHASE SHIFT

La Cronobioloia Estudia los Ritmos Bilogicos

AMPLITUDE

TIME

Espectro de los Ritmos Biológicos

Rhythm Period Example0,1 sec electroencephalogram1 sec electrocardiogram6 sec breathing rhythm

60 min pulsatile hormone secretion90 min sleep staging

sleep - wake cyclebody temperature

28 days menstrual cycle365 days hibernation

Ultradian

Circadian

Infradian

24 hours

En mamíferos, el reloj biológico se halla en los núcleos supraquiasmaticos (SCN)

Output rhythms

Behavior

light

Suprachiasmatic Nucleus (SCN)

CARACTERISTICASNEUROQUIMICAS

EXPRESION GENES RELOJ

VIP PEPTIDO VASOACTIVO INTESTINAL

AVP VASOPRESINA

Región dorsomedialEXPRESION RITMICA

Región ventrolateralEXPRESION INDUCIDA POR LUZ

NSQ

QO

Los núcleos supraquiasmáticos (NSQ) son la sede del reloj biológico en mamíferos

3V: TERCER VENTRICULO

QO: QUIASMA OPTICO

INTRODUCCIINTRODUCCIONON

Calb: Calbindina

Ciclo LUZ-OSCURIDAD

INPUT

OSCILADOR

TEMPERATURA

NIVELES HORMONALES

EXPRESION DE PROTEINAS

ACTIVIDADLOCOMOTORAETC.

OUTPUT

Principales componentes del Sistema Circadiano

ZEITGEBER(exógeno)

oscilador (endógeno)

Sincronización Acoplamiento

Mecanismo de oscilación: el reloj molecular

CITOPLASMA

NUCLEO

CKI

CRYPER

PER

Degradación víaproteosoma

Per

Cry

Rev

otros

Genes blancoE-box

CLO

CK

BM

AL

CRYPER

CRY

PER

INTRODUCCIINTRODUCCIONON

L:D (14:10) vs D:D

Subjective DaySubjective Night

Hours 240

Light pulse

Phase advance

Light pulse

Phase delay

Subjective NightSubjective Day

Subjective DaySubjective Night

Hours 240

Light pulse

Phase advance

Light pulse

Phase delay

Subjective NightSubjective Day

Phase response curve (PRC) (PRC)

Ca2+

CaMKII

Ca2+-Calmodulin

Glu

Ca2+

NMDA-R

Light

CaMKII has been implicated in the resetting of the circadian clock by light exposure (Golombek and Ralph, 1994)

Signal transduction pathways responsible of photic mammalian phase advances

Ca2+

CaMKII

Ca2+-Calmodulin

NOS

Glu

Ca2+

NMDA-R

Light

A role for nNOS in circadian responses to light has been indicated by several pharmacological and electrophysiological studies (Melo et al., 1997)

Ca2+

CaMKII

Ca2+-Calmodulin

NOS

NOS

Glu

Ca2+

NMDA-R

Light

There is a direct pathway between CaMKII and NOS in the SCN (Agostino et al, 2004, Neurochem Int 44: 617-625)

CaMKII

Ca2+-Calmodulin

Ca2+

NOS

PKG

GC

Glu

Ca2+

NMDA-R

Light

An involvement for the NOS-GC-PKG pathway in light-induced phase advances has been indicated by several studies.

- cGMP induces phase advances in vitro (Prosser y Gillette, 1996)

- PKG inhibition blocks light-induced phase advances in vivo (Mathur et al., 1996)

NO

cGMP

Late night(phase advance)

Daily and circadian variations of cGMP

content in the hamster SCN

A

fmol

es c

GM

P /

g

prot

ein

0.05

0.10

0.15

0.20

0.25

0.30

0.35 (n=11)(n=10)

(n=17)

(n=9)

(n=10)

(n=13)

(n=11)(n=10)

(n=17)

(n=9)

(n=10)

(n=13)

** **

4 8 12 16 20 24 4 8 12 16 20 24

*

#

*

#

LD

B

CT

fmole

s cG

MP

/

g p

rote

in

0.05

0.10

0.15

0.20

0.25

0.30

0.35

(n=5)

(n=6) (n=6)

(n=5)(n=5)

(n=5)(n=5)

(n=4)

(n=5)

(n=4)

(n=6) (n=6)**

4 8 12 16 20 244 8 12 16 20 24

# #

** **

DD

Maximal values were found during the day

B

CT

fmol

es P

i /

g pr

otei

n x

5 m

in

200

400

600

800

1000

1200

1400

(n=4)

(n=5)

(n=5)

(n=5)

(n=5)

(n=4)(n=4) (n=4)

(n=5)

(n=5) (n=5)

(n=5)

4 8 12 16 20 24

#

* *

** **#

4 8 12 16 20 24

ZT

A

fmol

es P

i /

g pr

otei

n x

5 m

in

200

400

600

800

1000

1200

1400

(n=16)(n=21)

(n=20) (n=20)

(n=16)

(n=20)

(n=11)

(n=21)

(n=20)

(n=9)(n=9)

(n=11)

* *

# #

4 8 12 16 20 24 4 8 12 16 20 24

Daily and circadian variations of cGK

activity in the hamster SCN

LD

DD

Maximal values were found during the day

CTRL Pulse CTRL Pulse

pm

ole

s cG

MP

/

g p

rote

in

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.16

0.18

CT14 CT 18

*

A cGMP levels in the SCN

CTRL Pulse CTRL Pulse

fmol

esP

i/ g

pro

tein

x 5

min

0

50

100

150

200

250

300

CT14 CT 18

*

cGK activity in the SCNB

A: a 5-min light pulse increases cGMP levels at CT 18 but not at CT 14 (modified from Ferreyra and Golombek, 2001).

B: PKG activity significantly increased after a 5-min light pulse at CT 18 but was unaffected by the same photic stimulus at CT 14 (Golombek et al, 2004)

The GC-PKG pathway is involved light-induced phase advances

Phase advances of the circadian rhythm of locomotor activity are blocked by the NOS inhibitor L-NAME, the GC inhibitor ODQ and the cGK inhibitor KT-5823. On the other hand, the NO donor SNAP significantly increases light induced phase advances (Golombek et al, 2004).

0

20

40

60

80

100

120

140

160

Ph

ase

shif

t (m

inu

tes)

Vehicle

+ lightKT-5823

+ light

ODQ

+ lightL-NAME

+ light

Vehicle

+ light

SNAP

+ light

* **

*

dim light

CaMKII

Ca2+-Calmodulin

Ca2+

NOS

Glu

Ca2+

NMDA-R

Light

NO

PKG

GC

NOcGMP

Phase advance

?Phase delay

?

Late Night

Early Night