Laboratory of Chronobiology, Department of Science and Technology, National University of Quilmes, Buenos Aires, 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 INTRODUCCION 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. CELULARFISIOLOGICO POBLACIONAL CONDUCTUAL

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 RhythmPeriodExample 0,1 secelectroencephalogram 1 secelectrocardiogram 6 secbreathing rhythm 60 minpulsatile hormone secretion 90 minsleep staging sleep - wake cycle body temperature 28 daysmenstrual cycle 365 dayshibernation Ultradian Circadian Infradian 24 hours

En mamíferos, el reloj biológico se halla en los núcleos supraquiasmaticos (SCN) Output rhythms Behavior light Suprachiasmatic Nucleus (SCN)

CARACTERISTICAS NEUROQUIMICAS EXPRESION GENES RELOJ VIP PEPTIDO VASOACTIVO INTESTINAL AVP VASOPRESINA Región dorsomedial EXPRESION RITMICA Región ventrolateral EXPRESION INDUCIDA POR LUZ NSQ QO Los núcleos supraquiasmáticos (NSQ) son la sede del reloj biológico en mamíferos 3V: TERCER VENTRICULO QO: QUIASMA OPTICO INTRODUCCION Calb: Calbindina

Ciclo LUZ- OSCURIDAD INPUT OSCILADOR  TEMPERATURA  NIVELES HORMONALES  EXPRESION DE PROTEINAS  ACTIVIDAD LOCOMOTORA  ETC. OUTPUT Principales componentes del Sistema Circadiano ZEITGEBER (exógeno) oscilador (endógeno) Sincronización Acoplamiento

Mecanismo de oscilación: el reloj molecular CITOPLASMA NUCLEO CKI  CRY PER Degradación vía proteosoma Per Cry Rev otros Genes blancoE-box CLOCKBMAL CRY PER CRY PER INTRODUCCION

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

(PRC) Phase response curve (PRC)

 Ca 2+ CaMKII Ca 2+ -Calmodulin Glu Ca 2+ 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

 Ca 2+ CaMKII Ca 2+ -Calmodulin NOS Glu Ca 2+ 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)

 Ca 2+ CaMKII Ca 2+ -Calmodulin NOS Glu Ca 2+ NMDA-R Light There is a direct pathway between CaMKII and NOS in the SCN (Agostino et al, 2004, Neurochem Int 44: )

CaMKII Ca 2+ -Calmodulin  Ca 2+ NOS PKG GC Glu Ca 2+ 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 LD DD Maximal values were found during the day

Daily and circadian variations of cGK activity in the hamster SCN LD DD Maximal values were found during the day

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 On the other hand, the NO donor SNAP significantly increases light induced phase advances (Golombek et al, 2004).

CaMKII Ca 2+ -Calmodulin  Ca 2+ NOS Glu Ca 2+ NMDA-R Light NO PKG GC NO cGMP Phase advance ? Phase delay ? Late Night Early Night