title: Light-induced phase shift in the Syrian hamster (Mesocricetus auratus) is attenuated by the PACAP receptor antagonist PACAP6-38 or PACAP immunoneutralization.
abstract: Circadian rhythms generated by the suprachiasmatic nucleus (SCN) are daily adjusted (entrained) by light via the retinohypothalamic tract (RHT). The RHT contains two neurotransmitters, glutamate and pituitary adenylate cyclase-activating polypeptide (PACAP), which are believed to mediate the phase-shifting effects of light on the clock. In the present study we have elucidated the role of PACAP in light-induced phase shifting at early night in hamsters and shown that (i) light-induced phase delay of running-wheel activity was significantly attenuated by a specific PAC1 receptor antagonist (PACAP6-38) or by immunoblockade with a specific anti-PACAP antibody injected intracerebroventricularly before light stimulation; (ii) PACAP administered close to the SCN was able to phase-delay the circadian rhythm of running-wheel activity in a similar way to light; (iii) PACAP was present in the hamster RHT, colocalized with melanopsin, a recently identified opsin which has been suggested to be a circadian photopigment. The findings indicate that PACAP is a neurotransmitter of the RHT mediating photic information to the clock, possibly via melanopsin located exclusively on the PACAP-expressing cells of the RHT.
authors: Department of Clinical Biochemistry, Bispebjerg Hospital, University of Copenhagen, Bispebjerg Bakke 23, DK-2400 Copenhagen NV, Denmark.
authors: A L
authors: AL
authors: Bergström
authors: J
authors: J
authors: Hannibal
authors: P
authors: P
authors: Hindersson
authors: J
authors: J
authors: Fahrenkrug
mesh_terms: D000818:Animals; D000906:Antibodies; D001522:Behavior, Animal; D002940:Circadian Rhythm / Q000187:drug effects* / Q000502:physiology; D006224:Cricetinae; D007031:Hypothalamus / Q000502:physiology*; D007150:Immunohistochemistry; D008027:Light; D008297:Male; D008647:Mesocricetus; D009434:Neural Pathways / Q000737:chemistry / Q000502:physiology; D009474:Neurons / Q000187:drug effects; D009479:Neuropeptides / Q000008:administration & dosage / Q000032:analysis / Q000276:immunology / Q000494:pharmacology* / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000032:analysis; D010446:Peptide Fragments / Q000494:pharmacology*; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone / Q000037:antagonists & inhibitors; D012160:Retina / Q000737:chemistry / Q000502:physiology*; D017299:Rod Opsins / Q000187:drug effects / Q000502:physiology; D012420:Running; D013493:Suprachiasmatic Nucleus / Q000187:drug effects*; D009435:Synaptic Transmission / Q000187:drug effects; D000099210:Melanopsin
chemical_list: D000906:Antibodies; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D010446:Peptide Fragments; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D051236:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide; D051237:Receptors, Pituitary Adenylate Cyclase-Activating Polypeptide, Type I; D011979:Receptors, Pituitary Hormone; D017299:Rod Opsins; D000099210:Melanopsin; C075647:pituitary adenylate-cyclase-activating-peptide (6-38)