Identification of PAC1 receptor isoform mRNAs by real-time PCR in rat suprachiasmatic nucleus

Oct 26, 2002Brain research. Molecular brain research

Detecting PAC1 receptor messenger RNA types in the rat brain's internal clock area

AI simplified

Circadian Biology on OpenScience ↗PubMed ↗DOI ↗

Abstract

PAC1 receptor mRNA expression levels in rat suprachiasmatic nucleus (SCN) do not vary significantly with time of day.

PACAP is involved in the photic resetting of the circadian clock in rodents.
PAC1 and VPAC2 receptor mRNA are present in the rat SCN, while VPAC1 is not.
Two PAC1 receptor variants, PAC1(null) and PAC1(hop1/2), were identified in the SCN.
No other PAC1 receptor variants were detected at any time of day.
The combined expression of PAC1(null) and PAC1(hop) variants remains stable throughout a 12:12-h light:dark cycle.
Changes in PAC1 receptor expression do not account for phase-dependent effects of PACAP on circadian behavior.

AI simplified

The pituitary adenylate cyclase-activating polypeptide (PACAP) has been implicated in the photic resetting of the rodent circadian clock in the suprachiasmatic nucleus (SCN). PACAP can exert its effects via VPAC1, VPAC2 and PAC1 G-protein coupled receptors. PAC1 and VPAC2, but not VPAC1, mRNA is expressed in rat SCN. A variety of PAC1 receptor splice variants have been described showing differences in ligand binding affinity and selectivity, G-protein coupling and ability to activate signal transduction pathways. The present experiments used PCR with isoform specific primers to determine which PAC1 variants are expressed in rat SCN. The PAC1(null) isoform and a variant containing a single 28-amino acid insert in the third intracellular (IC3) loop (hop1/2) were detected. No other IC3 variants (hip, hip-hop), N-terminal variants (PAC1(short), PAC1(very short) and PAC1(3a)) or the variant differing in transmembrane II and IV (PAC1TM4) were detected in SCN obtained at any time of day. A quantitative real-time PCR assay was established which measured combined expression of the PAC1(null/hop) variants in rat SCN during a 12:12-h light:dark (L:D) cycle. There was no significant variation of PAC1 mRNA expression (PAC1(null)+PAC1(hop)) with time of day. Nor was there a significant difference in the proportion of these two variants with time of day. These results indicate that the phase-dependency of the actions of PACAP on SCN firing and circadian behaviour are not mediated by changes in the level of expression of PAC1 receptor mRNA, nor by phase-dependent expression of PAC1 receptor variants with altered ligand binding, G-protein coupling or signalling characteristics.

Full Text

Full text is available at the source.

View full text (XML) ↗View full text ↗

Identification of PAC1 receptor isoform mRNAs by real-time PCR in rat suprachiasmatic nucleus

Abstract

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief