Rhythmic variation in β1‐adrenergic receptor mRNA levels in the rat pineal gland: circadian and developmental regulation

Oct 3, 1998The European journal of neuroscience

Daily and developmental changes in beta1-adrenergic receptor gene levels in the rat's pineal gland

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Abstract

A marked day/night difference in beta1-adrenergic receptor mRNA levels is evident only after postnatal day 10.

Noradrenaline is released in large quantities in the rat pineal gland at the onset of darkness, driving melatonin synthesis.
Noradrenaline activates the cyclic AMP signalling pathway through interactions with beta1-adrenergic receptors.
Cyclic AMP-inducible genes, including those regulated by CREB and ICER, are crucial for hormone production in the pineal gland.
Beta1-adrenergic receptor mRNA exhibits a circadian rhythm with elevated levels during the dark period, which persists in constant darkness but is abolished without sympathetic innervation.
The expression of the beta1-adrenergic receptor gene may be controlled by the cyclic AMP-signalling pathway, suggesting a feedback mechanism.

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In the rat pineal gland noradrenaline is released in large quantities from sympathetic nerve endings at the onset of darkness, thereby driving rhythmic melatonin synthesis with elevated levels at night-time. Upon release, noradrenaline interacts with postsynaptic beta1-adrenergic receptors to activate the cyclic AMP signalling pathway. Well characterized third messengers of this signalling cascade affect cyclic AMP-inducible genes that are crucially involved in initiation, maintenance and termination of hormone production. Among these third messengers are CREB (cyclic AMP responsive element binding protein) as an activating and ICER (inducible cyclic AMP early repressor) as an inhibitory transcription factor. Because a cyclic AMP-inducible promoter element is present on the beta1-adrenergic receptor gene, the expression of the receptor itself may be under control of the cyclic AMP-signalling pathway. By in situ hybridization, Northern blot analysis and RT-PCR we demonstrate a day/night rhythm in beta1-adrenergic receptor mRNA in the rat pineal gland with elevated levels during the dark period. As this rhythm persists, under constant darkness but is abolished upon removal of the sympathetic innervation, it is truly circadian. A marked day/night difference in the levels of beta1-adrenergic receptor mRNA becomes evident only after postnatal day 10, coinciding with the appearance of a functional cyclic AMP signalling pathway in the rat pineal gland. Furthermore, targeting ICER expression by transfection of pinealocytes with an antisense ICER construct, clearly indicates that the levels of the beta1-adrenergic receptor mRNA are regulated by the cyclic AMP-signalling pathway in a feedback mechanism.

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Rhythmic variation in β1‐adrenergic receptor mRNA levels in the rat pineal gland: circadian and developmental regulation

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