Presynaptic adenosine A1 receptors regulate retinohypothalamic neurotransmission in the hamster suprachiasmatic nucleus

Richard J. Hallworth, Matthew Cato, Costa Colbert, Michael A. Rea

Research output: Contribution to journalArticle

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Abstract

Adenosine has been implicated as a modulator of retinohypothalamic neurotransmission in the suprachiasmatic nucleus (SCN), the seat of the light-entrainable circadian clock in mammals. Intracellular recordings were made from SCN neurons in slices of hamster hypothalamus using the in situ whole-cell patch clamp method. A monosynaptic, glutamatergic, excitatory postsynaptic current (EPSC) was evoked by stimulation of the optic nerve. The EPSC was blocked by bath application of the adenosine A1 receptor agonist cyclohexyladenosine (CHA) in a dose-dependent manner with a half-maximal concentration of 1.7 μM. The block of EPSC amplitude by CHA was antagonized by concurrent application of the adenosine A1 receptor antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX). The adenosine A2A receptor agonist CGS21680 was ineffective in attenuating the EPSC at concentrations up to 50 μM. Trains of four consecutive stimuli at 25 ms intervals usually depressed the EPSC amplitude. However, after application of CHA, consecutive responses displayed facilitation of EPSC amplitude. The induction of facilitation by CHA suggested a presynaptic mechanism of action. After application of CHA, the frequency of spontaneous EPSCs declined substantially, while their amplitude distribution was unchanged or slightly reduced, again suggesting a mainly presynaptic site of action for CHA. Application of glutamate by brief pressure ejection evoked a long-lasting inward current that was unaffected by CHA at concentrations sufficient to reduce the evoked EPSC amplitude substantially (1 to 5 μM), suggesting that postsynaptic glutamate receptor-gated currents were unaffected by the drug. Taken together, these observations indicate that CHA inhibits optic nerve-evoked EPSCs in SCN neurons by a predominantly presynaptic mechanism.

Original languageEnglish
Pages (from-to)230-240
Number of pages11
JournalJournal of Neurobiology
Volume52
Issue number3
DOIs
StatePublished - Sep 2002
Externally publishedYes

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Adenosine A1 Receptors
Suprachiasmatic Nucleus
Excitatory Postsynaptic Potentials
Synaptic Transmission
Cricetinae
Optic Nerve
Adenosine A2 Receptor Agonists
Adenosine A1 Receptor Agonists
Adenosine A1 Receptor Antagonists
Neurons
Circadian Clocks
Glutamate Receptors
Baths
Adenosine
Hypothalamus
Glutamic Acid
Mammals
Light
Pressure
Pharmaceutical Preparations

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)

Cite this

Presynaptic adenosine A1 receptors regulate retinohypothalamic neurotransmission in the hamster suprachiasmatic nucleus. / Hallworth, Richard J.; Cato, Matthew; Colbert, Costa; Rea, Michael A.

In: Journal of Neurobiology, Vol. 52, No. 3, 09.2002, p. 230-240.

Research output: Contribution to journalArticle

Hallworth, Richard J. ; Cato, Matthew ; Colbert, Costa ; Rea, Michael A. / Presynaptic adenosine A1 receptors regulate retinohypothalamic neurotransmission in the hamster suprachiasmatic nucleus. In: Journal of Neurobiology. 2002 ; Vol. 52, No. 3. pp. 230-240.
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