Adenosine A1 receptors in rat brain synaptosomes: Transductional mechanisms, effects on glutamate release, and preservation after metabolic inhibition

Maria P. Abbracchio, Roberta Brambilla, Manuela Camisa, G. Enrico Rovati, Rosaria Ferrari, Laura Canevari, Fiorenzo Dagani, Flaminio Cattabeni

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Synaptosomes from various rat brain areas show saturable and specific binding to an adenosine A1 receptor ligand [Dagani et al. (1993): Drug Dev Res 28:359–363]. In this study, the functional correlates of these receptors were characterized in rat hippocampal synaptosomes by evaluating the ability of the adenosine analogue cyclo‐pentyl‐adenosine (CPA) to modulate KCI‐ and veratridine‐induced glutamate outflow. CPA concentration‐dependently reduced both depolarization‐induced glutamate release and the associated increases of intrasynaptosomal Ca2+ concentrations. Maximal reduction by 100 μM CPA (30% and 40% with respect to control for veratridine‐ and KCI‐induced release, respectively) was completely antagonized by the xanthine adenosine receptor blocker bamyfilline, confirming the involvement of adenosine A1 receptors. CPA selectively affected outflow of glutamate, with no significant influence on release of aspartate or GABA. Experiments performed in the absence of extrasynaptosomal Ca2+ ions suggested that adenosine selectively modulates glutamate Ca2+ ‐dependent vesicular pool. Transductional studies showed that mobilization of Ca2+ from intrasynaptosomal inositol‐phosphate‐sensitive stores does not contribute to adenosine effects on release, therefore implying that CPA reduction of Ca2+ influx is due to direct effects on membrane Ca2+ conductance. Conversely, activation of A1 receptors resulted in inhibition of forskolin‐stimulated cAMP production in the same agonist concentration range effective on modulation of release, suggesting that this second messenger may play a role in the presynaptic effects of adenosine analogues. Finally, CPA reduced both glutamate efflux and the increases of internal Ca2+ concentrations associated with block of synaptosomal energy metabolism with rotenone and iodoacetic acid, suggesting that presynaptic A1 receptors represent a strategic site of action for adenosine also under experimental conditions resembling brain ischemia and hypoxia. © 1995 Wiley‐Liss, Inc.

Original languageEnglish (US)
Pages (from-to)119-129
Number of pages11
JournalDrug Development Research
Volume35
Issue number3
DOIs
StatePublished - 1995
Externally publishedYes

Fingerprint

Adenosine A1 Receptors
Synaptosomes
Adenosine
Rats
Glutamic Acid
Brain
Iodoacetic Acid
Veratridine
Presynaptic Receptors
Brain Hypoxia-Ischemia
Rotenone
Purinergic P1 Receptors
Xanthine
Second Messenger Systems
Aspartic Acid
gamma-Aminobutyric Acid
Energy Metabolism
Chemical activation
Modulation
Ions

Keywords

  • brain ischemia
  • glutamatergic transmission
  • presynaptic adenosine receptors

ASJC Scopus subject areas

  • Drug Discovery
  • Organic Chemistry
  • Pharmacology

Cite this

Adenosine A1 receptors in rat brain synaptosomes : Transductional mechanisms, effects on glutamate release, and preservation after metabolic inhibition. / Abbracchio, Maria P.; Brambilla, Roberta; Camisa, Manuela; Rovati, G. Enrico; Ferrari, Rosaria; Canevari, Laura; Dagani, Fiorenzo; Cattabeni, Flaminio.

In: Drug Development Research, Vol. 35, No. 3, 1995, p. 119-129.

Research output: Contribution to journalArticle

Abbracchio, Maria P. ; Brambilla, Roberta ; Camisa, Manuela ; Rovati, G. Enrico ; Ferrari, Rosaria ; Canevari, Laura ; Dagani, Fiorenzo ; Cattabeni, Flaminio. / Adenosine A1 receptors in rat brain synaptosomes : Transductional mechanisms, effects on glutamate release, and preservation after metabolic inhibition. In: Drug Development Research. 1995 ; Vol. 35, No. 3. pp. 119-129.
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