Biochemical and pharmacological evidence for the presence of A1 but not A2a adenosine receptors in the brain of the low vertebrate teleost Carassius auratus (goldfish)

Neurochem Int. 1995 Apr;26(4):411-23. doi: 10.1016/0197-0186(94)00112-8.

Abstract

In whole brain membranes of goldfish, 3H-chlorocyclopentyladenosine bound to adenosine A1 receptors. The A1 receptors were ubiquitously distributed in the brain with a maximum in the hypothalamus and a minimum in the spinal cord. In superfused goldfish cerebellar slices, cyclohexyladenosine inhibited the cyclic AMP accumulation stimulated by forskolin and the selective adenosine A1 receptor antagonist, 8-cyclopentyltheophylline, reversed this effect. In the same brain preparation, 30 mM K+ stimulated the release of glutamate, glutamine, glycine and GABA in a Ca(2+)-dependent manner, whereas the aspartate and taurine release was Ca(2+)-independent. Cyclohexyladenosine, in a dose-dependent manner, inhibited the 30 mM K(+)-evoked release of glutamate whereas that of aspartate was unaffected. The CHA inhibition of glutamate-evoked release was reversed by 8-cyclopentyltheophylline. The adenosine A2a receptors were not detectable in whole brain membranes of goldfish either using the specific agonist 3H-CGS 21680 or 3H-5'-N-ethylcarboxamidoadenosine. The presence of A2b seems to be suggested by the NECA stimulation of cyclic AMP accumulation, which was reversed by 8-cyclopentyltheophylline. The results, taken together, indicate that adenosine has a neuromodulatory function in the nervous system of lower vertebrates which is comparable to that described in mammalian brain.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine / analogs & derivatives
  • Adenosine / metabolism
  • Adenosine-5'-(N-ethylcarboxamide)
  • Animals
  • Goldfish / metabolism*
  • Hydrogen-Ion Concentration
  • Mammals / metabolism*
  • Neurotransmitter Agents / physiology*
  • Phenethylamines / metabolism
  • Radioligand Assay
  • Receptors, Purinergic P1 / analysis*
  • Receptors, Purinergic P1 / physiology
  • Species Specificity
  • Temperature

Substances

  • Neurotransmitter Agents
  • Phenethylamines
  • Receptors, Purinergic P1
  • 2-(4-(2-carboxyethyl)phenethylamino)-5'-N-ethylcarboxamidoadenosine
  • Adenosine-5'-(N-ethylcarboxamide)
  • N(6)-cyclohexyladenosine
  • 2-chloro-N(6)cyclopentyladenosine
  • Adenosine