Abstract
The modulatory effects of exogenous applications of adenosine on luminous organs (photophores) of the fish Porichthys were studied. Pretreatment of photophores with adenosine (10^β7^ to 10^β3^ M) potentiated both phases of adrenaline induced luminescence. The first peak of light (Lmax1) showed a 3βfold increase following 10^β7^ M adenosine treatment; a maximal increase of 12βfold was observed with 10^β3^ M adenosine. The second peak of light (Lmax2) exhibited a similar doseβresponse curve, but the maximal increase was attained with 10^β4^ M adenosine. The potentiating effect of 1 uM adenosine on light emission triggered by adrenaline increased for adrenaline concentrations ranging from 10^β7^ to 10^β4^ M for Lmax1, but it remained stable for Lmax2. All 4 P1βpurinergic agonists tested at the final concentration of 10^β4^ M induced a potentiation of adrenaline luminescence with the following rank of potency: LβPIA > NECA > CADO β₯ CHA = ADO for Lmax1 and NECA > CADO > ADO > CHA > LβPIA for Lmax2. The potentiating effect of adenosine was antagonized with the following rank of potency by the Pβ1 purinergic antagonists: CPT > DPMX β₯ AMINO > THEO for Lmax1 and CPT > AMINO > THEO β₯ DPMX for Lmax2. According to the classification of purinergic receptors, our results suggest that P1βpurinergic receptors might be implicated in the adenosine potentiation of Porichthys adrenaline luminescence. Experiments also showed that norβadrenaline luminescence is inhibited by 1 uM adenosine pretreatment. Further work will be necessary to elucidate the mechanism involved in the modulatory roles played by the purinergic receptors on adrenaline and noradrenaline luminescence in Porichthys photophores. Β© 1993 WileyβLiss, Inc.