Cyclic adenosine monophosphate, calcium, acetylcholine and the current induced by adenosine in the Xenopus oocyte.

Abstract

SUMMARY1. The K+ current response to bath-applied adenosine has been studied on follicleenclosed full grown oocytes from Xenopu8 laevis, using the two electrodes voltageclamp technique.2. The response to adenosine was mimicked by forskolin, an activator of adenylate cyclase.3. Forskolin applied at low concentration potentiated the response to adenosine. 4. At low concentration, isoprenaline, a ,6-adrenergic agonist known to induce a potassium current via a rise ofadenosine 3',5'-phosphate (cyclic AMP) into the oocyte, potentiated the response to adenosine.5. Progesterone (10-5 M) reversibly induced a slight decrease (-24 %) of the response to adenosine.6. The calcium ionophore A23187 applied in normal external medium reduced the response to adenosine (about -70 %). Intracellular injection of EGTA induced an increase (+ 64 %) of the peak response to adenosine.7. Acetylcholine (05-10 ftM) inhibited the response to 3-10 ,CM adenosine by 44-91 %. This inhibition was suppressed by atropine and was seen even on cells which did not show any current in response to acetylcholine application. 8. The inhibition by ACh of the sensitivity to adenosine was long lasting (more than 1 h after the wash-out of ACh). A long term inhibition (-28 to -90 %) also occurred when ACh was applied alone and washed before adenosine application.9. It is concluded that in Xenopu8 oocyte: (i) increased cyclic AMP synthesis mediates the potassium response to adenosine; (ii) intracellular calcium ion concentration modulates this response; (iii) muscarinic stimulation induces a long-lasting inhibition of the sensitivity to adenosine.

Muscarinic receptor heterogeneity in follicle‐enclosed Xenopus oocytes

“…On the other hand, IK,cAMP had a mean reversal potential of −98 ± 2 mV (Fig. 1A), and the inhibitory effect of ACh on IK,cAMP had the same characteristics as those described before (Dascal et al 1985;Van Renterghem et al 1985;Stinnakre & Van Renterghem, 1986;Woodward & Miledi, 1987) (Fig. 1C).…”

Muscarinic receptor heterogeneity in follicle‐enclosed Xenopus oocytes

“…On the other hand, IK,cAMP had a mean reversal potential of −98 ± 2 mV (Fig. 1A), and the inhibitory effect of ACh on IK,cAMP had the same characteristics as those described before (Dascal et al 1985;Van Renterghem et al 1985;Stinnakre & Van Renterghem, 1986;Woodward & Miledi, 1987) (Fig. 1C).…”

Roles of protein kinases in neurotransmitter responses in Xenopus oocytes injected with rat brain mRNA

“…Maximum amplitudes of inward currents were measured and plotted relative to that before TFP treatment (means + SEM, n = 4). Renterghem, 1986). This indicates that cAMP of endogenous and exogenous origins functions in the same way.…”

Halide transport in Xenopus oocytes.

“…Patch clamp and voltage clamp data have shown that Xenopu8 oocytes contain Ca2+-activated Cl-channels (Miledi, 1982;Takahashi et al 1987). However, a dose of A23187 which is supra-maximal for opening of these channels in non-denuded oocytes (Stinnakre & Van Renterghem, 1986) failed to increase 36CI influx. This could be because the effects of A23187 are relatively transient compared to the uptake periods used here.…”

Muscarinic receptor heterogeneity in follicle‐enclosed Xenopus oocytes

“…On the other hand, IK,cAMP had a mean reversal potential of −98 ± 2 mV (Fig. 1A), and the inhibitory effect of ACh on IK,cAMP had the same characteristics as those described before (Dascal et al 1985;Van Renterghem et al 1985;Stinnakre & Van Renterghem, 1986;Woodward & Miledi, 1987) (Fig. 1C).…”

Roles of protein kinases in neurotransmitter responses in Xenopus oocytes injected with rat brain mRNA

“…Maximum amplitudes of inward currents were measured and plotted relative to that before TFP treatment (means + SEM, n = 4). Renterghem, 1986). This indicates that cAMP of endogenous and exogenous origins functions in the same way.…”

Halide transport in Xenopus oocytes.

“…Patch clamp and voltage clamp data have shown that Xenopu8 oocytes contain Ca2+-activated Cl-channels (Miledi, 1982;Takahashi et al 1987). However, a dose of A23187 which is supra-maximal for opening of these channels in non-denuded oocytes (Stinnakre & Van Renterghem, 1986) failed to increase 36CI influx. This could be because the effects of A23187 are relatively transient compared to the uptake periods used here.…”

Muscarinic receptor heterogeneity in follicle‐enclosed Xenopus oocytes

“…On the other hand, IK,cAMP had a mean reversal potential of −98 ± 2 mV (Fig. 1A), and the inhibitory effect of ACh on IK,cAMP had the same characteristics as those described before (Dascal et al 1985;Van Renterghem et al 1985;Stinnakre & Van Renterghem, 1986;Woodward & Miledi, 1987) (Fig. 1C).…”

Roles of protein kinases in neurotransmitter responses in Xenopus oocytes injected with rat brain mRNA

“…Maximum amplitudes of inward currents were measured and plotted relative to that before TFP treatment (means + SEM, n = 4). Renterghem, 1986). This indicates that cAMP of endogenous and exogenous origins functions in the same way.…”

Halide transport in Xenopus oocytes.

“…Patch clamp and voltage clamp data have shown that Xenopu8 oocytes contain Ca2+-activated Cl-channels (Miledi, 1982;Takahashi et al 1987). However, a dose of A23187 which is supra-maximal for opening of these channels in non-denuded oocytes (Stinnakre & Van Renterghem, 1986) failed to increase 36CI influx. This could be because the effects of A23187 are relatively transient compared to the uptake periods used here.…”