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Evidence of depolarization-induced cAMP increase in the superior cervical ganglion of several mammalian species
Gen. Pharmac., 1976, Vol. 7, pp. 267 to 270. Peroamon Press. Printed in Great Britain
EVIDENCE OF DEPOLARIZATION-INDUCED cAMP INCREASE IN THE SUPERIOR CERVICAL GANGLION OF SEVERAL MAMMALIAN SPECIES PETER KALIX and PHILIPPE ROCH Department of Pharmacology, University of Geneva, Geneva, Switzerland (Received 6 October 1975)
Abstract---1. The activation of cAMP synthesis resulting from exposure of superior cervical ganglion (SCG) tissue to high K + solutions observed in calf has been found to occur in three other mammalian species, namely rat, cat, and rabbit. 2. The cAMP accumulation in the ganglion of calf is much less pronounced than that occurring in the other species. The enhancing effect of theophylline on the increase of cAMP was found to be much greater in the SCG of calf than in that of other species. When veratridine was used as the depolarizing agent the species differences were found to be similar to those observed after potassium stimulation. 3. The effectiveness of several other depolarizing agents in causing an increase in the cAMP level was tested in rabbit SCG.
INTRODUCTION
ISOLATED superior cervical ganglia (SCG) of rabbit have been shown to react to electrical stimulation of the preganglionic nerve with an increase in c A M P synthesis (McAfee et al., 1971), and it has been found that electrical impulses applied in situ can accelerate the conversion of tritiated adenine to 3H-cAMP in SCG of cat (Chatzkel et al., 1974). It has further been demonstrated that cholinomimetic agents can cause an increase in c A M P concentration in rabbit SCG that is pharmacologically analogous to that caused by electrical stimulation (Kalix et al., 1974). Based on the experiments carried out on rabbit ganglia, as well as on other studies (Libet, 1970; K e b a b i a n & Greengard, 1971), it has been suggested that the c A M P level might be a modulating factor for transmission through peripheral ganglia (Greengard & Kebabian, 1974). Recent experiments with bovine SCG have shown that increases in c A M P can also be induced by incubation in media containing either veratridine (Kalix & Roch, 1975) or elevated K+-concentrations (Roch & Kalix, 1975). In an attempt to relate the above findings and to determine the extent to which they could be considered generally applicable, the c A M P synthetizing system of the SCG of several species was studied with regard to its sensitivity to potassiumand veratridine-depolarization and the results were compared. In addition, several other depolarizing agents were tested for their possible effect on the c A M P level in rabbit SCG. METHODS
Superior cervical ganglia (SCG) were removed from unanaesthetized animals immediately after their death and 267
kept in an ice-cold physiological solution for a time varying from 5 to 20 min. This medium had the following composition (mml/1): NaC1 136; KCI 5.6; NaHCO3 20.0; NaH/PO4 1.2; CaC12 2.2; MgC12 1.2; glucose 5.5 and was bubbled with a mixture of 5% CO2-95~,, 02. After removal of the connective tissue, individual samples of whole ganglia of rat, ganglia of rabbit halved lengthwise, quartered ganglia of cat or small blocks of calf ganglion tissue (Roch & Kalix, 1975) were incubated for approx 30 min at 37°C in the solution which was kept saturated with the gas mixture; these conditions having been shown in rabbit (Kalix et al., 1974) to permit the ganglia to remain fully responsive to electrical stimulation. The samples were then transferred to vials containing the incubation medium to which either depolarizing substances, theophylline or both had been added; alternatively, part of the Na + was replaced by K ÷ and this solution was used both with and without the addition of theophylline. At the end of the incubation period, the tissue was denaturated, an extract was assayed for cAMP according to the method of Brown et al. (1971) and the amount of protein of the sample was determined by the method of Lowry et al. (1951). Details of these procedures have been previously described (Roch & Kalix, 1975). Veratridine and cevadine were obtained from Aldrich Chemicals, Milwaukee/USA; aconitine and delphinine from Fluka AG, Buchs/Switzerland; ouabain and theophylline from E. Merck AG, Darmstadt/Germany. RESULTS The c A M P concentration in untreated SCG tissue that h a d been equilibrated for approx 30rain in Locke solution, was found to range from 14.8 (calf) to 19.9 (rabbit) pmoles/mg of protein (Table 1). W h e n theophylline was added to the medium in order to prevent the breakdown of cAMP, a moderate increase in the basal c A M P concentration was observed, ranging from 54% (rabbit) to 77% (rat). Similar results
2(~S
P l m R KALIX ANt:' PHILIPI'I:! ROCH
l'ablc 1. Increases in cAMPconlcnt induced by depolarizing media and by theophylline m the superior cervical ganglion of different species
I
Rat
Locke
Theophylline
K+
(10-2M)
(10-1M)
plus
theophylline
Veratridine
plus
(10-2H)
(10-2M)
Cat
Calf
15.8
+ 2.5
(3;30)
19.9
+ 1.9
(9;30)
15.2
+ 5,2
(3;30)
14.8
+ 1.3
(17;30
27.9
+ 1.4
(3; 6)
30.6
+ 6.3
(3~
6)
24.0
+ l.l
(3;
23.7
+ i.0
{62;
58.9
+ 7.5
(3~
6)
68.7
+ 8.7
(3;
6)
18.5
+ 2.6
( 5; ~
112.4
+ 4.5
(3;
6)
168,6
+40.1
(3; 6)
68.5
+ 3.1
(37;
9
74.8
+ 8.7
(4;
24.8
+ 2.4
( 4;
9
252.5
~58.0
(3; 4)
76.5
~ 9.0
( 4;
Z
(5XI0-4M)
theophylline
Rabbit
165.6
+17.8
(3+
6)
43.7
+ 4,7
(3;
6)
6)
4)
38+0
+ 1.7
(3; 6)
9
Fhc basal cAMP concentration in the ganglia first line) was determined a~er a 30 min equilibration period in Locke solution. In parenthesis: number of experiments; minutes of incubation. Values* are taken from Roch & Kalix (1975), all values are expressed as pmoles cAMP per mg protein. (not shown) were obtained with other phosphodiesterase-inhibitors. Replacement of 100raM Na + of the incubation medium with K + resulted in a three- to four-fold increase of the c A M P level ill rat and rabbit ganglia, bnt in only a comparatively small increase in calf ganglia. On the other hand, when theophylline was present in b o t h the control and the test medium, the response of rat and rabbit ganglia to high K + was amplified by a factor of approx two, and that of calf ganglion tissue by a factor of a b o u t four. Cat ganglia, however, responded to potassium stimulation with
only a moderate increase in c A M P content even after addition of theophylline. In an analogous series of experiments, veratridine, a depolarizing alkaloid, was used to induce the rise of the ganglionic c A M P level. In general, its effects were found to be similar to those of high potassium. It is noteworthy that when the incubation medium contained veratridine, the species differences observed paralleled those described above for K +. In a previous study on calf ganglia (Kalix & Roch, 1975), the increase in ganglionic c A M P due to veratridine was found to be rapid and, in spite of the pres-
pmoles cAMP/ mg p r o t e i n 300 -
100
.~°
0
~
0
I
t 4
1 9
i 20 m i n i n c u b a t i o n
Fig. 1. Time course of the c A M P accumulation in rabbit SCG during exposure to solutions containing
10mM theophylline plus one of the following agents: 0.500mM veratridine II, 0.300mM cevadine D, 0.050 mM ouabain &, 0.500 mM aconitine II.
cAMP in superior cervical ganglion ence of theophylline, transient. In contrast, maximally effective doses of ouabain were shown to produce a much slower but sustained cAMP increase. In the present study, the same phenomenon was observed in similar experiments on rabbit ganglia (Fig. 1). In these ganglia, high concentrations of two other depolarizing alkaloids, i.e. aconitine and cevadine (a structural analogue of veratridine) were also found to cause an increase in cAMP content. Exposure of rabbit ganglia to solutions containing delphinine, an alkaloid pharmacologically similar to aconitine, for periods ranging from 1 to 20rain, caused no significant change in cAMP content.
269
observed might not also reflect species variations in the phosphodiesterase activity similar to those demonstrated above for bovine SCG. It should be mentioned, however, that the mechanism leading to increased cAMP synthesis in the cortex appears to differ from the one involved in the ganglion (Roch & Kalix, 19751. In rabbit ganglia, the cAMP accumulation induced by exposure to high potassium is comparable in magnitude to that induced by cholinomimetic stimulation; in this species, the cAMP level rises about two-fold upon exposure to carbachol alone, but fourfold when theophylline or other phosphodiesterase inhibitors are present during stimulation (Kalix et al., 1974). The two types of stimulation do not seem to DISCUSSION be interdependent, however, since neither a nicotinic The results described above lend support to the nor a muscarinic antagonist reduced the K +-induced assumption that depolarization-dependent cAMP ' cAMP increase in bovine SCG (Roch & Kalix, 1975). In all four species examined parallel experiments synthesis is of common occurrence in mammalian SCG. The basal cAMP concentration was found to were performed in which veratridine was used instead be approximately the same in the SCG of each of of high potassium, and the results were practically the four species examined and the values obtained the same. An identical time course pattern for the were similar to those reported in the literature for stimulating effect of veratridine and ouabain respectthe SCG of calf (Kebabian & Greengard, 1971), rat ively, previously reported for calf ganglia (Kalix & (Lindl & Cramer, 1974) and rabbit (McAfee et al., Roch, 1975), was observed in rabbit ganglion tissue 197l). In all four species, exposure of the ganglia to as well. Furthermore, in rabbit, as in calf, the cAMP theophylline resulted in a moderate rise in the level content which had been increased by exposure to veratridine, decreased after longer exposure in spite of of cAMP. In a previous paper, we have reported that the the high concentration of theophylline in the medium, cAMP level in calf SCG can be raised by exposing a peculiarity which cannot' be explained at present. the tissue to media containing high concentrations Aconitine and cevadine, two alkaloids with pharmaof K ÷ (Roch & Kalix, 1975). In the present exper- cological properties similar to those of veratridine, iments, depolarizing media were found to cause an were also seen to cause a cAMP increase in ganglion increase in cAMP concentration in three further spe- tissue. The capacity to induce depolarization would cies; rat, rabbit and cat. The cAMP increase in calf therefore seem to be the common characteristic of ganglion was found to be considerably smaller than these substances, responsible for the observed activation of cAMP synthesis. The present study demonthat observed in rat, rabbit or cat. The extent to which this response could be amplified by theophyl- strates that the mechanism of increased cAMP synline, on the other hand, was found to be greater in thesis is a consequence, probably indirect, of depolaricalf than in the other species. The observation that zation, is operative in the SCG of at least several high K ÷ and theophylline individually cause only mammalian species. relatively small increases, whereas their simultaneous Acknowledgement--The authors are grateful to Mrs. J. presence in the medium results in a comparatively Noebels for help with the English of the manuscript, large cAMP accumulation, might indicate that in calf, phosphodiesterase is activated by its substrate. This REFERENCES strong dependence of the cAMP accumulation on the presence of a phosphodiesterase-inhibitor appears to BROWN B., ALBANOJ., EK1NS R., SGHERZI A. & TAMPION be characteristic of bovine ganglion tissue since W. (1971) Saturation assay for cyclic AMP using endogenous binding protein. Biochem. J. 121, 561-562. marked increases in cAMP concentration without phosphodiesterase inhibition have been shown to CrIATZKELS., Z1MMERMANI. & BERG A. (1974) Modulation of cyclic AMP synthesis in the cat superior cervical occur in rat and rabbit. Comparable observations ganglion by short term presynaptic stimulation. Brain have been made in cerebral cortex slices, in this tissue Res. 80, 523 529. it was demonstrated that an accelerated conversion GREENGARD P. & KEBABIAN J. W. (1974).Role of cyclic of prelabelled ATP to cAMP can be caused by depoAMP in synaptic transmission in the mammalian perilarizing media (Shimizu & Daly, 1972). Both in this pheral nervous system. Fedn Proc. Fedn Am. Socs exp. and another study (Rail & Sattin, 1970) considerable Biol. 33, 1059-1067. species differences in the amplitude of the response KALIX P., McAFEE D., SCHORDERETM. & GREENGARDP. (1974) Pharmacological analysis of synaptically mediated were found. As these studies were conducted without increase in cyclic AMP in rabbit superior cervical gangconcomitant phosphodiesterase-inhibition, it would lion. J, Pharmac. exp. Ther. 188. 676-687. be of interest to determine whether the differences
270
P~iTER KALIX AND PHILIPPE ROCH
KAL1X P. & ROC'H PH. (1975) Effect of dcpolarizing agents on the adenosine-3',5'-monophosphate content of the bovine superior cervical ganglion. NawTv~7 Schmiedebo'~f Arch. Pharmac. 291, 131 137. KEnABIAN J. W. & GREENGARD P. (1971) Dopamine sensitive adenylate cyclase: possible role in synaptic transmission. Science, N.Y. 174, 1346 1349. LmET B. (1970)Generation of slow inhibitory and excitatory postsynaptic potentials. Fedn Proc. Fed, Am. Sots exp. Biol. 29, 1945 1956. L1NDL T, & CRAMER H. (1974) Formation. accumulation and release of cyclic A M P induced by histamine in the superior cervical ganglion of the rat i~ z:itro. Biochim. biophys. Acta 343, 182 191. LOWRY O., ROSEBROUGH N., FARR A & RANDALL R. (1951) Protein measurement with the Folin phenol reagent. J. biol. Chem. 193, 265-275.
Mc:AFLI D.. S('HORDERt
EVIDENCE OF DEPOLARIZATION-INDUCED cAMP INCREASE IN THE SUPERIOR CERVICAL GANGLION OF SEVERAL MAMMALIAN SPECIES PETER KALIX and PHILIPPE ROCH Department of Pharmacology, University of Geneva, Geneva, Switzerland (Received 6 October 1975)
Abstract---1. The activation of cAMP synthesis resulting from exposure of superior cervical ganglion (SCG) tissue to high K + solutions observed in calf has been found to occur in three other mammalian species, namely rat, cat, and rabbit. 2. The cAMP accumulation in the ganglion of calf is much less pronounced than that occurring in the other species. The enhancing effect of theophylline on the increase of cAMP was found to be much greater in the SCG of calf than in that of other species. When veratridine was used as the depolarizing agent the species differences were found to be similar to those observed after potassium stimulation. 3. The effectiveness of several other depolarizing agents in causing an increase in the cAMP level was tested in rabbit SCG.
INTRODUCTION
ISOLATED superior cervical ganglia (SCG) of rabbit have been shown to react to electrical stimulation of the preganglionic nerve with an increase in c A M P synthesis (McAfee et al., 1971), and it has been found that electrical impulses applied in situ can accelerate the conversion of tritiated adenine to 3H-cAMP in SCG of cat (Chatzkel et al., 1974). It has further been demonstrated that cholinomimetic agents can cause an increase in c A M P concentration in rabbit SCG that is pharmacologically analogous to that caused by electrical stimulation (Kalix et al., 1974). Based on the experiments carried out on rabbit ganglia, as well as on other studies (Libet, 1970; K e b a b i a n & Greengard, 1971), it has been suggested that the c A M P level might be a modulating factor for transmission through peripheral ganglia (Greengard & Kebabian, 1974). Recent experiments with bovine SCG have shown that increases in c A M P can also be induced by incubation in media containing either veratridine (Kalix & Roch, 1975) or elevated K+-concentrations (Roch & Kalix, 1975). In an attempt to relate the above findings and to determine the extent to which they could be considered generally applicable, the c A M P synthetizing system of the SCG of several species was studied with regard to its sensitivity to potassiumand veratridine-depolarization and the results were compared. In addition, several other depolarizing agents were tested for their possible effect on the c A M P level in rabbit SCG. METHODS
Superior cervical ganglia (SCG) were removed from unanaesthetized animals immediately after their death and 267
kept in an ice-cold physiological solution for a time varying from 5 to 20 min. This medium had the following composition (mml/1): NaC1 136; KCI 5.6; NaHCO3 20.0; NaH/PO4 1.2; CaC12 2.2; MgC12 1.2; glucose 5.5 and was bubbled with a mixture of 5% CO2-95~,, 02. After removal of the connective tissue, individual samples of whole ganglia of rat, ganglia of rabbit halved lengthwise, quartered ganglia of cat or small blocks of calf ganglion tissue (Roch & Kalix, 1975) were incubated for approx 30 min at 37°C in the solution which was kept saturated with the gas mixture; these conditions having been shown in rabbit (Kalix et al., 1974) to permit the ganglia to remain fully responsive to electrical stimulation. The samples were then transferred to vials containing the incubation medium to which either depolarizing substances, theophylline or both had been added; alternatively, part of the Na + was replaced by K ÷ and this solution was used both with and without the addition of theophylline. At the end of the incubation period, the tissue was denaturated, an extract was assayed for cAMP according to the method of Brown et al. (1971) and the amount of protein of the sample was determined by the method of Lowry et al. (1951). Details of these procedures have been previously described (Roch & Kalix, 1975). Veratridine and cevadine were obtained from Aldrich Chemicals, Milwaukee/USA; aconitine and delphinine from Fluka AG, Buchs/Switzerland; ouabain and theophylline from E. Merck AG, Darmstadt/Germany. RESULTS The c A M P concentration in untreated SCG tissue that h a d been equilibrated for approx 30rain in Locke solution, was found to range from 14.8 (calf) to 19.9 (rabbit) pmoles/mg of protein (Table 1). W h e n theophylline was added to the medium in order to prevent the breakdown of cAMP, a moderate increase in the basal c A M P concentration was observed, ranging from 54% (rabbit) to 77% (rat). Similar results
2(~S
P l m R KALIX ANt:' PHILIPI'I:! ROCH
l'ablc 1. Increases in cAMPconlcnt induced by depolarizing media and by theophylline m the superior cervical ganglion of different species
I
Rat
Locke
Theophylline
K+
(10-2M)
(10-1M)
plus
theophylline
Veratridine
plus
(10-2H)
(10-2M)
Cat
Calf
15.8
+ 2.5
(3;30)
19.9
+ 1.9
(9;30)
15.2
+ 5,2
(3;30)
14.8
+ 1.3
(17;30
27.9
+ 1.4
(3; 6)
30.6
+ 6.3
(3~
6)
24.0
+ l.l
(3;
23.7
+ i.0
{62;
58.9
+ 7.5
(3~
6)
68.7
+ 8.7
(3;
6)
18.5
+ 2.6
( 5; ~
112.4
+ 4.5
(3;
6)
168,6
+40.1
(3; 6)
68.5
+ 3.1
(37;
9
74.8
+ 8.7
(4;
24.8
+ 2.4
( 4;
9
252.5
~58.0
(3; 4)
76.5
~ 9.0
( 4;
Z
(5XI0-4M)
theophylline
Rabbit
165.6
+17.8
(3+
6)
43.7
+ 4,7
(3;
6)
6)
4)
38+0
+ 1.7
(3; 6)
9
Fhc basal cAMP concentration in the ganglia first line) was determined a~er a 30 min equilibration period in Locke solution. In parenthesis: number of experiments; minutes of incubation. Values* are taken from Roch & Kalix (1975), all values are expressed as pmoles cAMP per mg protein. (not shown) were obtained with other phosphodiesterase-inhibitors. Replacement of 100raM Na + of the incubation medium with K + resulted in a three- to four-fold increase of the c A M P level ill rat and rabbit ganglia, bnt in only a comparatively small increase in calf ganglia. On the other hand, when theophylline was present in b o t h the control and the test medium, the response of rat and rabbit ganglia to high K + was amplified by a factor of approx two, and that of calf ganglion tissue by a factor of a b o u t four. Cat ganglia, however, responded to potassium stimulation with
only a moderate increase in c A M P content even after addition of theophylline. In an analogous series of experiments, veratridine, a depolarizing alkaloid, was used to induce the rise of the ganglionic c A M P level. In general, its effects were found to be similar to those of high potassium. It is noteworthy that when the incubation medium contained veratridine, the species differences observed paralleled those described above for K +. In a previous study on calf ganglia (Kalix & Roch, 1975), the increase in ganglionic c A M P due to veratridine was found to be rapid and, in spite of the pres-
pmoles cAMP/ mg p r o t e i n 300 -
100
.~°
0
~
0
I
t 4
1 9
i 20 m i n i n c u b a t i o n
Fig. 1. Time course of the c A M P accumulation in rabbit SCG during exposure to solutions containing
10mM theophylline plus one of the following agents: 0.500mM veratridine II, 0.300mM cevadine D, 0.050 mM ouabain &, 0.500 mM aconitine II.
cAMP in superior cervical ganglion ence of theophylline, transient. In contrast, maximally effective doses of ouabain were shown to produce a much slower but sustained cAMP increase. In the present study, the same phenomenon was observed in similar experiments on rabbit ganglia (Fig. 1). In these ganglia, high concentrations of two other depolarizing alkaloids, i.e. aconitine and cevadine (a structural analogue of veratridine) were also found to cause an increase in cAMP content. Exposure of rabbit ganglia to solutions containing delphinine, an alkaloid pharmacologically similar to aconitine, for periods ranging from 1 to 20rain, caused no significant change in cAMP content.
269
observed might not also reflect species variations in the phosphodiesterase activity similar to those demonstrated above for bovine SCG. It should be mentioned, however, that the mechanism leading to increased cAMP synthesis in the cortex appears to differ from the one involved in the ganglion (Roch & Kalix, 19751. In rabbit ganglia, the cAMP accumulation induced by exposure to high potassium is comparable in magnitude to that induced by cholinomimetic stimulation; in this species, the cAMP level rises about two-fold upon exposure to carbachol alone, but fourfold when theophylline or other phosphodiesterase inhibitors are present during stimulation (Kalix et al., 1974). The two types of stimulation do not seem to DISCUSSION be interdependent, however, since neither a nicotinic The results described above lend support to the nor a muscarinic antagonist reduced the K +-induced assumption that depolarization-dependent cAMP ' cAMP increase in bovine SCG (Roch & Kalix, 1975). In all four species examined parallel experiments synthesis is of common occurrence in mammalian SCG. The basal cAMP concentration was found to were performed in which veratridine was used instead be approximately the same in the SCG of each of of high potassium, and the results were practically the four species examined and the values obtained the same. An identical time course pattern for the were similar to those reported in the literature for stimulating effect of veratridine and ouabain respectthe SCG of calf (Kebabian & Greengard, 1971), rat ively, previously reported for calf ganglia (Kalix & (Lindl & Cramer, 1974) and rabbit (McAfee et al., Roch, 1975), was observed in rabbit ganglion tissue 197l). In all four species, exposure of the ganglia to as well. Furthermore, in rabbit, as in calf, the cAMP theophylline resulted in a moderate rise in the level content which had been increased by exposure to veratridine, decreased after longer exposure in spite of of cAMP. In a previous paper, we have reported that the the high concentration of theophylline in the medium, cAMP level in calf SCG can be raised by exposing a peculiarity which cannot' be explained at present. the tissue to media containing high concentrations Aconitine and cevadine, two alkaloids with pharmaof K ÷ (Roch & Kalix, 1975). In the present exper- cological properties similar to those of veratridine, iments, depolarizing media were found to cause an were also seen to cause a cAMP increase in ganglion increase in cAMP concentration in three further spe- tissue. The capacity to induce depolarization would cies; rat, rabbit and cat. The cAMP increase in calf therefore seem to be the common characteristic of ganglion was found to be considerably smaller than these substances, responsible for the observed activation of cAMP synthesis. The present study demonthat observed in rat, rabbit or cat. The extent to which this response could be amplified by theophyl- strates that the mechanism of increased cAMP synline, on the other hand, was found to be greater in thesis is a consequence, probably indirect, of depolaricalf than in the other species. The observation that zation, is operative in the SCG of at least several high K ÷ and theophylline individually cause only mammalian species. relatively small increases, whereas their simultaneous Acknowledgement--The authors are grateful to Mrs. J. presence in the medium results in a comparatively Noebels for help with the English of the manuscript, large cAMP accumulation, might indicate that in calf, phosphodiesterase is activated by its substrate. This REFERENCES strong dependence of the cAMP accumulation on the presence of a phosphodiesterase-inhibitor appears to BROWN B., ALBANOJ., EK1NS R., SGHERZI A. & TAMPION be characteristic of bovine ganglion tissue since W. (1971) Saturation assay for cyclic AMP using endogenous binding protein. Biochem. J. 121, 561-562. marked increases in cAMP concentration without phosphodiesterase inhibition have been shown to CrIATZKELS., Z1MMERMANI. & BERG A. (1974) Modulation of cyclic AMP synthesis in the cat superior cervical occur in rat and rabbit. Comparable observations ganglion by short term presynaptic stimulation. Brain have been made in cerebral cortex slices, in this tissue Res. 80, 523 529. it was demonstrated that an accelerated conversion GREENGARD P. & KEBABIAN J. W. (1974).Role of cyclic of prelabelled ATP to cAMP can be caused by depoAMP in synaptic transmission in the mammalian perilarizing media (Shimizu & Daly, 1972). Both in this pheral nervous system. Fedn Proc. Fedn Am. Socs exp. and another study (Rail & Sattin, 1970) considerable Biol. 33, 1059-1067. species differences in the amplitude of the response KALIX P., McAFEE D., SCHORDERETM. & GREENGARDP. (1974) Pharmacological analysis of synaptically mediated were found. As these studies were conducted without increase in cyclic AMP in rabbit superior cervical gangconcomitant phosphodiesterase-inhibition, it would lion. J, Pharmac. exp. Ther. 188. 676-687. be of interest to determine whether the differences
270
P~iTER KALIX AND PHILIPPE ROCH
KAL1X P. & ROC'H PH. (1975) Effect of dcpolarizing agents on the adenosine-3',5'-monophosphate content of the bovine superior cervical ganglion. NawTv~7 Schmiedebo'~f Arch. Pharmac. 291, 131 137. KEnABIAN J. W. & GREENGARD P. (1971) Dopamine sensitive adenylate cyclase: possible role in synaptic transmission. Science, N.Y. 174, 1346 1349. LmET B. (1970)Generation of slow inhibitory and excitatory postsynaptic potentials. Fedn Proc. Fed, Am. Sots exp. Biol. 29, 1945 1956. L1NDL T, & CRAMER H. (1974) Formation. accumulation and release of cyclic A M P induced by histamine in the superior cervical ganglion of the rat i~ z:itro. Biochim. biophys. Acta 343, 182 191. LOWRY O., ROSEBROUGH N., FARR A & RANDALL R. (1951) Protein measurement with the Folin phenol reagent. J. biol. Chem. 193, 265-275.
Mc:AFLI D.. S('HORDERt