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SUPERSENSITIVITY TO ISOPROTERENOL AND A NEW ADRENERGIC β-MIMETIC AGENT TRIMETHOQUINOL* ON THE BLOOD PRESSURE OF THE RESERPINE TREATED RAT
SUPERSENSITIVITY TO ISOPROTERENOL AND A NEW ADRENERGIC 13-MIMETIC AGENT TRIMETHOQUINOL* ON THE BLOOD PRESSURE OF THE RESERPINE TREATED RAT HIKARU OZAWA, ISAO OTSUKI ANDYUKIKO SHIROISHI Department ofChemical Pharmacology, Pharmaceutical Institute, Tohoku University School ofMedicine, Sendai Received forpublication September 2, 1968 Supersensitivity to catecholamines in various organs after reserpine treatment has been reported by many investigators. Trendelenburg et al. (1) described that this action was associated with the impairment of uptake of catecholamines to adrenergic nerve terminals.
On the otherhand isoproterenol,one of the catecholamines, wasnot retainedby the heart (2). Neither cocaine(3) nor denervation(4) could cause'supersensitivity to this amine. However,Fleming et al. (5) reported that after reserpine'treatment the isolated ileum of rabbit becamemore sensitiveto isoproterenoland recentlyKhan et al. (6) also showed that on the isolated rat fundus strip preparation reserpine and guanethidine increased the sensitivity to isoproterenol. But further evidences for these phenomena were not obtained. In a previous paper (7) authors reported briefly that on the blood pressure of the rat treated with reserpine the hypotensive action of isoproterenol was potentiated. In order to confirm our previous results, the effects of reserpine on the sensitivity to isoproterenol and a new adrenergic Q-stimulating agent trimethoquinol (8) were studied on the blood pressure of the rat. METHODSAND MATERIALS Male albino rats of Wistar strain were anesthetized with urethane 1.0-1.6 g/kg by subcutaneous injection. The blood pressure was recorded from the carotid artery with a mercury manometer or electrotransducer. Schedules of pretreatment with reserpine were as follows : The dose was 2 mg/kg/day on the first two days and 1 mg/kg/day on the next two days were given subcutaneously prior the experiments. Isoproterenol and trimethoquinol were given intravenously in doses ranging from 0.001 to 1,000 pg/kg. Injections were made into jugular vein via cannulated polyethylene tube. Thisworkwas reportedat the KantoArea RegionalMeetingof the JapanesePharmacological Society, June 1, 1968. *1-1-(3 , 4, 5-Trimethoxybenzyl)-6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline HCl
Time intervals between injections were long enough to allow full recovery of blood pressure. The drugs used in this experiments were as follows: d-isoproterenol HCI, dl-isoprote renol HCI, l-isoproterenol HCI, d-l-(3, 4, 5-trimethoxybenzyl)-6,7-dihydroxy-1, 2, 3, 4 tetrahydroisoquinoline HCI (d-trimethoquinol), dl-1-(3, 4, 5-trimethoxybenzyl) -6,7-dihydro xy 1, 2, 3, 4-tetrahydroisoquinoline HCl (dl-trimethoquinol), 1-l-(3, 4, 5-trimethoxybenzyl) 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline HCl (trimethoquinol) and reserpine. All drugs were dissolved in physiological saline solution. Significance of difference between none treated groups and reserpine treated groups was estimated using `t" test (p<0.05). RESULTS
Effectsof reserpineon the depressorresponsesof isoproterenol a) dl-Isoproterenol As shown in Fig. 1, intravenous injection of 10, 50 and 100 ng/kg of dl-isoproterenol produced only a slight decrease of blood pressure in the control groups. But in the reser pine treated groups, even 5 ng/kg of dl-isoproterenol produced a decrease of blood pres sure about 30 mmHg or more. Fig. 2 shows the dose-response curve of dl-isoproterenol in the 7 of none and reserpine treated rats respectively. As can be seen in Fig. 2, the potentiation of hypotensive effect
FiG.1. Action of dl-isoproterenol in normal rat (above) and in the rat treated with reserpine 2 mg/kg/day for the first two days and 1 mg/kg/day for the next two days before experiments (below).
of dl-isoproterenol by reserpine was significant (p<0.05) at the doses from 0.03 beg/kg to 3 ug/kg. b) l-Isoproterenol In the case of 1-isoproterenol, it was observed that the hypotensive effect was partially potentiated by the treatment with reserpine (Fig. 3).
FIG. 2. Effect of reserpine on the depressor responses of dl-isoproterenol. N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of dl-isoproterenol
FIG.3. Effect of reserpine on the depressor responses of 1-isoproterenol. N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of 1-isoproterenol
FIG. 4. Effect
FIG.5. Effect of reserpine on the depressor responses of d1-1-(3,4,5-trimethoxybenzyl) 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquino line HC1 (dl-trimethoquinol). N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of dl-trimethoquinol
of reserpine
on
the
depres
responses of d-isoprotereno.l. N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of d-isoproterenol
c) d-Isoproterenol In the case of d-isoproterenol, it was observed that the hypotensive effect was not potentiated by the treatment with reserpine (Fig. 4). Effectof reserpineon the depressorresponsesof 1-(3, 4, 5-trimethoxybenzyl)-6,7-dihydroxy-1,2, 3, 4 Tetrahydroisoquinoline HCl a) dl Trimethoquinol Fig. 5 shows the dose-response curve of dl-isomer in the 7 of the none and reserpine treated rats respectively. As can be seen in Fig. 5, the potentiation of hypotensive effect of dl-isomer by reserpine was significant (p<0.05) at the doses from 1 ,ug/kg to 1,000 pg/kg. b) Trimethoquinol(1-isomer) In the case of trimethoquinol,
it was observed that the hypotensive effect was
partially potentiated by the treatment with reserpine (Fig. 6). c) d Trimethoquinol In the case of d-isomer, it was observed that the hypotensive effect was not poten tiated by the treatment with reserpine (Fig. 7). r
FIG.6. Effect of reserpine on the depressor responses of 1-1-(3,4,5-trimethoxybenzyl) 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquino line HC1 (trimethoquinol). N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of trimethoquinol
r%
J.IG.1. Ettect of reserpine on the depressor responses of d-1-(3,4,5-trimethoxybenzyl). 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquino line HC1 (d-trimethoquinol). N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of d-trimethoquinol
DISCUSSION In the present experiments, it was confirmed that reserpine increased the sensitivity to isoproterenol on the blood pressure of the rat. Moreover it was also observed that re serpine increased the sensitivity to a new adrenergic 8-stimulating agent trimethoquinol. These results were accorded with the recent observation of Fleming et al. (5) on the isolated
rabbit ileum preparation and of Khan et al. (6) on the isolated rat fundus strip preparation. They suggested that this might be the changes of sensitivity of the smooth muscle. From the results mentioned above, it is assumed that reserpine would enhance the sensitivity of the 9-receptor of the smooth muscle in the cardiovascular system. Among the optical isomers of these adrenergic (3-stimulating agents, the hypotensive effects of dl and 1-isomer were apparently potentiated by the treatment with reserpine but d-isomer was not affected. Thus, these results were in an accordance with the results on some isolated organs, in which the dl and 1-isomer were active and d-isomer was pharmacologically inactive as 8-stimulating agent (8). It has been supposed by Iversen (9) that the mechanism of potentiation of norepineph rine by cocaine was due to the inhibition of uptake of norepinephrine in the sympathetic nervous system. But as stated in the introduction, isoproterenol was hardly retained by the heart and authors also observed that cocaine failed to potentiate the sensitivity to iso proterenol on the isolated trachea preparation (10). So that the uptake theory of Iversen could not be applicable to explain the mechanism of potentiation to isoproterenol. The results of the present study would suggest that reserpine may increase the sensi tivity of (3-receptor to isoproterenol by the mechanism which is independent of the uptake of catecholamines in the sympathetic nervous system. SUMMARY The effects of reserpine on the sensitivity to isoproterenol and a new 9-mimetic agent trimethoquinol, 1-(3, 4, 5-trimethoxybenzyl)-6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline HC1, were studied in the blood pressure of the rat. The results obtained in this study would support the view that reserpine may increase the sensitivity of 0-receptor to isoproterenol by the mechanism which is independent of the uptake of catecholamines in the sympathetic nervous system. Acknowledgement: We are indebtedto Prof. S. Sugasawaand Dr. K. Abe of ResearchLaboratories, Tanabe PharmaceuticalCo., for kindly supply of trimethoquinol and its isomers, and to Nikken ChemicalCo., for kindly supply of isoproterenoland its isomers. REFERENCES 1) TRENDELENBURG, U.: Pharmac.Rev.18, 629 (1966) 2) HERTTING, G.: Biochem. Pharmac.13, 1119(1964) 3) MAXWELL, R.A., DANIELL, A.I., SHEPPARD, H. ANDZIMMERMAN, J.H.: J. Pharmac.exp.Ther.137, 31 (1962) 4) SMITH, C.B.: J. Pharmac. exp.Ther.142, 163 (1963) 5) FLEMING, W.W.ANDSCHMIDT, J.: J. Pharmac.exp.Ther.135,34 (1962) 6) KHAN,I. ANDASMAE, R.: LifeSci.7, 307 (1968) 7) OZAWA, H. AND MARUYAMA, Y.: Foliapharmac. jap. 61, 387 (1965)(in Japanese) 8) SATO,K., IWASAWA, Y. ANDKIYOMOTO, A.: Foliapharmac. jap. 64, 268 (1968) (in Japanese) 9) IVERSEN, L.L.: The Uptakeand Storageof Noradrenaline in Sympathetic Nerves,CambridgUniv. Press (1967) 10) Unpublisheddata
On the otherhand isoproterenol,one of the catecholamines, wasnot retainedby the heart (2). Neither cocaine(3) nor denervation(4) could cause'supersensitivity to this amine. However,Fleming et al. (5) reported that after reserpine'treatment the isolated ileum of rabbit becamemore sensitiveto isoproterenoland recentlyKhan et al. (6) also showed that on the isolated rat fundus strip preparation reserpine and guanethidine increased the sensitivity to isoproterenol. But further evidences for these phenomena were not obtained. In a previous paper (7) authors reported briefly that on the blood pressure of the rat treated with reserpine the hypotensive action of isoproterenol was potentiated. In order to confirm our previous results, the effects of reserpine on the sensitivity to isoproterenol and a new adrenergic Q-stimulating agent trimethoquinol (8) were studied on the blood pressure of the rat. METHODSAND MATERIALS Male albino rats of Wistar strain were anesthetized with urethane 1.0-1.6 g/kg by subcutaneous injection. The blood pressure was recorded from the carotid artery with a mercury manometer or electrotransducer. Schedules of pretreatment with reserpine were as follows : The dose was 2 mg/kg/day on the first two days and 1 mg/kg/day on the next two days were given subcutaneously prior the experiments. Isoproterenol and trimethoquinol were given intravenously in doses ranging from 0.001 to 1,000 pg/kg. Injections were made into jugular vein via cannulated polyethylene tube. Thisworkwas reportedat the KantoArea RegionalMeetingof the JapanesePharmacological Society, June 1, 1968. *1-1-(3 , 4, 5-Trimethoxybenzyl)-6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline HCl
Time intervals between injections were long enough to allow full recovery of blood pressure. The drugs used in this experiments were as follows: d-isoproterenol HCI, dl-isoprote renol HCI, l-isoproterenol HCI, d-l-(3, 4, 5-trimethoxybenzyl)-6,7-dihydroxy-1, 2, 3, 4 tetrahydroisoquinoline HCI (d-trimethoquinol), dl-1-(3, 4, 5-trimethoxybenzyl) -6,7-dihydro xy 1, 2, 3, 4-tetrahydroisoquinoline HCl (dl-trimethoquinol), 1-l-(3, 4, 5-trimethoxybenzyl) 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline HCl (trimethoquinol) and reserpine. All drugs were dissolved in physiological saline solution. Significance of difference between none treated groups and reserpine treated groups was estimated using `t" test (p<0.05). RESULTS
Effectsof reserpineon the depressorresponsesof isoproterenol a) dl-Isoproterenol As shown in Fig. 1, intravenous injection of 10, 50 and 100 ng/kg of dl-isoproterenol produced only a slight decrease of blood pressure in the control groups. But in the reser pine treated groups, even 5 ng/kg of dl-isoproterenol produced a decrease of blood pres sure about 30 mmHg or more. Fig. 2 shows the dose-response curve of dl-isoproterenol in the 7 of none and reserpine treated rats respectively. As can be seen in Fig. 2, the potentiation of hypotensive effect
FiG.1. Action of dl-isoproterenol in normal rat (above) and in the rat treated with reserpine 2 mg/kg/day for the first two days and 1 mg/kg/day for the next two days before experiments (below).
of dl-isoproterenol by reserpine was significant (p<0.05) at the doses from 0.03 beg/kg to 3 ug/kg. b) l-Isoproterenol In the case of 1-isoproterenol, it was observed that the hypotensive effect was partially potentiated by the treatment with reserpine (Fig. 3).
FIG. 2. Effect of reserpine on the depressor responses of dl-isoproterenol. N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of dl-isoproterenol
FIG.3. Effect of reserpine on the depressor responses of 1-isoproterenol. N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of 1-isoproterenol
FIG. 4. Effect
FIG.5. Effect of reserpine on the depressor responses of d1-1-(3,4,5-trimethoxybenzyl) 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquino line HC1 (dl-trimethoquinol). N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of dl-trimethoquinol
of reserpine
on
the
depres
responses of d-isoprotereno.l. N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of d-isoproterenol
c) d-Isoproterenol In the case of d-isoproterenol, it was observed that the hypotensive effect was not potentiated by the treatment with reserpine (Fig. 4). Effectof reserpineon the depressorresponsesof 1-(3, 4, 5-trimethoxybenzyl)-6,7-dihydroxy-1,2, 3, 4 Tetrahydroisoquinoline HCl a) dl Trimethoquinol Fig. 5 shows the dose-response curve of dl-isomer in the 7 of the none and reserpine treated rats respectively. As can be seen in Fig. 5, the potentiation of hypotensive effect of dl-isomer by reserpine was significant (p<0.05) at the doses from 1 ,ug/kg to 1,000 pg/kg. b) Trimethoquinol(1-isomer) In the case of trimethoquinol,
it was observed that the hypotensive effect was
partially potentiated by the treatment with reserpine (Fig. 6). c) d Trimethoquinol In the case of d-isomer, it was observed that the hypotensive effect was not poten tiated by the treatment with reserpine (Fig. 7). r
FIG.6. Effect of reserpine on the depressor responses of 1-1-(3,4,5-trimethoxybenzyl) 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquino line HC1 (trimethoquinol). N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of trimethoquinol
r%
J.IG.1. Ettect of reserpine on the depressor responses of d-1-(3,4,5-trimethoxybenzyl). 6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquino line HC1 (d-trimethoquinol). N : none treated group R : reserpine treated group s : significant (p<0.05) Ordinate : fall of blood pressure Abscissa : dose of d-trimethoquinol
DISCUSSION In the present experiments, it was confirmed that reserpine increased the sensitivity to isoproterenol on the blood pressure of the rat. Moreover it was also observed that re serpine increased the sensitivity to a new adrenergic 8-stimulating agent trimethoquinol. These results were accorded with the recent observation of Fleming et al. (5) on the isolated
rabbit ileum preparation and of Khan et al. (6) on the isolated rat fundus strip preparation. They suggested that this might be the changes of sensitivity of the smooth muscle. From the results mentioned above, it is assumed that reserpine would enhance the sensitivity of the 9-receptor of the smooth muscle in the cardiovascular system. Among the optical isomers of these adrenergic (3-stimulating agents, the hypotensive effects of dl and 1-isomer were apparently potentiated by the treatment with reserpine but d-isomer was not affected. Thus, these results were in an accordance with the results on some isolated organs, in which the dl and 1-isomer were active and d-isomer was pharmacologically inactive as 8-stimulating agent (8). It has been supposed by Iversen (9) that the mechanism of potentiation of norepineph rine by cocaine was due to the inhibition of uptake of norepinephrine in the sympathetic nervous system. But as stated in the introduction, isoproterenol was hardly retained by the heart and authors also observed that cocaine failed to potentiate the sensitivity to iso proterenol on the isolated trachea preparation (10). So that the uptake theory of Iversen could not be applicable to explain the mechanism of potentiation to isoproterenol. The results of the present study would suggest that reserpine may increase the sensi tivity of (3-receptor to isoproterenol by the mechanism which is independent of the uptake of catecholamines in the sympathetic nervous system. SUMMARY The effects of reserpine on the sensitivity to isoproterenol and a new 9-mimetic agent trimethoquinol, 1-(3, 4, 5-trimethoxybenzyl)-6, 7-dihydroxy-1, 2, 3, 4-tetrahydroisoquinoline HC1, were studied in the blood pressure of the rat. The results obtained in this study would support the view that reserpine may increase the sensitivity of 0-receptor to isoproterenol by the mechanism which is independent of the uptake of catecholamines in the sympathetic nervous system. Acknowledgement: We are indebtedto Prof. S. Sugasawaand Dr. K. Abe of ResearchLaboratories, Tanabe PharmaceuticalCo., for kindly supply of trimethoquinol and its isomers, and to Nikken ChemicalCo., for kindly supply of isoproterenoland its isomers. REFERENCES 1) TRENDELENBURG, U.: Pharmac.Rev.18, 629 (1966) 2) HERTTING, G.: Biochem. Pharmac.13, 1119(1964) 3) MAXWELL, R.A., DANIELL, A.I., SHEPPARD, H. ANDZIMMERMAN, J.H.: J. Pharmac.exp.Ther.137, 31 (1962) 4) SMITH, C.B.: J. Pharmac. exp.Ther.142, 163 (1963) 5) FLEMING, W.W.ANDSCHMIDT, J.: J. Pharmac.exp.Ther.135,34 (1962) 6) KHAN,I. ANDASMAE, R.: LifeSci.7, 307 (1968) 7) OZAWA, H. AND MARUYAMA, Y.: Foliapharmac. jap. 61, 387 (1965)(in Japanese) 8) SATO,K., IWASAWA, Y. ANDKIYOMOTO, A.: Foliapharmac. jap. 64, 268 (1968) (in Japanese) 9) IVERSEN, L.L.: The Uptakeand Storageof Noradrenaline in Sympathetic Nerves,CambridgUniv. Press (1967) 10) Unpublisheddata