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Prolongation and potentiation of oxotremorine effects by desmethylimipramine, an “anti-tremorine” drug
Life Sciences Vol. 4, pp. 1031-1038, 1985. Great Britain.
Pergamon Press Ltd. Printed in
PBOIANC~ATIQi AND POTSIITLITION OP OEOTB$M08IIIE EFFBCTS BY DBSMBTHYLIIßPBAèIINS, AN "ANTI-TBSlDBINEM DßII(~ Folks Sjögvist** sad James Gillette Laboratory of Chemical Pharmacology, National Heart Institute, National Institutes of Health, Bathesda 14, Maryland
(Received 15 March 1985) TBâ!!4$INB, 1,4-dipyrrolidiao-2 butyne (TMN), induces both central a~ peripheral cholinergic effects in eaparimental animals .
Since the central affects
resemble some of the symptoms seen in Parkinson's disease, e .g . atazia, tremor, and rigidity, and can be blocked by manq drugs which are clinically useful in this disorder, Evaratt et al . (2) have suggested tramorina ae a tool is screening compounds for anti-Parkinson activity .
T!N is now also commonly used in
the search for drugs with central anticholinergic properties . The cholinergic effects of TM1, however, are mediated through the formation of ozotremorine (OT!!i), and sot by the parent compound itself (3,4,5) . Thus, true anticholinergic drugs should block the effects of both TMN and O'II~li. But, as sham in this paper, desmethylimipramina (D1ß), which is kaam to antagonize the pharmacological actions of tremorine (6,10), potantiates and prolongs the action of ozotremorine .
Our findings suggest that DMI couataracté
the effects of TMN by decelerating the formation of 01?!d and enhances the action of OTMN by inhibiting its inactivation . Methods Male Sprague-Dawley rata (180-200 g) ware pretreated by intraperitoneal administration of SIQ+ 525A (ß-diethylaminocthyl dipheaylpropylacetate, 50 mg/kg), *A preliminary report of this work has appeared (1) . **Present Address :
Division of Clinical Pharmacology, Department of Medicine, Johns Hopkins IIniversity, Baltimore, Maryland .
1031
1032
OIiOTREMORINE EFFECTS
Vol . 4, No. 10
D!Q (deamethylimipramine hydrochloride 10-40 mg/kg), atropine sulphate (0 .5-2 mg/kg) or saline 30 minutes before injection of T!N (tremorine hydrochloride 10 mg/kg,
i.p .) or OT!!i (ozotramorina,
base, i .p .) .
corresponding to 0.3 mg/kg of the free
The onset and duration of visible tremor was then determined by
an obaerper kept unaware of the type of pretreatment used .
The intensity of
tremors and lacrimation was determined by an arbitrary scoring procedure ae defined in Tables 1 .
Statistical comparisons were made using Student's t-teat . Reaulta
Data in Table 1 show that Dl~ and SRF 525A decrease the intensity of the T1l~=syndrome but enhance the OTtâa-syndrome .
Thus, 10 minutes after administra-
tion of TM~1, the rats pretreated with DèII or
Sam+
the TlIIi effects .
Bowevar,
525A showed few,
if any, of
35 minutes later these animals showed more pronounced
symptoms than did the animals receiving Tlßi alone.
Ia contrast, OTMi caused
greater cholinergic effects is the rats pretreated with DMI or S&F 525A than in the controls, whether the animals were observed 10 minutes or 45 minutes after the injection of OTt4~1 .
!loreover, OT!!i killed many of the animals pretreated
with larger doses of DiII (40 mg/kg,
i.p .) . TABLE 1
Influence of Drugs oa the Effects of Tremori~e (TMi) and Ozotremoriaa (OT!!i) in Rate Pretreatment (30 min. i.p .) Saline Dlü* 40 mg/kg SKF 525A 50 Saline S~ 525A *D~lü ~ **Tlhl ~ ~k~0~~.
Treatment i .p .
OTMi***
50 " deamathylimipramine 10 mg/kg p .3 mg~kg
N 10 10 10 15
Iatanait Tremors 10 45 ++ (+) 0 + + + + 0
of S~~atomsy Lacrimation 10 45' +(+) 0 (+) 0 0 0 0 +
9 ++ + + ++ + Definition of acorea : 0 ~ ao visible tremor or lacriwation + ~ visible tremor or lacrimatioa ++ ~ pronounced incapacitating tremor, copious lacrimation
1To avoid bias in the scoring procedure the observer was kept unaware of the pretreatment used .
OXOTREMORINE EFFECTS
Vol. 4, No . 10
1035
As shown in Table 2, both D!!I and SiQ+ 525A significantly (P ~ 0 .001) delay the onset of action of TMÜ and hasten that of O'lili .
Moreover, both compounds
significantly (P ~ 0.001) prolong the action of both TMN and 011tî . small doses of atropine (0 .5 mg/kg,
In contrast,
i.p .) slightly delay the onset of both
Ttti and O'IIti effects and markedly shorten their duration ; larger doses (~ 1 mg/kg) completely prevent the observable effects of both TMN and OT!!~ . Thus, the effect of DMI on the TMN and Oüti syadromea resembles the action of SRF 525A rather thaw that of atropine . TABLE 2 Bffect of Drugs on Onset and Duration of Tremorine (T!N) and Osotremorine (O1?s1) Syndromes in Rata Pretreatment (30 min. i.p .)
Treatment (i .p .)
N
Onset of Tremors (min . t S.B .)
Saline DMI 40 mg/kg SBF 525A 50 mg/kg
TMN* " "
10 10 10
4.7 ~ 0 .4 18 .3 t 1 .7 18 .5 t 5 .5
Saline Atropine 0.5 mg/kg
TMN* "
8 8
5 .1 t 0 .5 5 .8 t 0 .9
Saline DMI 20 mg/kg DMI 40 mg/kg SRF 525A 50 mg/kg
OTMN** " " "
Saline Atropine 0 .5 mg/kg
OTMN** "
10 9 10*** 9
I
8 8
4 .3 2 .8 2 .9 2.0
I
t t t t
Duration of Tremors (min . t S.S .) 48 .5 t 4.5 105 3 11 .5 159 t 13 .4 42 .3 t 15 .4 t
0.5 0.1 0.3 0.5
3.2 t 0 .4 4.9 1 0.2
32 .5 58 .3 106 104
I
4.6 2.5
t 3.8 t 6 .1 t 15 .5 t 10 .6
29 .3 t 13 .3 1
2.2 1 .1
*TI4i ~ 10 mg/kg **OTMN ~ 0.3 mg/kg ***2/10 died The finding that DMI and SRF 525A potentiated a~ prolonged the action of 011ßd suggested that their apparent antitramorine affect was due entirely to the delay in onset of the TIl~i syndrome and not to a blockade of choliaergic recep for sites.
Accordingly, when rats were pretreated with TMN and then given DMI
(10-40 mg/kg,
i .p .) or Slü+ 525A (25-50 mg/kg,
i .p .) oa appearance of the tremors,
1034
OROTREMORINE EFFECTS
Vol. 4, No. 10
the syndrome was enhanced as well as prolonged (N ~ 10) .
The delay in onset of
action of TMd is presumably caused by a decrease in formation of 01Md by liver microsomal ensymas.
idelch and Hocsis (3) have shown that SA+ 525~A inhibits the
formation of "activated" T!!d by liver preparations, and SjHgviat et al . (7) found that of the many metabolites of,TlN formed by rat liver preparations, only OT!!d produces tremors when iajectad intracerebrally into mice . D~lII sad SNF 52SA grobably do not enhance the effects of OTMd by potentia~ tion of cholinergic receptor sites or by altering the distribution of O1Md is tissues .
1~ and SBF 525A cause no reappearance of the O'II~ld syndrome when
iajacted intravenously immediately after the OTMd effects have vanished (N ~ 10). Moreover, pretreatment of rata with D1ß or SSI+ 525A does not appreciably affect the iataneity of the syndrome induced by intravenous threshold doses of 01?Qi (N ~ 10), but markedly enhances the effects of threshold doses of O'i4Si given intraperitoneally (N ~ 10) .
Finally,
the effects of 01!ßd injected intracere-
brally into mice are not changed by pretreatment with DMI (40-60 mg/kg,
s .c .) .
These findings suggest that DMI and SRF 525A potentiate and prolong the effects of 0'B!d by inhibiting its conversion to pharmacologically inactive metabolites . In support of this view, the administration of D1ß to rate (20-40 mg/kg, decreases the metabolism of OTMtd by liver preparations
i.p .)
(7) .
Discuseioa The anti-tremorina" effect of DMI has hitherto bean thought to reflect a central anticholinergic property (6) . concept,
Our data, however, do not support this
sine Diß, unlike atropina," does not block the effects of OT!!d.
over, large doses of D1ß in mice (40-60 mg/kg,
More
s .c .) do not prevent central
cholinergic affects following intracerebral injections of d1Md,DFP and carbachol (unpublished observations) .
Furthermore, recent observations oa the mouse
pupil also contradict the view that DMI has any important central atropine-like property (10) .
These studies, therefore,
land no support to the view that the
antidepressant action of imipramine-like drugs is partially caused by a central anticholinergic effect
(Cf. 8,9) .
Vol. 4, No. 10
1035
OXOTREMORIIdE EFFECTS
Our data call for reiatnrpretatioa of some pravioua studiaa is which T!!f has bean used as a pharmacological tool,
for there is avideacn that other
anti-ttemoria~ drugs may aznrt their action by blocking the formation of O'II~i . Por ezample,
Sch 5706 (the diathylasinoathyl amide of monooathylethylphenyl-
malonate) and Sch 5705 (the diathylaminoethyl ester of monoathyl-ethylphanylmalonata) have base suggested in the therapy of.Parkinaon'a disease, because they were thought to counteract the T!!~-ey~rome solely at receptor sites (Cf. 11,12) .
We have found that these compounds azert interactions with 1Tl1
~ad OT!!i siuilar to those observed with D!II (13) .
Certain quaternary phnno-
thiaainas, which presumably do not pass the blood-brain barrier to any great erteat, have naverthalass been claimed to counteract the cholinnrgic nffncta of T!!i by a central action (14) .
It seems more likely that these compou~s
interfere with the formation of OT!!1,
since other phenothiasiaes such as
pro-
chlorperasine inhibit the affects of T!!i but not those of OTlPi in mica (15) . thus, Ttli metabolism may ba inhibited by several types of drugs which obviously do not necessarily have anticholinergic activity . Chronic treatment of aaimals with drugs may also influence the action of TlRi .
Pretreatment of rats with phanobarbital for several days hastens the
onset of action of Ttst, presumably by accelerating the formation of OT!!i by liver microsomes (J .J . Burns,
personal oommunication) .
On the other hand, pica
given T1+1~ for several days develop tolerance to T!!1 (16) but not to OliPi (13), suggesting that the conversion of T!!i to OTlN is decelerated is these animals . These findings arses the importance of elucidating the mechanise of actin of "anti-tramorine" drugs before they are claimed to be aaticholinergic or potentially useful in the treatment of Parkinson's disease. Açlmo~ledgmants The authors wish to eztend their appreciation to Dr . (;uy Svaratt, Abbott Laboratories, Horth Chicago,
I11 .,
for a gift of tramorina; to Dr . Donald J.
Jenden, IIniveraity of California, Los Angalea,
for a sample of omotraaorine ;
1038
O7COTREMORIIdE EFFECTS
Vol. 4, No. 10
sad to D~ . Earl Brimings, Geigy Research Laboratories, Yonlcars, N . Y ., for a gift of dnsmathylimipramiae . Bafereacee
6
1.
F . SdÔQVIBT and J .B . G Tt-~-~~ , Pharmscolostist
2 (1964) .
2.
G .M. SVBltETT, L .E . BLOCEAS and LIi. .BHSPPBBD, Scieaca ~ 79 (1956) .
3.
B .K. WELCS and J . EOCSIS, Ptoc . Soc . Ezp . Biol ., N .Y . 1~ 731 (1961) .
4.
A .Y. CHO, ü .L . HASLET'P and D .J . .~EN, Biocham. Biophys . Sae . Cow.
5
276 (1961) . 5.
8 . GE08GS, A .L . HIlSLE1T and D .J . JENDEN, Life Sci . ~ 361 (1962) .
6.
W. THSO~HALD, 0 . BULCH, S .A . EDNZ, C . l~POBGO, E .G . STENGEB aad G . ifiL~2Q èrch . Eat . Pharmacodyn . ~ 560 (1964) .
7.
F . SJÖQVIST, H . SCHIJMSCHSB sad J .B . GILLETTE, in preparation .
8.
K. FIIiE, Caned . Psychiat . Ass . J . ~ 5166 (1959) .
9.
0. BSNESOVA and I . TBINEßOVA, Biochem. Pharmacol . Suppl . 12, 57 (1963) .
10 .
G . ~~-t-~T-, 8 .1i. Q[TI1D1 and F .E . iiII.ï.IAIB, Brit . J . Pharmacol . ~ 330 (1964) .
11 .
P. PBEZIOSI aad G .B . DE VLEBSCIIOOÜER, Arch . Eat . Pharmacodyn . ~ 108 (1959) .
12 .
B . BOSEOVIC, 8 . PBZIC and P . STSBN, Mad . E~ . ~ 234 (1961) .
13 .
F . SJôQVLST and J .B . GTt-T-irrmR, uapublished observations .
14 .
D . LSNEE, Aranaimittal Forsch . 1 874 (1964) .
15 .
G .B . LESLIE and D .B . I91~iBi.L, Natura 202 . 97 (1964) .
16 .
L . DECSI, K . VABSZEGI and J . MEHES, J . Pharm . Lund . 1 127 (1961) .
Pergamon Press Ltd. Printed in
PBOIANC~ATIQi AND POTSIITLITION OP OEOTB$M08IIIE EFFBCTS BY DBSMBTHYLIIßPBAèIINS, AN "ANTI-TBSlDBINEM DßII(~ Folks Sjögvist** sad James Gillette Laboratory of Chemical Pharmacology, National Heart Institute, National Institutes of Health, Bathesda 14, Maryland
(Received 15 March 1985) TBâ!!4$INB, 1,4-dipyrrolidiao-2 butyne (TMN), induces both central a~ peripheral cholinergic effects in eaparimental animals .
Since the central affects
resemble some of the symptoms seen in Parkinson's disease, e .g . atazia, tremor, and rigidity, and can be blocked by manq drugs which are clinically useful in this disorder, Evaratt et al . (2) have suggested tramorina ae a tool is screening compounds for anti-Parkinson activity .
T!N is now also commonly used in
the search for drugs with central anticholinergic properties . The cholinergic effects of TM1, however, are mediated through the formation of ozotremorine (OT!!i), and sot by the parent compound itself (3,4,5) . Thus, true anticholinergic drugs should block the effects of both TMN and O'II~li. But, as sham in this paper, desmethylimipramina (D1ß), which is kaam to antagonize the pharmacological actions of tremorine (6,10), potantiates and prolongs the action of ozotremorine .
Our findings suggest that DMI couataracté
the effects of TMN by decelerating the formation of 01?!d and enhances the action of OTMN by inhibiting its inactivation . Methods Male Sprague-Dawley rata (180-200 g) ware pretreated by intraperitoneal administration of SIQ+ 525A (ß-diethylaminocthyl dipheaylpropylacetate, 50 mg/kg), *A preliminary report of this work has appeared (1) . **Present Address :
Division of Clinical Pharmacology, Department of Medicine, Johns Hopkins IIniversity, Baltimore, Maryland .
1031
1032
OIiOTREMORINE EFFECTS
Vol . 4, No. 10
D!Q (deamethylimipramine hydrochloride 10-40 mg/kg), atropine sulphate (0 .5-2 mg/kg) or saline 30 minutes before injection of T!N (tremorine hydrochloride 10 mg/kg,
i.p .) or OT!!i (ozotramorina,
base, i .p .) .
corresponding to 0.3 mg/kg of the free
The onset and duration of visible tremor was then determined by
an obaerper kept unaware of the type of pretreatment used .
The intensity of
tremors and lacrimation was determined by an arbitrary scoring procedure ae defined in Tables 1 .
Statistical comparisons were made using Student's t-teat . Reaulta
Data in Table 1 show that Dl~ and SRF 525A decrease the intensity of the T1l~=syndrome but enhance the OTtâa-syndrome .
Thus, 10 minutes after administra-
tion of TM~1, the rats pretreated with DèII or
Sam+
the TlIIi effects .
Bowevar,
525A showed few,
if any, of
35 minutes later these animals showed more pronounced
symptoms than did the animals receiving Tlßi alone.
Ia contrast, OTMi caused
greater cholinergic effects is the rats pretreated with DMI or S&F 525A than in the controls, whether the animals were observed 10 minutes or 45 minutes after the injection of OTt4~1 .
!loreover, OT!!i killed many of the animals pretreated
with larger doses of DiII (40 mg/kg,
i.p .) . TABLE 1
Influence of Drugs oa the Effects of Tremori~e (TMi) and Ozotremoriaa (OT!!i) in Rate Pretreatment (30 min. i.p .) Saline Dlü* 40 mg/kg SKF 525A 50 Saline S~ 525A *D~lü ~ **Tlhl ~ ~k~0~~.
Treatment i .p .
OTMi***
50 " deamathylimipramine 10 mg/kg p .3 mg~kg
N 10 10 10 15
Iatanait Tremors 10 45 ++ (+) 0 + + + + 0
of S~~atomsy Lacrimation 10 45' +(+) 0 (+) 0 0 0 0 +
9 ++ + + ++ + Definition of acorea : 0 ~ ao visible tremor or lacriwation + ~ visible tremor or lacrimatioa ++ ~ pronounced incapacitating tremor, copious lacrimation
1To avoid bias in the scoring procedure the observer was kept unaware of the pretreatment used .
OXOTREMORINE EFFECTS
Vol. 4, No . 10
1035
As shown in Table 2, both D!!I and SiQ+ 525A significantly (P ~ 0 .001) delay the onset of action of TMÜ and hasten that of O'lili .
Moreover, both compounds
significantly (P ~ 0.001) prolong the action of both TMN and 011tî . small doses of atropine (0 .5 mg/kg,
In contrast,
i.p .) slightly delay the onset of both
Ttti and O'IIti effects and markedly shorten their duration ; larger doses (~ 1 mg/kg) completely prevent the observable effects of both TMN and OT!!~ . Thus, the effect of DMI on the TMN and Oüti syadromea resembles the action of SRF 525A rather thaw that of atropine . TABLE 2 Bffect of Drugs on Onset and Duration of Tremorine (T!N) and Osotremorine (O1?s1) Syndromes in Rata Pretreatment (30 min. i.p .)
Treatment (i .p .)
N
Onset of Tremors (min . t S.B .)
Saline DMI 40 mg/kg SBF 525A 50 mg/kg
TMN* " "
10 10 10
4.7 ~ 0 .4 18 .3 t 1 .7 18 .5 t 5 .5
Saline Atropine 0.5 mg/kg
TMN* "
8 8
5 .1 t 0 .5 5 .8 t 0 .9
Saline DMI 20 mg/kg DMI 40 mg/kg SRF 525A 50 mg/kg
OTMN** " " "
Saline Atropine 0 .5 mg/kg
OTMN** "
10 9 10*** 9
I
8 8
4 .3 2 .8 2 .9 2.0
I
t t t t
Duration of Tremors (min . t S.S .) 48 .5 t 4.5 105 3 11 .5 159 t 13 .4 42 .3 t 15 .4 t
0.5 0.1 0.3 0.5
3.2 t 0 .4 4.9 1 0.2
32 .5 58 .3 106 104
I
4.6 2.5
t 3.8 t 6 .1 t 15 .5 t 10 .6
29 .3 t 13 .3 1
2.2 1 .1
*TI4i ~ 10 mg/kg **OTMN ~ 0.3 mg/kg ***2/10 died The finding that DMI and SRF 525A potentiated a~ prolonged the action of 011ßd suggested that their apparent antitramorine affect was due entirely to the delay in onset of the TIl~i syndrome and not to a blockade of choliaergic recep for sites.
Accordingly, when rats were pretreated with TMN and then given DMI
(10-40 mg/kg,
i .p .) or Slü+ 525A (25-50 mg/kg,
i .p .) oa appearance of the tremors,
1034
OROTREMORINE EFFECTS
Vol. 4, No. 10
the syndrome was enhanced as well as prolonged (N ~ 10) .
The delay in onset of
action of TMd is presumably caused by a decrease in formation of 01Md by liver microsomal ensymas.
idelch and Hocsis (3) have shown that SA+ 525~A inhibits the
formation of "activated" T!!d by liver preparations, and SjHgviat et al . (7) found that of the many metabolites of,TlN formed by rat liver preparations, only OT!!d produces tremors when iajectad intracerebrally into mice . D~lII sad SNF 52SA grobably do not enhance the effects of OTMd by potentia~ tion of cholinergic receptor sites or by altering the distribution of O1Md is tissues .
1~ and SBF 525A cause no reappearance of the O'II~ld syndrome when
iajacted intravenously immediately after the OTMd effects have vanished (N ~ 10). Moreover, pretreatment of rata with D1ß or SSI+ 525A does not appreciably affect the iataneity of the syndrome induced by intravenous threshold doses of 01?Qi (N ~ 10), but markedly enhances the effects of threshold doses of O'i4Si given intraperitoneally (N ~ 10) .
Finally,
the effects of 01!ßd injected intracere-
brally into mice are not changed by pretreatment with DMI (40-60 mg/kg,
s .c .) .
These findings suggest that DMI and SRF 525A potentiate and prolong the effects of 0'B!d by inhibiting its conversion to pharmacologically inactive metabolites . In support of this view, the administration of D1ß to rate (20-40 mg/kg, decreases the metabolism of OTMtd by liver preparations
i.p .)
(7) .
Discuseioa The anti-tremorina" effect of DMI has hitherto bean thought to reflect a central anticholinergic property (6) . concept,
Our data, however, do not support this
sine Diß, unlike atropina," does not block the effects of OT!!d.
over, large doses of D1ß in mice (40-60 mg/kg,
More
s .c .) do not prevent central
cholinergic affects following intracerebral injections of d1Md,DFP and carbachol (unpublished observations) .
Furthermore, recent observations oa the mouse
pupil also contradict the view that DMI has any important central atropine-like property (10) .
These studies, therefore,
land no support to the view that the
antidepressant action of imipramine-like drugs is partially caused by a central anticholinergic effect
(Cf. 8,9) .
Vol. 4, No. 10
1035
OXOTREMORIIdE EFFECTS
Our data call for reiatnrpretatioa of some pravioua studiaa is which T!!f has bean used as a pharmacological tool,
for there is avideacn that other
anti-ttemoria~ drugs may aznrt their action by blocking the formation of O'II~i . Por ezample,
Sch 5706 (the diathylasinoathyl amide of monooathylethylphenyl-
malonate) and Sch 5705 (the diathylaminoethyl ester of monoathyl-ethylphanylmalonata) have base suggested in the therapy of.Parkinaon'a disease, because they were thought to counteract the T!!~-ey~rome solely at receptor sites (Cf. 11,12) .
We have found that these compounds azert interactions with 1Tl1
~ad OT!!i siuilar to those observed with D!II (13) .
Certain quaternary phnno-
thiaainas, which presumably do not pass the blood-brain barrier to any great erteat, have naverthalass been claimed to counteract the cholinnrgic nffncta of T!!i by a central action (14) .
It seems more likely that these compou~s
interfere with the formation of OT!!1,
since other phenothiasiaes such as
pro-
chlorperasine inhibit the affects of T!!i but not those of OTlPi in mica (15) . thus, Ttli metabolism may ba inhibited by several types of drugs which obviously do not necessarily have anticholinergic activity . Chronic treatment of aaimals with drugs may also influence the action of TlRi .
Pretreatment of rats with phanobarbital for several days hastens the
onset of action of Ttst, presumably by accelerating the formation of OT!!i by liver microsomes (J .J . Burns,
personal oommunication) .
On the other hand, pica
given T1+1~ for several days develop tolerance to T!!1 (16) but not to OliPi (13), suggesting that the conversion of T!!i to OTlN is decelerated is these animals . These findings arses the importance of elucidating the mechanise of actin of "anti-tramorine" drugs before they are claimed to be aaticholinergic or potentially useful in the treatment of Parkinson's disease. Açlmo~ledgmants The authors wish to eztend their appreciation to Dr . (;uy Svaratt, Abbott Laboratories, Horth Chicago,
I11 .,
for a gift of tramorina; to Dr . Donald J.
Jenden, IIniveraity of California, Los Angalea,
for a sample of omotraaorine ;
1038
O7COTREMORIIdE EFFECTS
Vol. 4, No. 10
sad to D~ . Earl Brimings, Geigy Research Laboratories, Yonlcars, N . Y ., for a gift of dnsmathylimipramiae . Bafereacee
6
1.
F . SdÔQVIBT and J .B . G Tt-~-~~ , Pharmscolostist
2 (1964) .
2.
G .M. SVBltETT, L .E . BLOCEAS and LIi. .BHSPPBBD, Scieaca ~ 79 (1956) .
3.
B .K. WELCS and J . EOCSIS, Ptoc . Soc . Ezp . Biol ., N .Y . 1~ 731 (1961) .
4.
A .Y. CHO, ü .L . HASLET'P and D .J . .~EN, Biocham. Biophys . Sae . Cow.
5
276 (1961) . 5.
8 . GE08GS, A .L . HIlSLE1T and D .J . JENDEN, Life Sci . ~ 361 (1962) .
6.
W. THSO~HALD, 0 . BULCH, S .A . EDNZ, C . l~POBGO, E .G . STENGEB aad G . ifiL~2Q èrch . Eat . Pharmacodyn . ~ 560 (1964) .
7.
F . SJÖQVIST, H . SCHIJMSCHSB sad J .B . GILLETTE, in preparation .
8.
K. FIIiE, Caned . Psychiat . Ass . J . ~ 5166 (1959) .
9.
0. BSNESOVA and I . TBINEßOVA, Biochem. Pharmacol . Suppl . 12, 57 (1963) .
10 .
G . ~~-t-~T-, 8 .1i. Q[TI1D1 and F .E . iiII.ï.IAIB, Brit . J . Pharmacol . ~ 330 (1964) .
11 .
P. PBEZIOSI aad G .B . DE VLEBSCIIOOÜER, Arch . Eat . Pharmacodyn . ~ 108 (1959) .
12 .
B . BOSEOVIC, 8 . PBZIC and P . STSBN, Mad . E~ . ~ 234 (1961) .
13 .
F . SJôQVLST and J .B . GTt-T-irrmR, uapublished observations .
14 .
D . LSNEE, Aranaimittal Forsch . 1 874 (1964) .
15 .
G .B . LESLIE and D .B . I91~iBi.L, Natura 202 . 97 (1964) .
16 .
L . DECSI, K . VABSZEGI and J . MEHES, J . Pharm . Lund . 1 127 (1961) .