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From the National Iustitute of Mental Healih Addietion Research Ceuter U.S. Publie Health Service liospital Lexington, Kentucky, U.S.A. Cross Tolerance hetweeu Mesealine and LSD-25 With a Comparison of the Mesealine and LSD Reartions

by A, B. Wm, JR., HRs IsuELL and E. J, MtNER With 2 Figures in the Text -4 (Reczired Nocrmber S. 1961)

Althouglh sone differences have been reported. the rvactions produced in mían by the diethylainide of lysergie acid (LSD-25) ani mescalite seem very similar. Both drugs eause autonomie stimulation manifestedl by increased pupillary size, inerease in puise rate and blood pressure, and elevation of body temperature (BALESTaIERI and FoNNAR; B. NAN; HoH et al.; IsLL et al., 1956; SroNGs; STOLL). Both erate anxiety, difficulty in coneentration and thinking, flight of ideas, flue. tuations in mood, pereeptual distortion in all sensory modalities, trueand pseudo-hailucinations usually of visual nature. and depersonalizatin ( et al.; ; ; G nd M-LAY; HocH et ai.; IsELL ef al., 1956; MYER-GROSS; RIyKL et al.; SrockiNos; SroLL). Some authors have referred to the mental state induced by either agents as "experimental schizophrenia" (RINKEL et al; SG). ; .

The clinical resemblance of the syndromes eaused by mescaline and LSD-25 suggest that these drugs, despite differences in cheniical structure, eithier share a comuon mechanism of action or aet on final common pathway. This hypothesis is strengthened by reports of cross tolerance betwen the tw dugs (BLESTR, 1957, 1960; BLESE and FONTANARI). FUNTAXARI).

The purposes of this paper are: (l) to present a qunntitative comparison of the effects of LSD-25 and mescaline in the same subjeets; aui (2) to show, in confirmation of BALESTR1ER1 (1957 und 1960) and BLE. sTRiERt and FoNTaNARr, that direct tolorance develops to mesealine. and that subjeets tolerant to mescaline are cross tolerant to LSD aned vice setsa,

Methods

Ezperiments. Two experiments were performed. Esperinent I was a comparison of the effeets and a tletermination ot the cquivalent dosages of LSD, mesealine, and psilocin in 1o subjeets. The data on psilocin will

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Psychopharmacologia 3, 1-14 (1062)

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not be presented iu this paper bnt wil be reportel separately: Experimeat I was a study of eross toleranee ixetween LSD and uésealine in 10 subjects.

Experiment I

Experímental design.. A "single-blind" cross.over design was en. ployed in this experiment (patients tlil not know the drugs they were receiving, but observers did known). Each subjeet reeeived. in ranlomized order at weekly intorvals, two doses of LSD and mesculine. Placebos were not ineluded sinco experieuco (IsaELL. et al., 105a, 1901) has shown that iotmer morphine addiets do not reaet murkedly to placebos. For comparison, placebo dlata from anothor expetintent (IsBELL et al., 1959) are presented.

Subjects. The subjects who volunteered for this exporiment were former opiate addiets who were serving sentonees for violation of Uuitel States nareotic laws. Theie ages varied between 25 to 35 years, all were physieally healthy muales, and none presentedl any evidenee of the nuajor psychoses. Al had psychiatrie diagnoses of eharacter or personality disorders and all had received LSD in previous experineuts.

General conditions. The subjeuts entered a spocial warl devoted to elinieal researeh the night beforo the day on which test drug was administered and remained until the foliowing morning. Observations were performed by speeially trained aides with long experieuce in deteet. ing behavioral changes due to drugs. The patients were toll nothing about the nature of the drug they wevo to receive or the purposes of the experiments.

Drugs and doses. LSD tartrato and mesenline hydlrochloride were administered intramusoularly in doses of 0.75 megkg and 1.5 meg,kg (LSD), and 2.5 mg/kg and 5.0 mg/kg (mescaline). The drug concentrations emploved for LSD antl mescaline were 30 meg/ml and (iș)ung/n respeetively, in distilled water. Prior to administration each doso was diluted to a constant 5 ml volume with sterilo pyrogen-frce physiological salino sohution. The following detailed obscrvations were uuade at hourly intervals after 10 minutes rest in bed, twice beforo. and cight times after administration of drugs: rectal teuuperature, pulso rate. systolie blood pressure, pupillary size, and thresholì for elicitation of tho keejerk. Tho methods used were those previously deseribed bv IaßEut. et al. {1956, 106i). In addition tho subjeets (witl the hcłp of an aile) cómpłeted a special questionnaice at hourly intervals from 7.3n) . to 3.30 p.m. At theso saine times general qotes on behavior were writtert. Clinical grades of the intensity of the renetion were assigned aecoriing to the systom of'Isε.L et al. (1956).

Analysís of data. The changes in rootal tomporature, pulse rati pupillary size, blood pressure and threshokt for elicitatiou of the kitee

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jerk were eaļculated by subtracting the average of the two pre-drug observations from the values obtained at the various hours after the drug. The areas under the time-action curves for each of the above measurements composed of these figures were caleulated by the męthod of W and FL, thus converting all the data on a particular drug, a particular measurement, and. a particular day to one figure termed "degree-hours" (temperature), "rate hours" (pulse rate), ete. "Positive" answers on the questionnaire were scored by counting all ¿ positive responses that were not scored positively before the drugs were given. Means and standard errors of tho means were calenlated aecording to standard statistiéal techniques (EpwarDs). Calleulations of the relative potency of LSD and mescaline were performed on each of these parameters, using a method (Gaddtu) for four-point assays.

In order to obtain time-action curves, changes in temperature, pulse rate, systolic blood pressure. pupillary size. and threshold for the kneejerk were tabulated and averaged for each observation time after the drugs. The number of positive responses on the questionnaire were also averaged at each observation tine. In addition to providing data on the time-action course, these tabulations ideatified the time at which the greatest (peak) respouses occurred. Additional caleulations of re. lative poteney (Gaddtar) were mnade using these peak values.

In order to compare the patterns of subjective response the 57 ques. tions were classified into nine categoriesi, The questionnaires were then scored by counting the number oi patients responding positively to a given question, after which the scores for all the questions constituting the partieular category were sumned.

Experimnent II

Experimenial design. A"cróss-over" design using each patient as his own control was employed in this experiment and is summarized in Table 1. The design was similar to that used in testing eross-tolerance between LSD and psilocybin (IsbεLl, et al., 1961).

Subjects. The same 10 subjects were employed who were used in Experiment I.

General conditions. Subjects were housed in the samo special research ward mentioned in Experiment I. Temperature, respiratory rate, and blood pressure were measured three times daily after the patients had rested quietly in bed during days on which special measurements were

1 The nine categories are shown in Table 5 and are the same that were utsed in comparing LSD and psiloeybin (IsaeLL 195D). As previously explained, a large number of other categories could be devised and many questions conld be classified in varigus eategories. The ciassification thecefore is completely arbitraty. 1

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not being made. All measurements were made by the same aides as in Experiment I.

Drugs and doses. LSD and mescaline were adininisiered intramuscularly at S a.m. (during the control period and on test days) or at 6 a.m. (during the periods of chronic intoxication). No placebos were employed in this study because of the negligible subjective response of our subjects; because placebos have no real value in assessing tolerance and cross tolerance, and beeause the addition of placebo trials would have prolonged the experiment unnecessarily. In the first and second cuntrol periods tho patients received LSD 1.5 meg'kg, and mesealine ã.0 mg'kg in randomized order before chronic administration of the drugs was begun. Detailed observations were made on these test days. Tliese control experiments were condueted at intervals of at least five days in order to prevent development of toļeranco during fhe control period

During the first and second periods of chronie administration, the patients received intramuscularly 0.30 megkg of LSD or 1 mgykg of

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meseaiine on the first day. These doses were inereased by 0.31 meg/kg (LSD) or 1 mg/kg (mescaline) daily until the patients were reeciving 15 meg/kg of LSD or 5.0 mg kg of mescaline ou the fifth day. Theso doves were maintained through the l4th day after beginning chronie intoxication. On the läth dny the patients were "challenged" with the dose of drug they had been receiving (test of "direet" toleranco). On the 16th day they were "challengedl" with the test dose of the alternate drug (test of "eross" tolerance). On both of these days detailed measure-

ments were made.

The patiènts then seceived no merlication for 14 days in order to lose tolerance:

Following this withdrawal period. "second control" measurements were obtained after the patienta: had received in randomized order mesealine 5.0 mg kg, and LSD 1.5 nieg kg, with at least five days intervening between administration of either drug.

The patients then again zeceived the drugs chronically; those patients who had received LSD in the first period of chronie administration were given mescaline according to the schedules deseribed above and rice versa. They were then "challenged" with LSD and mescaline in the same manner as previously described.

Obserrations. Cn test days all observations were periorned in identical fashion to those described in Experinent I.

Analysis of data. The areas under the time-action curves were obtained for each subjeet and each test condition (including first and second controls and all "challenging" tests) in the manner deseribed in Experiment I. In addition, mean peak response values were obtained (as in Experiment I) for each parameter except "clinical gradle," since the latter consisted of only a single figure.

The difference in the various area measurements after l.5 megkg of LSD on the first and secoud controls were evaluated by a t-test for paired obsorvations (Edwarps). Data on the two sets of controls after 5.0 mg/kg of mescaline wero treated similarly. Inerease in blood pressure was significantly greater after LSD. There were no significant differences on other parametera (Table 2). In addition, the differences between the two controls were cvaiuated by a non-paramctric rank order test for paired obsorvations (Wicoxos). Since the significances of the differenees by this latter statistieal technique agreed well with those obtained by the t-test on the time-action (area) figures, oniy the latter are herein presented.

In order to test for equivalence of the doses of LSD and mescaline in Experiment I. the average peak values obtaiued on the two controls with 1.5 meg/kg of LSD were eompared with the avorage values obtuined

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Figures represent the muean differences - the standard errors of the differences betyreen responses to LSD-25 (1.5 megkg) and nescaline (3.0 mg/kg) in the first and-second controis.

\+ Indicates an increased response on the second control.

\_ Indicates a decreased response in the second control.

i Indicates siguificance $( \bar { P } < \bar { 0 } . 0 5 ) .$

on the two controls with 5.0 mg/kg of mescaline (Table 3), using the t-test for paired data. Similar ealeulations were made using the area measurements.

The differences in the response after chronic administration of both LSD and mescaline were evaluated by comparing the responses after

Figures respresent mean differences ± S:E. of differences between mean peak control responses to LSD-25 (1.5 meg/kg) and mesealine (5.0 mg(kg).

\+ Indicates LSD-25 stronger in effect than mesealine.

— Indicates mescaline stronger in effect than LSD-25.

1 Indicates significance $( \mathcal { P } < \hat { \boldsymbol { \ v } } , 0 \hat { \mathbf {  { a } } } ) .$

first and seçond ehronic admini. strations of L\$D and/or mescaline with their respective first and second controls using ths t-test for replicated data (EDRS). Four different comparisons were made: (l) response to LSD after chronie administration of LSD ("direct" tolerance to LSD), (2) response to mescaline after chronic adninistration of LSD ("cross" tolerance to mescaline), (3) response to mescaline after chronic administrationofmescaline "direct" tolerance to mesca. line), and (4) response to LSD after chronic administration of mescaline (“crosss" toierance to LSDì. The sirns of the diffe. rences were so arranged that

a minus (—) sign indicateri a deerease in the neasuremcnts after chronic administration as compared with conttol, and a plus (÷) sign indicated an increase.

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Since mescaline has a longer duration of action than LSD the differences. (except for "elinical grade") were also evaluatcd, using values obtained at the peak of both LSD and mescaline reactions rather than using the areas (integrated time action curves) as described äbove. .In addition, the differences were evaluated by Wcoxox's non-parametric rank order test for paired observations. The significnnce of the differences by these statistieal techniques agreed well with those obtained by the t-test on the time-action (area) figures, so only the differences. obtained by the area method are shown in this paper.

Results

Experimnent I. The objeetive and subjeetive changes induced by LSD and mescaline were very similar. As can be seen in Table 4, both drugs

Figures sre means (9 subjecta an placebo; 10 on LSD and mescaline)  standard errors of areas under time-action eurves ("degree-nours,""beat-hours," ete.). The signs indicate inereases (÷) or decreases (—) in the measurement from predrug controls. urug cv.

Means ± standard errors of number of questions scored positively in the 7/. hours after the drug which were not seored positively before the drug.

Means standard errors of intensity of mental reaction based on a scaleof O4.

caused incrcases over pre-drng measurements in body temperature, pulse rate, systolie blood pressure, and pupilary size, and both decreased the threshold for elicitation of the kneejerk. The table also shows that

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1 Refers to type of question, e.g, "feeling strange"(general): "feet look old" (depersonalization); "am happy" (mood); "things look small" (visual distortion); "is difficult to coneentrate" (thinking), ete.

a Xumber of subjects tirzes number of questions in categor.

Based on responses of 10 different subjects in another experiment.

the changes in the various measures were far greater than those that accurred in a different group of subjects after placebo. The magnitude of these changes was aboutthe same after 0.75 meg kg ofLSD and 2.5mig kg --1 \~

Did not meet eriterion for equivalence of dosage.

of mescaline, crafterl.5meg, kg of LSD and 5.0 mgkg of mesealine. Both drugs induçed anxiety, alterations in mood (generally "euphoric"), diffi. eulty in thinking and concentration. sensory perceptual distortion particularly visual, and both caused true- and pseudo-hallucinations.The subjective symptoms reported after mescaline were very similar to those dlescribed in the literature. Table 5 illustrates the similarity of the patterns of the subjective response aiter LSD and mescaline.

LSD and mescaline differed in time-nction course. In general tho action of mesealine persisted longer than that of LSD with peak effect being reached later and/or being longer sustained (Fig. 1 and 2). These

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eurves show that pupillary dilatation after both mescalino and LSD lasts much longer than do tho subjeetive effeets. They aiso show that the peak subjective effects of mescaline, as measured by the responses on the questionnaire, were less than those after LSD. The subjective effects of mescaline subsided more slowly than did those of LSD.

Caleulations of relative potency are summarized in Table 6. Significant dose-effect siopes were not obtained for pulse rate and threshold for the kneejerk for either area or peak data, so these measures are omitted from the table. Signifieant slopes were obtained on all other measures and, with the exception of area measurenient for pupillary change which did not meet the eriterion for equivalence of effects at the doses used, the regressiou lines for all these measutes met the requírements for equivalence of dosage and paralelisu. These ealeulations show that LSD tartrate is about 2400) to 4900 titnes as porent as mescaline hydrochloride, dependirig on the measurement chosen. On a moleeular basis, LSD is 4500 to 9275 times as potent as mesealine. It should

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be noted that mescaline is more potent in dilating pupils relative to its . potencý in inducing subjective responses than is LSD, 7

Experiment II. Oross tolerance beticeen LSD and mescaline. Controls. The differences in reaponses to the same drug in first and sécond controls after LSD and mescaline are shown in Table 2. The only change that was statistically significant (p<0.05) was an increased elevation of blood pressure after the second control dose of LSD. This could indicate simaple variability of response to LSD on this particular parameter.. The table shows that no significant degree of residual tolerauce was present at the time the second controls were done.

Equiralence of dosage. The differences in the mean peak responses to the two different active drugs (LSD and mescaline) are presented in Tabte.3. It will be noted that although four of the six comparisons indieatethat LSD may have produced a somewhat stronger response than meacaline, the only statistically significant difference letwcen the two drugs is in elevation of blood pressure. The magnitude of the difference ia smal and probably reflects the variability of response -on blood pressure after LSD when administered on separate occasions to the same subjects (see above). Since the majority of differences are positive, there is some indication that. on the averáge, the peak effects of LSD may have been somewhat stronger than those oi mescaline. Similar calculations tsing area measurements instead oi peak values gave identical results with one exeeption. Total pupillary dilatation after mesealine was signifieantly greater than that after LSD. This difference from the results with the peak data reflects the more sustained action of mescaline on the pupil.

Tolerance and cross tolerance. The differences in responses to LSD and mesealine after chronic administration of either drug and their respective first and second controis are shown in Table T. In this table the first column of figures shows the differençe in response to LSD as compared with the corresponding first or second control after chronic administration of LSD, and reflects "dicect" tolerance to LSD. The second column of figures shows the difference in response to mescaline as compared with the appropriate control after chronie administration of LSD, and reflects "cross" tolerance to mescaline. Similarly, the third column of figures presents measures of "direct" tolerance to mescaline, and the fourth coluzun of figures, "cross" tolerance to LSD.

Inspection of Table 7 shows that ail the signs are negative, intiieating an average deercase in response on al measures. In the case of "direct" tolerance to LSD (first column of figares), the diiferenees were statistically significant in six of the seven measures. In the case of "direct" tolerance to mesealine (third colunun of figures), statisticaly significant change oceurred in three measures, and in the case of "cross" toleratco

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to LSD (fourth column of figures), significant degrees of change occurred . in four parameters. The measures which reflected "direet" tolerance and "cross".tolerance most clearly were pupilary diameter, responses on questionnaire, and the elinical grades.

Figures represent the mean differences ± the standard erors of the differences between responses to first control doses of LSD-25 {1.5 mcg:kg) or mezcaline {5.0 mng/kg) and identical "test" and "challenging" doses of these drugs after a first period of chronie intoxication with either drug; and, second control doses of LSD-25 (1.5 mcg/kg) or mesealine (5.0 mg/kg) and identical "test" and "challenging" doses of these drugs after a second period of chronie intoxication with the other drug. er :-isiastion

\+ Indicates increase in response after chronie intoxication.

Indicates a decrease in response after chronic intoxication.

1 Indicates significance (P < 0.05).

1 Indicates significance $( \vec { \mathbb { F } } < \hat { \mathbb { O } } . \hat { \mathbb { V } } \vec { \mathbb { Z } } ) .$ (P < 0.02).

Indicates significance (P < 0.01}.

Diseussion

As expected from the deseriptions in the literature, the reactions induced by LSD and mescaline proved remarkably similar, differing chiefly in rate of onset and duration of aetion. Both drugs caused similar changes in autonomíc funetions which were nearly identical in degree at doses inducing equivalent grades of mental aberration, The subjective symptoms reported sfter the two drugs were very similar in kind and incidence. It is, of course, possible that the similarity in the subjective response was partly caused by the methods of measurement and the experimentai situation. All of our subjects had received LSD on other oecasions and might have expeeted similar symptoms from any drug given in this particular testing situation. In addition, the use of the questionnaire may suggest certain symptomns. However there are cogent

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reasons against the similarity being duc to the experimental situation or to suggestion. The patterns of effeet after inany other drugs (anphetamine, scopolamine, marihuana, ete.) in the same kinl of subjects and under the same conditions differ markedly from the pattern indueed by mescaline and LSD. In adlition, the similarity between the LSD and mescaline reactions is readily apparent in the deseriptions in the litera. ture, even though the subjecta were tested under widely varying couditions with different mèthods, and in subjeets who received only mescaline or LSD. Thus it seems likely that the similarity between the renctions caused by LSD and mescaline is a real phenomenon and not an artifact due to the methods of testing.

The similarity of the effects of LSD aud mesealine suggests that the two drugs aet by common mechanisms or througl some final common pathway. This hypothesis is: strongiy reinforced by the finding (in agreement with BaLEsTrreRr, 1957) that definite cross tolerance dleveloped between both drugs on chronic administration. Direct tolerance to mescaline and cross tolerance to LSD coukd not be demonstrated on as many measures in patients receiving mescáline chronicálly as could direet tolerance to LSD and cross tolerance to mescaline in patients receiving LSD chronically. However a high degree of direct and cross folerance. occurred in both iustances on the most reliable and least variable of the measures (pupillary change, responses on the questionnaire, and clínical grade).

Since persons directly tolerant to LSD are cross tolerant to psilo. eybin (Is, 1961) it seenus likely, although not proved by direct experiments, that persons direetly tolerant to psilocybin would be eross tolerant to mescaline. LSD, mescaline, and psilocybin appear to constitute a definite group of drugs with identical or closely related biological effects, just as morphine, methadone and meperidine constitute a bio. logically related group of analgesic drugs exhibiting high degrees of cross tolerance.

Sinee psiloeybin is an indole and since LSD can be regarded as an indolé; one might bypothesize that the sinilarities in biological effect and the development of tolerance and cross tolerance are relaterl to similarities in chemical configuration. Mescaline is, however, not an indole, and although it has been postulated that mesealine is converted to an indole in the body, no direct evidence of sueh a biotransformation exists at present. In faet, investigators who have studied the biotrans. formation of mesealine have reported that mescaline is excreeted largely unchanged (Woons et al.), or partly unehanged and partly as 3.4,3-trimethoxphenylacetic aeid (Srcor). For the nmoment. it seems best to attribute zhe sinilarities of action of LSD, mescaline and psilocybin to some common biologieal meehanism rather than to similarities in chemical structure.

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Summary

. 1. The reactions caused by intramuscular administration of 0.7ümeg kg and 1.5 meg/kg of LSD-25 have been compared in the same 19 subjeets with those induced by 2.5 mg/kg and 5.0 mgkg of mescaline

2. Both LSD and mescaline caused dilatation of the pupils, incrense in body temperature, elevation of pulse rato and increase in systolic blood pressure. Both drugs decreased the threshokl for elicitation of the kneejerk.

3. After both drugs, sinilar abnornial mental states eharacterized by anxiety, difficulty in thinking, alteration in muood (generally euphoric), altered sensory perception (particularly visual), elenientary and true visual hallucinations and alterations of body image were reported by the subjects.

4. The effects of mescaline appeared more slowly and persisted somewhat longèr than did the effects of LSD.

5. LSD tartrate is 2400—190) times as potent as mescaline hydrochloride. On a molecular basis, LSD is 4500 to 9275 times as potent as mescaline.

§. Patients receiving LSD daily developed direct toierance to LSD; such patients were also eross tolerant to mescaline. Likewise patients receiving mescaline daily became tolerant to mescaline and cross tolerant to LSD.

7. It was inferred that LSD, psilocybia and mescaline probably share common mechanisms of action or some common final pathway.

Aeknewledgmnents. We are indebted to Drs. R. BircHEs and C. Hsxzz of Sandoz Pharmaceuticals, Hanover, N.J., for supplies of diethylamide of lysergic acid tartrate (LSD-25), and to Dr. L. A. Pre, Hoifmann-La Roche, Ine., Nutley Park. N.J., for aupplies of mescaline hydroehloride.

References

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Haaris IsazLL, M.D., Direetor N.I.M.H. Addiction Researeh Center U.S. Publie Health Service Hospital, Lexington, Kentucky, U.S.A.