Laszlo Gyermek

It fell upon me, almost accidentally, that I developed a research interest in this important as well as notorious biogenic substance, an alkaloid of the coca plants, grown and cultivated widely on the slopes of the Andes mountains in South America. Had I not become engaged, in my early career as a neuropharmacologist, with atropine, another well-known bioactive alkaloid, even more widely occurring in nature, I would not have been involved with cocaine. (Fortunately I did not belong to those in our society who use it as a recreational, often very addictive, drug.) My attention to cocaine developed first when I recognized its chemical, but not pharmacological, similarity to atropine, an agent I worked with intensively as a young researcher.

Shortly before having obtained my M.D. degree, in 1949, I became a pupil of Bela Issekutz, head of the Pharmacology Department at the University of Budapest. He was a notable drug researcher in a country that had a historic reputation in pharmaceutical sciences: pharmacy, pharmacognosy, pharmacology, and organic chemisry. Issekutz, had already done pioneering work in the early 20^th century with some of the first synthetic derivatives of atropine, which captured my interest; and thus I gained the necessary chemical and pharmacological know-how about  atropine, other tropane alkaloids, and their derivatives. Cocaine was one of those.  I was primarily working with the peripheral “anticholinergic” actions of tropane, a bicicyclic amine [8-methyl aza bicyclbicylco (3.2.1) octane], an essential building block of atropine, and its synthetic derivatives. Together with Karoly Nador, an organic chemist and  associate  of Issekutz, we made new observations about the “anticholinergic“ structure - activity pharmacology of  tropane  derivatives(1,2), which became  part of the thesis work for my Degree in Pharmacology .

Because cocaine did not have a significant action on the “parasympathetic division” of the autonomic nervous system, it was not of interest to me at first. The other reason for bypassing cocaine initially was because it was difficult to convert this molecule from a “tertiary amine” form   to the more highly protonated “onium cationic” species (at least at that time). On the other hand, with a variety of halogenated quaternizing groups, we obtained and studied a wide array of new tropane and atropine derivatives (3, 4), some of them (see e.g. Gastropine / Gastripon) with therapeutic interest and success. 

For me cocaine emerged as a valuable “pharmacologic” probe only some years later, when I already have settled in the United States. Because of this “relocation”, I also had to change my professional course.  First at the University of Illinois,  Chicago I was asked to work primarily  with the structure-activity  relationship-pharmacology of  the derivatives of another  alkaloid: the mushroom poison, muscarine; and subsequently, at the Geigy Research Laboratories in New York, I  became engaged with  the, at that time  new,   “tricyclic” antidepressants.  In this course of transition, my previous experience with the classical, small molecular, neurotransmitter, and modulator molecules, e.g. adrenaline, noradrenaline, acetylcholine, histamine, and serotonin, became a handy asset. At Geigy, we studied the interactions of the first synthetic antidepressant agents with noradrenaline, which was originally believed to be the most important biogenic amine involved in the mechanism of action of tricyclic antidepressants (and cocaine). Here again my chemical pharmacology background helped me to be involved in developing an alternative hypothesis regarding the possible action mechanism of the tricyclic antidepressants. I used serotonin, at Geigy, also for a “chemical pharmacology reason”. Even before the emergence of imipramine, the first tricyclic antidepressant, serendipitously “stumbled upon” by the Geigy researchers in Switzerland while searching for new antihistamines, I had already conducted experiments in the mid-1950s in Hungary in isolated smooth muscle organ preparations with some phenothiazines, including chlorpromazine, (known for their psychosedative, or ”neuroleptic“ actions). I compared their  antihistamine and antiserotonin potencies and found  first, in 1955, that chlorpromazine was a much more potent  serotonin blocking agent than it was  an “antihistamine”; and that the rank  order of  the antiserotonin potency of four  phenothiazines  matched their  neuroleptic  potencies (5,6). I reasoned that the structure of the phenothiazines, being properly substituted “propylene diamines”, (mimicking  a “ serotonin fragment”) may show a preferential affinity to smooth muscle serotonin receptors as compared to most antihistamines, which  were substituted ethylene diamines (mimicking a “histamine” fragment). In 1960, shortly after I joined Geigy Research in New York, realizing that the first “tricyclics” were also substituted propylene diamines, we evaluated the first  prototypical “antidepressant“, imipramine  using   the ”serotonin – probe”.  The results in cat blood pressure and “nictitating membrane” preparations indicated not only that imipramine was a strong enhancer of the serotonin-induced effects, but in this respect it was acting preferentially toward serotonin as compared with norepinephrine (7,8). It was almost mandatory at that point to include in these experiments cocaine, long known as a catecholamine–potentiating agent in animal experiments. (At that time the mono-amine reuptake inhibitory action of both the tricyclic antidepressants and cocaine had not yet been elucidated). The results showed that in contrast to imipamine and some other ”tricyclics”, which usually showed relatively selective potentiation toward serotonin, with cocaine the situation was just the opposite: It was a relatively selective potentiator of the catecholamine-induced (“peripheral’) effects.

What turned my interest toward cocaine was the landmark discovery of Gaddum, in 1954, who first proved that serotonin possessed two different types of stimulant actions on isolated intestinal  preparations (9). He utilized few, I believe, randomly chosen and well known pharmacologic probes. Of these, morphine and cocaine were found to be effective antagonists of the stimulant action of serotonin on its receptors in the neural plexuses of intestine. Dibenamine (an alpha sympathetic blocking agent) inhibited another type of action of serotonin, related to the so called “muscular” receptors.  By then I was also involved with serotonin, and did research with its early antagonists (10). We could demonstrate first, in 1960 that cocaine blocked the effects of serotonin in the sympathetic ganglia of the cat more selectively then did morphine.  My early research with serotonin was recognized in 1962, when I presented a review lecture on serotonin antagonists at the plenary session of the International Congress of Physiological Sciences (11). In this presentation, I emphasized the relative selectivity of cocaine as a “neurotropic” serotonin antagonist. Based on these early publications, it became apparent that tropane derivatives, similar to cocaine, should capture interest in developing new serotonin antagonists. I could not embark on such project because from 1962, I became employed by the Syntex Corporation in California, where the emphasis was on steroid pharmacology research… Thus, it was not  surprising that soon thereafter a new line of  “cocaine”- type antiserotonin agents appeared on the horizon from Merrell Laboratories in France, where the research, directed by Fozard utilizing tropacocaine first,  led to the tropinester:  3,5 dichlorbenzolyl tropine (MDL 2222),  Bemesetron,  the first “neural serotonin receptor” (later identified as 5-HT3 receptor) blocking agent (12). It was introduced clinically as  a new type of  antiemetic. An obvious choice for molecular design, aiming at further novel antiemetic, antiserotonin drugs was to synthesize  the 3-indole acetic acid  ester of tropine  which was studied and introduced as  “Tropisetron”  by Sandoz (cf. 12,13). The importance of the  alpha-branching tropane-–like  bicyclic ring system, as an important functional group of  potent 5-HT₃ receptor blocking  agents, became  underlined by the extremely high potency of  the subsequently developed antiemetic  Granistron, a cyclic amino acid ester amide of Granatanol [ 9 aza bicyclo (3.3.1 nonane 3 (endo) ol ] (12,13).

In the last few decades, intensive research has started on developing new derivatives of cocaine. This was prompted by discovery that the pharmacologic action-mechanism of cocaine in the CNS involved the catecholamine receptors (mainly dopamine) (14,15,16).  Although more than a century ago, a few derivatives of cocaine had been synthesized in Europe and evaluated for local anesthetic action (cf. Barlow 1964) (17); according to my knowledge, the first seminal paper that reported (taking into account the emerging “catecholamine action mechanism” theory) the synthesis and biological evaluation of  28 new derivatives of  cocaine  which came from the Sterling Winthrop Research Institute in 1973.  In this study, the main change in the cocaine molecule was replacement of the benzoyl ester group with a sterically more rigid phenyl group, creating the first synthetic 2-beta carbo-alloxy - 3- phenyl tropanes (18).  The most significant three derivatives of this study were:  a. 2 -beta carbomethoxy, 3-beta phenyl (8 methyl azabicyclo [3.2.1] octane, b. its  nor–tropane analog, and c. its  para-fluoro substituted derivative on the phenyl group  (WIN 35-428). These three cocaine-based compounds had a 15-20 times higher potency than cocaine, in animal tests. Further, their i.v. toxicity was less than that of cocaine; and in  tissue (NE  uptake) binding tests, they also  surpassed cocaine (18).  WIN 36,428 later was studied in more detail; and, for example, it also turned out to be a quite selective 5-HT reuptake inhibitor in brain membrane preparations (19). Not surprisingly, it became a cocaine-like recreational psychostimulant “designer drug”.

The highly potent Sterling-Winthrop cocaine derivatives, and I also believe, a research proposal (1989) and NIDA Grant application (1991) by us (to be discussed later), triggered the search for more new classes of synthetic, cocaine-like molecules. The structural alterations were manifold, and in the last three decades several comprehensive studies covered their  SAR pharmacology aspects, particularly at the “Research Triangle Institute” (RTI) in North Carolina.  Of primary interest was changing, or eliminating, one or more of the obvious,  important  “functional groups“ of cocaine: 1. the 2 carbomethoxy – radical, 2.  the tropane 3–ol ester  group, and 3. the N  atom of the tropane ring. Particularly large number of new substituted 3- phenyltropanes have been produced which were explored particularly as DA, NE, and 5HT  transport-inhibiting agents.  Several hundred such phenyltropane derivatives of cocaine were included in a significant and comprehensive review of Singh (20).  Recently, more radical  chemical changes were initiated  on  the tropane ring by  synthesizing 8 oxa  and 8 thia azabicyclo (3.2.1) octane derivatives (21,22)  and  a. extending the tropane ring  to  8 aza bicyclo (3.3.1) nonane,  b. reducing to  7 aza bicyclo ( 2.2.1) heptane,  c. replacing the  alpha- branching ring systems with, for example, a piperidine ring ( cf. 20). (It should be noted that all these rings contained the functional radicals, characteristic for cocaine.) As mentioned, some of these new agents proved to be highly selective noradrenaline, dopamine, and / or serotonin transport inhibitors (20, 23 ).

Recently, the cocaine research group of RTI discovered that cocaine and some of its analogs are potent labeling ligands for the CNS nicotinic ACh receptors (24, 25), where their subunit compositions are mainly of the “alpha-4, beta-2” type. Such affinity  for  cocaine could not be detected in earlier pharmacological studies on peripheral nervous preparations  (e.g., autonomic ganglia, where the  nACh receptors  are  predominantly of the “alpha-3, beta-4” subtype and at the neuromuscular  junctions where the nAch  receptors belong to the “alpha-2, beta, delta, gamma (or epsilon)“ subtypes. These  latter receptor types are known to bind a great variety of azabicyclo octanes (e.g. tropanes), nonanes, (e.g., granatanes), and  azabicyclo heptanes, exemplified by very potent autonomic ganglion stimulating and blocking agents such as Epibatidine, a [2- beta ( 2  chloro–5 pyridinyl ) 7 aza-bicyclo (2.2.1) heptane]; other tropane and tropine ester  derivatives (such as N-417 and  N-399 )  (26); a cocaine-derived  nicotinic receptors – stimulant and spinal analgesic agent, MT855;  an 8 azabicylco (3.2.1) octane analog of epibatidine] (27);  and many neuromuscular blocking agents belonging to the dimer tropane, tropine  and granatanol - types (28, 29).

These structural examples and considerations underline the importance in drug design of “alpha branching cyclic aminoalkanes”, a broad chemical class  represented  by many  important pharmacologic probes and clinically useful drugs, e.g., atropine, scopolamine, cocaine, tropacocaine , epibatidine,  anatoxine, and their newer derivatives.

From 1966, I have re-trained myself  in anesthesiology, and  for  more than two decades I  was involved  mainly  with clinical  practice and research  in anesthesiology.  However, in the late 1980s, I re-kindled my interest in cocaine-related research. As a faculty member of the Department of  Anesthesiology  at  UCLA  (Harbor UCLA Campus), in an exploratory letter  to the NIDA  in August 1989,  I wrote : “I am aware of  the program of  Research Grants offered by the NIDA for research which addresses the broad scope of  drug addiction. Gaining fundamental knowledge into the mechanisms of action of human drug addiction and exploring its practical medicinal aspects such as prevention and treatment are the primary objectives…. In the meantime, drug abuse in the U.S is steadily growing, and the amount confiscated (cocaine) by the law enforcement agencies becomes staggering …. a well planned project, which would explore the medicinal research use of confiscated cocaine would have large commercial, social and public health significance. ..The proponent is in an excellent position for planning, and of executing the contemplated research program …..He has experience in neuropharmacology with many drugs, including cocaine… and has particular expertise with agents affecting the cholinergic and serotonin (related) neural mechanisms …and (is) thoroughly familiar with the chemistry of cocaine or related natural (tropane) alkaloids”.

Following this preliminary communication, I decided to organize a multi-institutional “consortium” research program aiming at the design, synthesis, and pharmacological evaluation of new therapeutic agents for which the starting  material would have been  confiscated cocaine. Three well-known  researchers in the cocaine field  and myself would have been the principal investigators of the collaborative research project, for which a proposal  was submitted to the NIDA  in 1991 by  Gabor Fodor, Professor Emeritus of Chemistry at West Virginia University, a specialist of cocaine and tropane chemistry;  Abel Lajtha,  Director of Neurobiology Research at the N.Y. State Neuropsychiatric Research Institute in New York City,  a recognized neurochemist, active in cocaine related research;  the experimental  psychopharmaclogist,  Larry Stein,  Professor and Chair of the Department of Pharmacology at the University of California  Irvine; and myself as the proponent, and at that time, Professor of Anesthesiology at the  University of California at Los Angeles/Harbor UCLA Campus.

The goal of the research plan was to design and produce new drugs derived from cocaine and applicable for: 1. the  symptomatic treatment of cocaine abuse  2. other possible therapeutic applications, e.g., as local anesthetics, antiarrhythmic agents, antidepressants, analgesics, muscle relaxants, and antiemetics.  Based on the chemical structure of cocaine, with emphasis on its pharmacologically  important groups, and with particular emphasis on their  steric orientation and molecular- energetic factors, we planned to focus on  structural modifications on: a.  the  C2 carbomethoxy gourp, b. the  C3 benzoylester group, (either by eliminating some groups or by using suitable  substituents on these groups), and c. the N atom (by introducing N – alkyl and aralkyl substitutions on the secondary N atom of nor-cocaine, or if possible,  producing  mono- and bis- quaternary ammonium derivatives of cocaine).

Examples of each of these planned categories were: 1. 2-amino-and 2-amidine-3 tropanols  (from ecgonine,  benzoylecgonine, and pseudo benzoyl ecgonine through different synthetic routes), 2. new types of esters derived from ecgonine methylester, replacing the benzoyl ester  group  of cocaine (e.g., tropic acid  ester, indolylmethylester, and trifluoromethyl  ester), 3. long chain N-alkyl  and aralkyl  derivatives of nor-cocaine  by using alkyl halides or alkyl tosylate, and in case of the quaternization of the of cocaine, utilizing psueodococaine and/or the “reverse quaternization” methodology.

Among the many exciting molecular design possibilities worth of mentioning were: to prepare a  cocaine-dopamine hybrid molecule: N- 3,4,dihydroxphenylethyl–nor cocaine (suggested by G.Fodor), derivatives of the cocaine analogue of  N-phenylbenzy (p-aminobenzoyl) tropinium (N-417),  an extremely potent nicotinic receptor stimulant (Gyermek and Nador, 1954) (cf, 26),  and a scopolamine-cocaine hybrid (based on the work with scopolamine on the blood–brain barrier penetration by Larry Stein (Personal communication).

Even that our application has not been awarded grant support, I assume it must have had some impact on cocaine related research in the US. It was interesting, for example, to note that  from the time of  my first disclosure proposing to develop new cocaine derivatives, in 1989, to our formal application to the NIDA in 1991, there has been an upsurge in cocaine-related  research, exemplified by  the  emergence of the previously known (and  almost  forgotten) cocaine derivative WIN-35428 (18). This compound was reevaluated in 1991 (30), along with the synthesis of nor-cocaine, a few of its N- substituted derivatives, and changing the Chloro atom to Iodine on the benzene ring of WIN- 35-428, resulting in the compound RTI- 55 (31, 32), which was investigated as an “in vivo“ radio ligand-labeling agent, with possible therapeutic potential.  With this surging  interest in the  1990s, a large number of publications appeared from several prominent investigators, who suddenly immersed themselves in “cocaine research”,  developing many new cocaine analogs, which underwent the “run of the mill’’ in vitro  DA, 5-HT and NE  uptake tests  to satisfy the usual initial goal in drug research for “ high potency and selectivity”. By 2000, the comprehensive Synthesis and Structure-Activity  Review  on Cocaine derivatives by Singh (20) has  listed over a thousand  new cocaine-analogs described in  hundreds of publications; and the review of Carroll et al (33) summarized the voluminous preclinical  research, which explored the possible clinical  applications of the new  cocaine  derivatives. I feel that without the “disclosures of our planned cocaine research program  between 1989 and 1991, including some  planning and  technical details, this research field would not have  developed as much as it did.

Beyond the possible obscure “conflicts of interest, priority and bias”  issues, a practical  problem might have also affected the fate of our research proposal: The tight control of cocaine availability in the US, even for scientific purposes. For example, once,  during the preparation of our research application, I had the opportunity to talk to an officer of  the  FBI, who was responsible for the elimination of the largest yet seized  cocaine-lot in the Harbor of Los Angeles that amounted to not less than ten tons!  On my inquiry as to whether it would be possible to obtain from the Agency some quantities from the confiscated lots for research purposes, he could not give any reasonable answer. It was suggested that I turn to the Agency’s Laboratory of Analytical Chemistry in San Diego. They could not be of help either…. These government officials seemingly could not envision any solution for problems falling outside of their rigidly controlled, bureaucratic protocols.

A couple of years after the submission of our proposal, a publication from the University of New Orleans caught my attention. The authors synthesized new cocaine derivatives from cocaine samples (obtained from the NIH!) as part of their research program. I established contact with the senior investigator, Mark Trudell, and we discussed the synthesis of tropane analogs of Epibatidine from his cocaine supplies. He became interested and synthesized  a few  such cocaine -derived Epibatidine analogs, which we could investigate first in, in vitro radio-ligand binding experiments  for affinity  to nicotinic ACh receptors; and later, we found that some of the “tropane” analogs of Epibatidine also displayed significant ”nicotinic type“  spinal analgesic activity (27).  As the affinity of Epibatidine to the nicotinic neuromuscular receptors in the  “Torpedo”  electric organ  was  enormous,  with Trudell we obtained the “cocaine derived”   N, N’ 1-10 decamethylene bis  analog of 6-7 dehydro 2 (exo 3- chlorpyridinyl)  N- Me  azabicyclo (3.2.1) octane  ( SZ- 271). In essence, it was a tropane/epibatidine hybrid dimer. Indeed, this compound displayed significant neuromuscular blocking property (35), indicating that such structures could be used as lead compounds for developing  new  myorelaxants. Another series of new, ultra-short acting neuromuscular relaxants also originated from my “self funded”   collaborative research with Trudell, who synthesized tropane 2-ol, from which we prepared few of its dicarboxylic acid esters and their bisquaternary derivatives, and studied them for neuromuscular blocking action. Of these only a few, e.g., the  Me and  the Phenyl prop- (2 ene) -yl  quaterneries  of the  adipic acid - and  pimelic acid esters of  tropane 2-ol have been reported (36).

In the last few years, because of my advanced age, I could not do any more experimental work with cocaine and with its derivatives.  Still full of “ideas”, but without support and access to adequate  laboratory facilities, I started to feel like a retired or dismissed  musical  conductor, who has lost his  orchestra.  It is worth mentioning that even in my earlier, busiest years in research I could not come even close to the equivalent of a “big band leader”.  In the US, at different Institutions I could work only with few, less than nine  “players”. Of course, the size of the supportive personnel is not always the key for success in biomedical research. In my case, the  close to three hundred scientific publications,  (most with a “single or first authorship”); a marketed new  gastrointestinal drug (Gastripon) and over twenty new  drug discovery-related Hungarian and US Patents, considering over twenty years spent in Anesthesiology, speak for themselves. Controversially, of the well over 40 Research Grant Applications I submitted in the USA, only very few, received acceptance and support.

I felt that in this review I will bring up this anomaly, because many of us in “US Science” fell and still fall into an “under supported” or even “forgotten” professional category. Once I had a discussion with Julius Axelrod, the late, distinguished Nobel Laureate Neuropharmacologist  of the NIH, few years before he obtained the “Prize”. I was amazed to hear that he was working merely with four associates, and had just two laboratory rooms! I have not met him any more after his award, but I doubt that beyond the almost “obligatory” vocal  accolades and short-lived  “Press coverage“ he was not  more “tangibly”  supported, even afterwards.

Looking back now, as an observer only, to the last two decades of cocaine - pharmacology research, which has shifted almost entirely towards molecular “in vitro” and even “in silico”  approaches, it seems that we ended up with a giant  “Library” of cocaine derivatives. Of these derivatives, none has made it to the market as  a therapeutic  breakthrough for the “cure /amelioration”  of neuropsychiatric diseases. If there is any explanation for this,  I speculate that: 1. perhaps cocaine was not the  best  “scaffold” on which a “giant monument” of modern-  and  therapeutically oriented neuropsychopharmacology could have been built; 2. we still have a  tremendous gap in appropriate knowledge, that  persist between  the  “results”  obtained by model systems, like computerized molecular (and sub-molecular) modeling on one side and studying  “deranged  vital  functions” of a mentally ill human being, on the other …  Almost completely eliminating experimentation on animals, particularly on those with a relatively advanced CNS, that  could diminish such gap, is a regretful fact, which  most  of us  should understand; or be educated to  understand. And there is of course the ultimate question: Are we entitled to interfere with Nature, when after all our life span is so limited and hardly amenable to be changed significantly?  We should consider the immense expenditures, that unfortunately, many of us do not, or even worse do not want to understand  within and beyond “Health  Care“; and thus  undermine our present  life  prospects and particularly those  of the future generations.

Now, going back again to biomedical science: Of course the “cocaine scientist” is not much unlike other researchers whose professional life nowadays primarily involves writing Grant- and Patent applications, to establish “support” and  protect their “rights”.  Further, they attend/lead conferences and publish scientific papers full of optimistic forecasts and promises, thereby establishing and maintaining  their reputation, along with a “PR” (public relations) image.  With such  “primary’’ obligations,  they usually leave the “ run of the mill”  laboratory research work  to  the  junior assistants,  e.g. students, “post doc. fellows”, etc. resulting in “collaborative research papers” with immense lists of authorships….  In this respect, the modern biological scientist often is not better, but even worse than,  for example, a practicing physician, who  albeit works  for a handsome fee,  harvesting the benefit of a long and demanding educational process, contributes alone, directly and every day  to the welfare of  a suffering fellow human…

I admit that what I have written here sometimes represented more a theme, such as “Ethics in Science”, than a discussion of an isolated case, e.g. “Relation of a scientist to a drug”, as introduced in the title.  But, since the “script” is the result of an experience, longer than half a century, in “Science”, I hope that, in the format presented, will be of benefit to some….

So much about my reminiscences about cocaine.

REFERENCES

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2.      Gyermek L, Nador K. Studies on cholinergic blocking substances II. Correlationsof  the  antimuscarine, antinicotine and curare-like effects of mono and bisquaternary tropeines.  Acta Physiol Acad Sci Hung 1952; 3:283-93. 

3.      Gyermek L, Nador K.  The pharmacology of tropane compounds in relation to their steric structure.  J Pharm Pharmacol 1957; 9: 209-29.

4.       Gyermek L, Nador K. Pharmacology of (p-biphenylmethyl-dl-tropyl-tropiniumbromide).  Arch Int Pharmacodyn 1957; 113: 1-14

5.      .Gyermek L.  Chlorpromazine, a serotonin antagonist ?  Letter.  Lancet; 1955, II: 724.

6.      Gyermek L, Lazar GT, Csak Zs. The antiserotonin action of chlorpromazine and some other phenothiazine derivatives.  Arch Int Pharmacodyn; 1956 ; 107: 62-74.

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11.   Gyermek L. Antagonists of 5-hydroxytryptamine. Proc 22^nd Internat Physiol Cong Leiden, 1962. Exerpta Med Intern Cong Series 1962; 47: 29-36.

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18.   Clarke RL, Daum  SJ,  Gambino  AJ, et al . Compounds affecting the central nervous  system. 4.  3 Beta-phenyltropane-2-carboxylic esters and analogs. J Med Chem  1973; 16: 1260–7.

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21.  Isomura S, HoffmanTZ, Wirsching  P, et al . Synthesis, properties, and reactivity of cocaine benzoylthio ester possessing the cocaine absolute configuration. J Am Chem Soc  2002 ;124: : 3661–8.

22.  Meltzer PC, Huu DPP, Madras K. Synthesis of 8- azabicyclo [3,2,1] oct-2-enes and theirbinding affinity for the  dopamine and serotonin receptors. Bioorg  Med Chem  Lett 2004; 14:  6007-10.

23.  Blough BE, Abraham P,  Lewin AH,  et al.  Synthesis and transporter binding properties of 3β-(4-Alkyl-4-alkenyl and 4 - alkynylphenyl) nortropane-2β-carboxylic acid methyl esters: Serotonin transporter selective analogs.  J  Med Chem 1996; 39: 4027-35.

24.   Damaj  MI , Slemmer JE Carroll FI, Martin  BR. Pharmacological characterization of nicotine’s interaction with cocaine and cocaine analogs J Pharmacol Exp Ther 1999; 289: 1229-36.

25.  Carroll FI, Blough BE, Mascarella SW, et al. Nicotinic acetylcholine receptor efficacy and pharmacological properties of 3-(substituted phenyl)-2beta-substituted tropanes. J Med Chem  2010; 53: 8345-53.

26.  Gyermek L.  Ganglionic stimulant and depressant agents, In: Burger A (Ed).Chemical constitution and pharmacodynamic action. Vol I, Chapter 4. New York: M. Dekker Publ; 1966, pp. 149-326.

27.  Nishiyama T,  Gyermek L,  Trudell M,. et al.  Spinally mediated analgesia  and receptor binding affinity of epibatidine analogs. Eur J Pharmacol 2003;  470: 27-31

28.  .Gyermek  L,  Lee C,  Cho YM, .et al. Quaternary derivatives of granatanol diesters: Potent, ultrashort acting non-depolarizing neuromuscular relaxants.  Life Sci  2006; 79: 559-69.

29.  Gyermek L. Structure-activity relationships among derivatives of dicarboxylic  acid  esters of tropine. Pharmacol  Therap  2002; 96: 1-21.

30.  Abraham P, Pitner JB , Lewin  AH, et al. N-modified analogs of cocaine: synthesis    and inhibition of binding to the cocaine receptor.  J Med Chem 1992; 35: 141–4.

31.  Boja JW, McNeill RM, Lewin AH, et al. Selective dopamine transporter inhibition by cocaine analogs. Neuroreport 1992; 11: 984-6.

32.  Scheffel U, Dannals RF, Cline, EJ, et al. [123/125] RTI-55, an in vivo label for the serotonin transporter. Synapse 1992; 11: 134-9.

33.  Carroll FI, Howell LL, Kuhar MJ. Pharmacotherapies for treatment of cocaine abuse:     Preclinical aspects,  J Med  Chem 1999; 42: 2721–36.

34.  Ji A, Trudell M, Lin R, et al. Epibatidine derivatives.  Abstract #1511, 12^th World Congress  of Anesthesiologists.  June 4-9, 2000, Montreal. Events International Inc.

35.  Gyermek L, Ji A, Nguyen N, et al. An epibatidine-like bisquaternary agent with strong affinity and action on nicotinic receptors.  IARS 75^th Congress, Ft Lauderdale, FL. March 2001.  Anesth Analg  2001;  92: S-198.

36.  Gyermek  L , Lee C, Cho YM, et al.  A  rat study of correlating neuromuscular   blocking  characteristics with stereochemical features. Abstract #1214. 12^th  World Congress of Anesthesiologists.June 4-9 , 2000, Montreal. Events International  Inc.

Laszlo Gyermek

February 13, 2014