Effects Of LSD Essay, Research Paper

Table of Contents Introduction Table 1:Effects of LSD A Brief Foray Into Philosophy and the Cognitive Sciences The Suspects Figure 1: Structure of LSD Overview of

Synaptic Transmission Theory: LSD Pre-synaptically Inhibits 5-HT Neurons Theory: LSD Post-synaptically Antagonizes 5-HT2 Receptors Figure 2: LSD Binding at

5-HT2 Receptor Theory: LSD Post-synaptically Partially Agonizes 5-HT2 Receptors Theory: LSD Post-synaptically Agonizes 5-HT1 Receptors Conclusion References

Introduction The psychedelic effects of d-Lysergic Acid Diethylamide-25 (LSD) were discovered by Dr. Albert Hoffman by accident in 1938. In the 1950s and 1960s,

LSD was used by psychiatrists for analytic psychotherapy. It was thought that the administration of LSD could aid the patient in releasing repressed material. It was also

suggested that psychiatrists themselves might develop more insight into the pathology of a diseased mind through self experimentation. 1,2 During the late 60s, LSD

became popular as a recreational drug. While it has been suggested that recreational use of the drug has dropped, a recent report on CNN claimed that 4.4% of 8th

graders have tried it. LSD is considered to be one of, if not the, most potent hallucinogenic drug known. Small doses of LSD (1/2 – 2 ug/kg body weight) result in a

number of system wide effects that could be classified into somatic, psychological, cognitive, and perceptual categories. These effects can last between 5 and 14 hours.

Table 1: Effects of LSD 1, 2, 3 Somatic Psychological Cognitive Perceptual mydriasis hallucinations disturbed thought processes increased stimulus from environment

hyperglycemia depersonalization difficulty expressing thoughts changes in shape/color hyperthermia reliving of repressed memories impairment of reasoning synaesthesia

(running together of sensory modalities) piloerection mood swings (related to set and setting) impairment of memory – esp. integration of short -> long term disturbed

perception of time vomiting euphoria lachrymation megalomania hypotension schizophrenic-like state respiratory effects are stimulated at low doses and depressed at

higher doses reduced “defenses”, subject to “power of suggestion” brachycardia The study of hallucinogens such as LSD is fundamental to the neurosciences. Science

thrives on mystery and contradiction; indeed without these it stagnates. The pronounced effects that hallucinogens have throughout the nervous system have served as

potent demonstrations of difficult to explain behavior. The attempts to unravel the mechanisms of hallucinogens are closely tied to basic research in the physiology of

neuroreceptors, neurotransmitters, neural structures, and their relation to behavior. This paper will first examine the relationship between neural activity and behavior. It

will then discuss some of the neural populations and neurotransmitters that are believed to by effected by LSD. The paper will conclude with a more detailed discussion

of possible ways that LSD can effect the neurotransmitter receptors which are probably ultimately responsible for its LSD. A Brief Foray Into Philosophy and the

Cognitive Sciences Modern physics is divided by two descriptions of the universe: the theory of relativity and quantum mechanics. Many physicists have faith that at some

point a “Grand Unified Theory” will be developed which will provide a unified description of the universe from subatomic particles to the movement of the planets. Like in

physics, the cognitive sciences can describe the brain at different levels of abstraction. For example, neurobiologists study brain function at the level of neurons while

psychologists look for the laws describing behavior and cognitive mechanisms. Also like in physics, many in these fields believe that it is possible that one day we will be

able to understand complicated behaviors in terms of neuronal mechanisms. Others believe that this unification isn’t possible even in theory because there is some

metaphysical quality to consciousness that transcends neural firing patterns. Even if consciousness can’t be described by a “Grand Unified Theory” of the cognitive

sciences, it is apparent that many of our cognitive mechanisms and behaviors can. While research on the level of neurons and psychological mechanisms is fairly well

developed, the area in between these is rather murky. Some progress has been made however. Cognitive scientists have been able to associate mechanisms with areas of

the brain and have also been able to describe the effects on these systems by various neurotransmitters. For example, disruption of hippocampal activity has been found

to result in a deficiency in consolidating short term to long term memory. Cognitive disorders such as Parkinson’s disease can be traced to problems in dopaminergic

pathways. Serotonin has been implicated in the etiology of various CNS disorders including depression, obsessive-compulsive behavior, schizophrenia, and nausea. It is

also known to effect the cardiovascular and thermoregulatory systems as well as cognitive abilities such as learning and memory. The lack of knowledge in the middle

ground between neurobiology and psychology makes a description of the mechanisms of hallucinogens necessarily coarse. The following section will explore the possible

mechanisms of LSD in a holistic yet coarse manner. Ensuing sections will concentrate on the more developed studies of the mechanisms on a neuronal level. The Suspects

Researchers have attempted to identify the mechanism of LSD through three different approaches: comparing the effects of LSD with the behavioral interactions already

identified with neuotransmitters, chemically determining which neurotransmitters and receptors LSD interacts with, and identifying regions of the brain that could be

responsible for the wide variety of effects listed in Table 1. Initial research found that LSD structurally resembled serotonin (5-HT). As described in the previous section,

5-HT is implicated in the regulation of many systems known to be effected by LSD. This evidence indicates that many of the effects of LSD are through serotonin

mediated pathways. Subsequent research revealed that LSD not only has affinities for 5-HT receptors but also for receptors of histamine, ACh, dopamine, and the

catecholines: epinephrine and norepinephrine.3 Only a relative handful of neurons (numbering in the 1000s) are serotonergic (i.e. release 5-HT). Most of these neurons

are clustered in the brainstem. Some parts of the brainstem have the interesting property of containing relatively few neurons that function as the predominant provider of

a particular neurotransmitter to most of the brain. For example, while there are only a few thousand serotonergic cells in the Raphe Nuclei, they make up the majority of

serotonergic cells in the brain. Their axons innervate almost all areas of the brain. The possibility for small neuron populations to have such systemic effects makes the

brain stem a likely site for hallucinogenic mechanisms. Two areas of the brainstem that are thought to be involved in LSD’s pathway are the Locus Coeruleus (LC) and

the Raphe Nuclei. The LC is a small cluster of norepinephrine containing neurons in the pons beneath the 4th ventricle. The LC is responsible for the majority of

norepinephrine neuronal input in most brain regions.4 It has axons which extend to a number of sites including the cerebellum, thalamus, hypothalamus, cerebral cortex,

and hippocampus. A single LC neuron can effect a large target area. Stimulation of LC neurons results in a number of different effects depending on the post-synaptic

cell. For example, stimulation of hippocampal pyramidal cells with norepinephrine results in an increase in post-synaptic activity. The LC is part of the ascending reticular

activating system which is known to be involved in the regulation of attention, arousal, and the sleep-wake cycle. Electrical stimulation of the LC in rats results in

hyper-responsive reactions to stimuli (visual, auditory, tactile, etc.)5 LSD has been found to enhance the reactivity of the LC to sensory stimulations. However, LSD was

not found to enhance the sensitivity of LC neurons to acteylcholine, glutamate, or substance P.6 Furthermore, application of LSD to the LC does not by itself cause

spontaneous neural firing. While many of the effects of LSD can be described by its effects on the LC, it is apparent that LSD’s effects on the LC are indirect.4 While

norepinephrine activity throughout the brain is mainly mediated by the LC, the majority of serotonergic neurons are located in the Raphe Nuclei (RN). The RN is located

in the middle of the brainstem from the midbrain to the medulla. It innervates the spinal cord where it is involved in the regulation of pain. Like the LC, the RN innervates

wide areas of the brain. Along with the LC, the RN is part of the ascending reticular activating system. 5-HT inhibits ascending traffic in the reticular system; perhaps

protecting the brain from sensory overload. Post-synaptic 5-HT receptors in the visual areas are also believed to be inhibitory. Thus, it is apparent that an interruption of

5-HT activity would result in disinhibition, and therefore excitation, of various sensory modalities. Current thought is that the mechanism of LSD is related to the regulation

of 5-HT activity in the RN. However, the RN is also influenced by GABAergic, catecholamergic, and histamergic neurons. LSD has been shown to also have affinities

for many of these receptors. Thus it is possible that some of its effects may be mediated through other pathways. Current research however has focused on the effects of

LSD on 5-HT activity. Before specific mechanisms and theories are discussed, a brief discussion of the principles of synaptic transmission will be given. Overview of

Synaptic Transmission There are two types of synapses between neurons: chemical and electrical. Chemical synapses are more common and are the type discussed in

this paper. When an action potential (AP) travels down a pre-synaptic cell, vesicles containing neurotransmitter are released into the synapse (exocytosis) where they

effect receptors on the post synaptic cell. Synaptic activity can be terminated through reuptake of the neurotransmitter to the pre-synaptic cell, the presence of enzymes

which inactivate the transmitter (metabolism), or simple diffusion. A pre-synaptic neuron can act on the post-synaptic neuron through direct or indirect pathways. In a

direct pathway, the post-synaptic receptor is also an ion channel. The binding of a neurotransmitter to its receptor on the post-synaptic cell directly modifies the activity of

the channel. Neurotransmitters can have excitatory or inhibitory effects. If a neurotransmitter is excitatory, it binds to a ligand activated channel in the post-synaptic cell

resulting in a change in membrane permeability to ions such as Na+ or K+ resulting in a depolarization which therefore brings the post-synaptic cell closer to threshold.

Inhibitory neurotransmitters can work post-synaptically by modifying the membrane permeability of the post-synaptic cell to anions such as Cl- which results in

hyperpolarization. Many neurotransmitters that have system-wide effects such as epinephrine (adrenaline), norepinephrine (noradrenaline), and 5-HT work by an indirect

pathway. In an indirect pathway, the post-synaptic receptor acts on an ion channel through indirect means such as a secondary messenger system. Many indirect

receptors such as muscarinic, Ach, and 5-HT involve the use of G proteins.5 Indirect mechanisms often will alter the behavior of a neuron without effecting its resting

potential. For example, norepinephrine blocks slow Ca activated K channels in the rat hippocampal pyramidal cells. Normally, Ca influx eventually causes the K channels

to open. This causes a prolonged after hyperpolarization which extends the refractory period of the neuron. Therefore, by blocking the K channels, the prolonged after

hyperpolarization is inhibited which results in the neuron firing more APs for a given excitatory input.5 Other indirect means of neuromodulation include interfering with

pre-synaptic neurotransmitter synthesis, storage, release, or reuptake. Inhibiting the reuptake of a neurotransmitter, for example, can cause an excitatory response.

Stimulation of neurotransmitter receptors can have a variety of effects on both pre and post-synaptic cells. Pre-synaptic receptors are sometimes involved in self

regulation while post-synaptic receptors can cause an increase (excitation) or decrease (inhibition) of AP firing in a neuron. A subtler method of neuromodulation involves

molecules that effect these neuroreceptors. Molecules that excite a receptor are referred to as agonists while those that interfere with receptor binding are called

antagonists. For example, 5-HT often acts as an inhibitory neurotransmitter. A 5-HT receptor antagonist could interfere with the activation of post-synaptic 5-HT

receptors causing them to be less responsive to inhibition. This disinhibition would make the post-synaptic cell more responsive to neural inputs, most likely resulting in an

excitatory response. Theory: LSD Pre-synaptically Inhibits 5-HT Neurons Raphe Nuclei neurons are autoreactive; that is they exhibit a regular spontaneous firing rate

that is not triggered by an external AP. Evidence for this comes from the observation that RN neural firing is relatively unaffected by transections isolating it from the

forebrain. Removal of Ca++ ions, which should block synaptic transmission, also has little effect on the rhythmic firing pattern. This firing pattern however is susceptible to

neuromodulation by a number of transmitters.7 In 1968, Aghajanian and colleagues observed that systemic administration of LSD inhibited spontaneous firing of these

autoreactive serotonergic neurons in the RN. Serotonergic neurons are known to have a negative feedback pathway through autoreceptors (receptors on the

pre-synaptic cell that respond to the neurotransmitter released by the cell). This means that an increase in 5-HT levels causes a decrease in the activity of serotonergic

neurons. Serotonergic neurons are also known to make synaptic connections with other RN neurons. This could have the result of spreading out the effects of negative

feedback to other RN neurons. This led to the theory that LSD causes a depletion of 5-HT through negative feedback in pre-synaptic autoreceptors.7 The depletion of

5-HT was thought to be responsible for the effects on the previously described systems innervated by the serotonergic neurons. A number of subsequent observations

have called this theory into doubt however. Low doses of LSD effect behavior but do not depress firing in the RN.8 The behavioral effects of LSD outlast the

modification of RNN firing.8 While repeated dosage of LSD results in a decrease of behavioral modifications (tolerance), its effects on the RN are unchanged.8 Other

hallucinogens such as mescaline and DOM do not effect R neurons.8 Depletion of 5-HT does not eliminate the effectiveness of LSD. If LSD worked by inhibiting the

5-HT output of pre-synaptic 5-HT neurons, it should be ineffaceable if 5-HT is depleted. The opposite result was actually observed; depletion enhances LSD activity.9

Mianserin, a 5-HT2 receptor antagonist, blocks LSD behavior but does not block LSD’s depression of RN neurons.9 While LSD does cause a decrease in the

autoreactive firing of RN neurons, this appears to be an effect and not the cause. These observations are considered however to be compatible with a post-synaptic

model. Subsequent research found that LSD and other hallucinogens have a high affinity for post-synaptic 5-HT1 and 5-HT2 receptors. In fact there is significant

correlation between the affinity of a hallucinogen for these receptors and its human potency. While it seems logical that 5-HT activity is modulated at 5-HT receptor sites,

it is possible that LSD could be affecting 5-HT receptor activity indirectly through adrenic or dopaminic pathways. However, blocking these receptors caused no change

in LSD’s activity on the 5-HT receptors, thus it appears that 5-HT activity is indeed modified by 5-HT receptors.10 While evidence indicates that LSD is a 5-HT1

agonist, it is debated whether the effects on 5-HT2 receptors is agonistic or antagonistic.11 Theory: LSD Post-synaptically Antagonizes 5-HT2 Receptors Initial

post-synaptic theories postulated that LSD was a 5-HT2 agonist. Pierce and Peroutka (P&P), however, argued that LSD has a number of antagonistic properties and

called into doubt some of the evidence presented as being compatible with agonist activity. The primary evidence for agonistic behavior comes from observations that the

effects of LSD are inhibited by 5-HT2 antagonists. P&P pointed out that this is not always the case. For example, some 5-HT2 antagonists such as spiperone do not

block LSD behavior. In addition, radioligand binding studies have shown that the affinity of 5-HT2 receptor agonists is pH dependent while the affinity of 5-HT2 receptor

antagonists and LSD are pH independent.9 5-HT2 receptors are connected to a phosphatidylinositol (PI) second messenger system. PI turnover has been found to be

stimulated by 5-HT and antagonized by 5-HT2 antagonists. P&P found that nM concentrations of LSD do not stimulate PI turnover. Therefore, LSD does not act as a

classic agonist. They also found that nM concentrations of LSD inhibited the stimulatory effect of 10M 5-HT. The ability of LSD to inhibit a concentration 1000x greater

is consistent with it being a 5-HT2 antagonist P&P also point out that the excitatory effects of 5-HT on CNS neurons appears to be caused by a decrease in K+

conductance attributable to activation of 5-HT2 receptors. P&P found that LSD inhibits this effect in rat somatosensory pyramidal neurons. This also is evidence that

LSD acts in an antagonistic role.9 The final line of evidence presented by P&P was from smooth muscle studies. The guinea pig trachea contracts when M concentrations

of 5-HT are present. The ability of 5-HT antagonists to inhibit this effect correlates with the antagonists affinity for the 5-HT2 binding site. Thus it appears that this muscle

contraction is 5-HT2 mediated. It was found that nM concentrations of LSD did not cause muscle contraction and inhibited the agonistic effects of M concentrations of

5-HT. This also is compatible with the actions of an antagonist. Theory: LSD Post-synaptically Partially Agonizes 5-HT Receptors Many of the apparent contradictions

in evidence in the debate over whether LSD acts as a 5-HT2 agonist or antagonist can be reconciled by the theory that LSD acts as a partial 5-HT2 agonist. Dr. Glennon

presented a number of arguments for this theory including data from his own research and from the studies discussed by P&P in the previous section. One of the primary

tools used by Glennon to determine the effects of various chemicals on the interactions between LSD and 5-HT was drug discrimination training in rats. Rats were trained

to discriminate 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (DOM) from saline. Training with DOM stimuli generalized to many indolealkylamine and

phenalkylamine hallucinogens. DOM was chosen instead of LSD as a training drug because of concern that LSD had a number of pharmacological effects. It was thought

that if the rat was trained with LSD, it might makes discriminations based on one of the pharmacological effects of LSD other than its effects on 5-HT. With this tool,

Glennon demonstrated that a number of 5-HT2 antagonists inhibited the ability of rats to discriminate LSD from saline. This indicates that LSD acts as a 5-HT2 agonist.

Glennon offered no explanation for P&P’s observation that some antagonists such as spiperone do not have this effect. However, spiperone and a few other similar

antagonists appear to only be about 40% effective in inhibiting 5-HT2 sites due to its relative nonselectivity.13 As discussed in the previous section, PI turnover has been

found to be stimulated by 5-HT and is antagonized by 5-HT2 antagonists. In another study of the effects of LSD on PI turnover, it was found that LSD acted as a partial

agonist (it produces approximately 25% of the effect caused by 5-HT). The apparent difference between this second study and P&P’s is that the second study tested the

effects at a variety of doses. From this it was concluded that while LSD has a higher affinity for 5-HT receptors than 5-HT does, it has a lower efficacy. This is

compatible with P&P’s observation that nM concentrations of LSD inhibited the stimulatory effects of uM 5-HT. If LSD acted as a partial agonist with low efficacy, it

could compete with 5-HT in binding to 5-HT2 receptors. Since 5-HT is a more potent agonist than the LSD, the effects of LSD would appear antagonistic. Glennon

argued that the guinea pig trachea may not be a good example since 5-HT does not work through a PI mechanism in this case. In the rat aorta, however, 5-HT does

hydrolize PI and the contractile effects of 5-HT are antagonized by ketanserin (a 5-HT2 antagonist). While LSD was not tested, another hallucinogen, DOB, was found

to have an agonistic effect that could be antagonized by ketanserin. This suggests that LSD acts agonistically in the rat aorta. Glennon points out that it may well be the

case that in other cases, the effects may be antagonistic. However, these effects could be explained if LSD had a low efficacy for the receptor. Hyperthermia and platelet

aggregation are both affected by 5-HT2 mechanisms. Hallucinogens such as LSD have been shown to behave agonistically and in the case of platelets, to be antagonized

by 5-HT2 antagonists such as ketanserin.11 LSD often has a biphasic response in which low doses have the opposite effects of higher doses. The head twitch response

in rodents is believed to be 5-HT2 mediated. At low doses, it has been found that LSD elicits a head-twitch response while at higher doses it antagonizes the response.

The rat startle reflex is amplified at low dosages of LSD while decreased at higher doses. This biphasic behavior can also be explained if LSD behaves as a partial

agonist.11 In summary, this theory claims that: “LSD is a high-affinity, low efficacy, nonselective 5-HT agonist; in the absence of another agonist it may function as an

agonist, whereas in the presence of a high efficacy agonist, it will function as an antagonist.” 11 Theory: LSD Post-synaptically Agonizes 5-HT1 Receptors Glennon also

gave another possible explanation for the antagonistic activity of LSD. There is some evidence that 5-HT1 receptors have an antagonistic relationship with 5-HT2

receptors. As discussed in the previous section, head twitch behavior is believed to be 5-HT2 mediated. DOI acts as a 5-HT2 agonist and elicits head twitch. 5-OMe

DMT also is a 5-HT agonist but has less efficacy than DOI. If the subject is pretreated with 5-OMe DMT, the effects of DOI are attenuated (because many of the

receptors are filled with the lower efficacy 5-OMe DMT molecules.) It has been found that A 5-HT1 agonist (8-OH DPAT) can also cause DOI attenuation. Other

studies have also demonstrated that 5-HT1 agonists can behave functionally as 5-HT2 antagonists.11 Glennon argued that this theory is lent extra credence from the

observation that 5-HT2 and 5-HT1c have similar relationships with various hallucinogens. A number of these hallucinogens have been shown to be 5-HT1c agonists.

Like 5-HT2 sites, the affinity of hallucinogens for 5-HT1c sites correlates with their hallucinogenic potency in humans. Thus another explanation of the biphasic behavior

of LSD is that increasingly higher doses of LSD cause increased antagonism of the 5HT2 receptor through agonism of 5HT1 receptors. Although, the pre-synaptic theory

seems to be fairly well discredited, it is interesting to note that there is debate as to whether pre-synaptic serotonin autoreceptors are of the 5-HT1 type. Whether

serotonergic autoreceptors are 5-HT1 or not, it has been demonstrated that there are also post-synaptic 5HT-1 receptors.12 While the role of these receptors is not

completely known, some researchers have hypothesized that 5-HT1 receptors may be involved in the regulation of norepinephrine.13 As discussed previously, the

majority of norepinephrine neurons are located in the LC which also has system wide innervation. Recent research on 5-HT receptors calls the theory that 5-HT1

agonism results in 5-HT2 antagonism into question. Since Glennon’s paper, the 5-HT1c receptor has been reclassified as 5-HT2c. Since the 5-HT2 receptors discussed

in this paper belong to the same family as what was called the 5-HT1c receptor, these have been reclassified as 5-HT2a.14 Since “5-HT1c” is a member of the 5-HT2

family, it is not surprising the LSD affinities are similar for the two receptors. While these reclassifications do not necessarily discount the theory that one receptor has an

antagonistic effect on the other, it seems likely that the evidence for this may need to be re-evaluated in terms of recent findings. Conclusion The lack of understanding

about the mechanisms of LSD is indicative of the problems involved in the bridging of the worlds of psychology and neurobiology. As more is learned about the roles and

interactions of various neurotransmitters, receptors, and on a larger scale: portions of the brain, the mystery will be further unraveled. With this caveat emptor firmly in

mind, it seems that the best explanation of LSD’s effects is that it behaves as a high affinity partial 5-HT agonist. Depending on the presence of other molecules and its

own concentration, LSD can have either agonistic or antagonistic effects on post-synaptic 5-HT2 family receptors. This modulation of 5-HT behavior is probably

responsible for many of the effects attributable to LSD. LSD also has an affinity for other neurotransmitter receptors that play important roles in the brain stem such as

norepinephrine, dopamine, and histamine. It is also hypothesized that LSD may modulate neural responses to these transmitters through its activity on 5-HT1 receptors.

Both the Locus Coeruleus and the Raphe Nuclei are part of the ascending reticular activating system which is implicated in the sensory modalities. The inhibition of 5-HT

in the RN and release of norepinephrine from LC neurons results in a flood of information from the sensory system reaching the brain. Some of the cognitive effects of

LSD could be attributed to the effects of brain stem innervation to areas of the brain such as the cerebral cortex and the hippocampus. References 1.(1995): “FAQ-LSD”

From internet newsgroup: alt.drugs.psychedelics 2.Sankar (1975): “LSD: A Total Study” 3.Ashton H (1987): “Brain Systems Disorders and Psychotropic Drugs”

4.Snyder (1986): “Drugs and the Brain” Sci Am Books Inc. From FAQ-LSD 5.Nicholls J, Martin R, Wallace B (1992): “From Neuron to Brain: Acellular andMolecular

Approach to the Function of the Nervous System” 6.Aghajanian GK(1980): “Mescaline and LSD Facilitate the Activation of Locus Coeruleus Neurons by Peripheral

Stimulation” Brain Res 186:492-496 7.Jacobs, B (1985): “An Overview of Brain Serotonergic Unit Activity and its Relevance to the Neuropharmacology of Serotonin.”

From: Green, A: Neuropharmacology of Serotonin 8.Jacobs, B, Trulson M, Heym J, (1981): “Dissociations Between the Effects of Hallucinogenic Drugs on Behavior

and Raphe Unit Activity in Freely Moving Cats” Brain Res 215:275-293 9.Pierce P, Peroutka S (1990): “Antagonist Properties of d-LSD at 5-Hydroxytryptamine2

Receptors”. Neuropsychopharmacolgy 3(5-6):509-517 10.Moret C (1985): “Pharmacology of the Serotonin Autoreceptor” From: Green, A: Neuropharmacology of

Serotonin 11.Glennon R (1990): “Do Classical Hallucinogens Act as 5-HT2 Agonists or Antagonists?” Neuropsychopharmacolgy 3(5-6):509-517 12.Green R, Heal D

(1985): “The Effects of Drugs on Serotonin Mediated Behavioral Models” From Green, A: Neuropharmacology of Serotonin 13.Leysen J (1985): “Characterization of

serotonin receptor binding sites” From Green, A: Neuropharmacology of Serotonin 14.Borne R. (1994) “Serotonin: The Neurotransmitter for the 90?s” URL:

http://www.fairlite.com/ocd/artiles/ser90.shtml. From: Drug Topics Oct, 10 1994:108

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