Class Notes (839,195)
Canada (511,223)
Psychology (7,818)
PSYC62H3 (143)


11 Pages

Course Code
Suzanne Erb

This preview shows pages 1,2 and half of page 3. Sign up to view the full 11 pages of the document.
PSYC62: Drugs and the Brain Lecture 6: Psychostimulants The Psychostimulants  The major stimulants: 1) The Amphetamines o Dextroamphetamine  Active isomer of amphetamine molecule, can be taken orally or injected  Used to be allowed in over the counter medications, but not anymore  They do have medical applications, but are only prescribed for obesity, narcolepsy and ADHD treatments, also effective in treatment-resistant depression. o Methylphenidate (Ritalin)  Methylphenidate (Ritalin) - used very commonly in treatment of ADHA, discovered for treatment of ADHD in 1979 by Dr Charles Bradley who noticed that a dose of the stimulant could calm hyperactive kids  Millions of children and adults have been treated with it or a close analogue of it. It is a paradox that you are using a stimulant to treat a hyperactive behavior but to some degree this stimulant enhances self-control and attention by boosting certain systems that are active in a hypoactive state. o Methamphetamine  Most abused and amphetamine o Methcathinone  No approved medical uses (Schedule I)  Newest one 2) Cocaine o In 1970s, it became a drug of choice again o Use as local anesthetic, some forms of eye surgery o This is pretty much the only medicinal use, schedule II drug  The minor stimulants" 1) Nicotine o Not dangerous acutely and that's why it's in the minor category 2) Caffeine The Psychostimulants  Psychostimulants are drugs that increase alertness, heighten arousal, and cause behavioural excitement  Stimulant drugs like amphetamine and cocaine affect the brain primarily through actions on monoamine systems: dopamine (DA), norepinephrine (NE), and serotonin (5-HT) o These systems underlie virtually all emotional/motivational responses that mammals experience, drugs that have PROFOUND effects on cognitions/mental function  Stimulant drugs may be administered and absorbed in a number of different ways and their onsets of action vary accordingly o Intranasal, snorted, peak effects will vary depending on route. Psychostimulants that are absorbed more rapidly will have greater effect and therefore a greater abuse liability.  Stimulants differ with respect to their durations of action and abuse liability accordingly o E.g., Amphetamines much longer-acting than cocaine. o In general, the effects of amphetamines and cocaine are very similar in term of pharmacological profile o Their duration is the major distinction, cocaine is metabolized rapidly and its effects disappear kind of rapidly, whereas amphetamines are longer acting and the effects persist for several hours  Cocaine - smoking is a very rapid onset of effect and potent effect  Amphetamines are much longer acting drug than cocaine - behavioral effects of both are very similar  Cocaine is metabolized very rapidly and most of the effects dissipate in the first 20 to 80 minutes - half life of about 20 minutes  Amphetamine - can persist for hours The Psychostimulants  At low to moderate doses, psychomotor stimulants: o Produce motor stimulation o Reduce fatigue o Increase resistance to sleep  Insomnia is often an effect that occurs due to repeated administration o Increase vigilance and alertness o Induce a heightened mood or anxiety  Heightened positive and negative effects  These effects occur in low to moderate dose ranges, with higher doses you may get reverse effects? U shaped dose response curves.  At high doses effects may counter the motorizing effects induced in the low-moderate dose range  Psychomotor effects are mediated by the midbrain dopamine system  Motor activity is used as a index for other effects  If you give high doses of the drug - you actually have opposite effects - inverse relationship Psychostimulant Dependence  Psychostimulants produce profound dependence - the dependence is largely a psychological dependence and withdrawal  Primary symptoms associated with withdrawal: o Depression o Anxiety o Changes in appetite o Sleeping disturbances o Craving  Depression, anxiety, and craving are the ones that have been studied the most  Depression and anxiety in humans have been very strongly related to cocaine and amphetamines  In animal models - animals that are experiencing withdrawal from psychostimulants are extremely anxious - with the study of the (+) maze - the animal will spend less time in the open arms as opposed to animals that are not anxious  Rats may how heightened levels of anxiety when they are in withdrawal state  In the short term, the craving/wanting of more drug reflects the wanting to overcome the negative effect, but also they will seek out the drug in order to achieve the intense euphoria.  In the short term, acute withdrawal, negative and positive enforcement are at play.  Negative: strengthening of a behaviour to take something negative away (like the reduction of the negative affect).  Positive: the actual pull of the drug.  In the long term, the desire to take the drug again is associated primarily with positive reinforcement mechanisms, the desire to achieve the euphoria that the user knows the drug can produce. Psychostimulant Dependence  Phases of withdrawal: o Not all individuals will advance through all these phases of withdrawal because some will take the drug again 1) ―Crash‖ o Individual is absolutely exhausted o Exhaustion alternating with periods of anxiety and deep depression. Individual will sleep for long periods of time, show no desire to take the drug again o The pattern of taking psychostimulant drugs is binge o Take cocaine or amphetamine for a period of days, crash and stop taking for days, and then repeat o This distinguishes psychostimulant from other drugs o This binge pattern is also modeled in animals, e.g. rats who have unlimited access to cocaine. 2) Withdrawal o If the individual does not resume drug taking after the crash, they enter this second phase o Lasts for several weeks o During this period of time the addict experiences intense cravings for drugs, moderate to severe depression and an inability to experience pleasure (anhedonic state) o Because of this state and the cravings, individuals very often resume drug taking during this period. 3) Extinction o If they are able to maintain abstinence during withdrawal, they enter the extinction phase o This lasts for an indefinite period of time, from weeks, months, or even years o Addicts may experience intermittent cravings, but they don't take the drug o During this phase, individual is experiencing cues from the environment that makes them want to take the drug, but they don't resume drug taking o Over time, if they keep experiencing the cues but don't take the drug, the link between the cues and the craving will lessen to the point that over time, the cues will no longer lead to craving?  Methcathinone is actually a schedule one drug while the other amphetamines are schedule 2 AMPHETAMINES Amphetamines  Come in form of tablets, crystals, or powder o Swallowed, taken intranasally or smoked. o In powder form, it is mainly taken orally or intranasally o When used recreationally, it is called meth or speed o White crystalline and odorless powder can be prepared in tablet form, or it dissolves rapidly in water so it can be swallowed or injected  Can be swallowed, snorted, or smoked o The form that is smoked is called crystal meth, ice crystal or glass? o Consists of clear glass-looking crystals that can be smoked like crack cocaine, although crystal meth can also be dissolved? Amphetamines: Some Canadian statistics  In 2004, 6.4% of Canadians aged 15 and older had used amphetamines at least once in their lifetime. That represents over 1,500,000 people.  In 2002, 12.2% of street youth reported that amphetamines (speed, meth, crystal) were the type of substances most commonly used in the last three months Amphetamine: Pharmacology  Stimulates monoamine synapses by increasing the release of monoamines from the presynaptic terminal o Basic effect is to produce a storm of activity in neural pathways that are something to monoamines.  Blocks the re-uptake of monoamines via their protein transporters o Just like cocaine o Act as indirect agonists - hence more dopamine in the synapse  Reverses the actions of monoamine transporters o e.g., Reverses the DA transporter, causing the cell to excrete DA. o Induce or cause the release of dopamine into the synapse  Temporarily inhibits monoamine oxidase o MAO metabolizes monoamines in the pre-synaptic terminal o Amphetamine inhibits the action of this enzyme and interferes with the metabolism of monoamines in the presynaptic terminal and increases the availability of monoamines for release.  The rewarding effects of amphetamine are believed to be due primarily to the interference in the activity of the DA transporter Figure 1  Amphetamines result in an increase in [DA] at the synapse that is available for post-synaptic binding  In addition to blocking the uptake of DA, interacts with the transporter to increase the release of the NT into the synapse  Cocaine doesn't mess with this reverse transport business, that's unique to amphetamine Figure 2  Increase the availability of a naturally occurring transmitter  Exactly the same scenario that happens with cocaine. Presynaptic transporters mediate uptake of NT after their effects have occurred  What amphetamine does is to bind/block the effect of these transporters such that the amount of Dopa in the synapse accumulates  Acts just like cocaine Figure 3  Nucleus acumbens DA is highly implicated in the rewarding effects of amphetamine Amphetamine: Historical Perspective  Amphetamine marketing for medicinal purposes let to their use and abuse recreationally  Use of amphetamines increased in the years following the Harrison Narcotic Act (1914), which made cocaine a controlled substance o Amphetamine use increased as cocaine use decreased th  Amphetamines were first synthesized in the late 19 century; first medical applications developed in 1920’s  Amphetamines were first marketed in 1927 for the purposes of combating fatigue, heightening mood, and improving endurance o Doing these things for soldiers during WWII, amphetamine were readily prescribed to soldiers to increase their stamina o Amphetamine is still used for treatment of narcolepsy today o Amphetamine and cocaine are anorexic drugs, they can be prescribed for certain forms of obesity  Other early medicinal applications incl
More Less
Unlock Document

Only pages 1,2 and half of page 3 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.