{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Lecture13 - BioNB222 Cornell University Spring 2008 Ronald...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
BioNB222 Spring 2008 Cornell University Ronald Harris-Warrick 1 Lecture 13. Just Say “Know”: Effects of Street Drugs on the Brain Reading Assignment Purves et al., Chapter 6, especially the boxes on p. 139 and p. 147. Summary: Psychoactive drugs are a window into how the brain generates consciousness. They do not create any new physiological actions, but act by modifying processes that are always going on. By studying their mechanisms and sites of action, we gain further insights into normal brain function. Most psychoactive drugs act preferentially at synapses, and we will discuss their actions there. Stimulants such as cocaine, amphetamines and ecstasy act pre-synaptically to block the transporters that remove dopamine or serotonin from the synaptic cleft, thus prolonging the monoamines’ actions at their synapses. Ecstasy is neurotoxic at high concentrations, killing the serotonin nerve terminals which only slowly (or not at all) recover. Other drugs, including psychedelics such as LSD and opiates, act post-synaptically, mimicking normal transmitter actions to enhance the activity of serotonergic or endorphinergic pathways. Marijuana mimics the actions of the endogenously released endocannabinoids, and primarily binds to pre-synaptic terminals to block transmitter release. Alcohol acts much less selectively, affecting many transmitter systems to induce confusion, motor incoordination and eventually coma. Learning Objectives 1. To learn about the basic effects of cocaine, methamphetamine, ecstasy, LSD, marijuana and alcohol on normal perception and consciousness. 2. To learn the basic molecular targets of action of these drugs to start to understand how they act on the brain. 3. To begin to learn how these molecular actions result in changes in human consciousness. Lecture Outline A. Stimulants with a pre-synaptic action: Cocaine and the amphetamines Cocaine is typically extracted as a hydrochloride salt from the leaves of Erythroxylon coca . When extracted in ether to obtain the free base, it becomes crack which can be smoked. Amphetamines such as methamphetamine are drugs related to dopamine and also exist as a hydrochloride salt (“speed”) and a smokable form (“Ice”). Both drugs have similar actions to elevate mood, induce euphoria, increase alertness and reduce fatigue; however, a cocaine “high” usually lasts 30-60 minutes, while a methamphetamine trip lasts 12-24 hours.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
2 When smoked or injected, the “rush” is intensely pleasurable for a period of seconds to minutes. This is followed by a longer period of milder euphoria mixed with increased anxiety and a strong desire to obtain more of the drug. During this time, the user is also prone to acts of violence due to paranoia and anxiety. Upon repeated use over short times, a toxic paranoid psychosis can be evoked which is clinically indistinguishable from the florid early signs of schizophrenia: marked anxiety, sleep deprivation, suspiciousness, paranoia and persecutory fears are mixed with disordered and hallucinatory thoughts, vivid visual, auditory
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern