Caffeine - Caffeine Caffeine Most widely used psychoactive...

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Unformatted text preview: Caffeine Caffeine Most widely used psychoactive drug, over nicotine and alcohol Belongs to family of drugs known as methylxanthines Caffeine (Lots in coffee) Theobromine (found in chocolate) Theophylline (found in tea) Central nervous system stimulant Other Sources Chocolate: Theobroma cacao 1.5 oz Hershey bar 1.5 oz Hershey's Special Dark 10 mg 31 mg OTC medication Excedrin, 2 tablets 130 mg Coffee- Bean type Arabica Robusta ~ 80-100mg ~100-150mg Coffee History 850 Coffee berries discovered in Ethiopia Next, transplanted to Arabia ( Arabica....) Coffee Plant According to one story, the effect of coffee beans on behavior was noticed by a sheep herder from Caffa Ethopia named Kaldi as he tended his sheep (or goats). He noticed that the sheep became hyperactive after eating the red "cherries" from a certain plant when they changed pastures. He tried a few himself, and was soon as overactive as his herd. The story relates that a monk happened by and scolded him for "partaking of the devil's fruit." However the monks soon discovered that this fruit from the shiny green plant could help them stay awake for their prayers. Chemistry Xanthines 1,3,7-trimethylxanthine 3,7-dimethylxanthine Pharmacokinetics - Oral administration - Well-absorbed - Easily crosses BBB, placenta - Maximal central effects: ~ 2 h - Rapidly metabolized by liver - Active metabolites - Half-life: ~ 4 h Physiological Effects of Caffeine Heart rate Blood flow shifts to muscle Dilation of pupils Bronchial dilation Urination Cerebral vasoconstriction - Can relieve headaches Behavioral Effects of Caffeine Elevates mood Alertness Energy Mental performance Physical performance Fatigue Sleep Does not sober you after drinking! Adverse Effects Nervousness Insomnia, restlessness "Jitters" Nausea Delicate muscular coordination & timing GI disturbances Toxic effects "Caffeinism" 1g = 10 cups over a short time may be toxic Tachycardia Restlessness Anxiety or panic attacks Convulsions Lethal dose: 5-10g = 40-80 cups, though death is rare Overdose: >1000mg/day Caffeine addiction Tolerance Withdrawal Desire to quit Continued use despite problems Decaf ? Brain regions Highly Sensitive to Caffeine Cerebral cortex (Many neurotransmitters) Basal Ganglia - Caudate nucleus: locomotor activity nucleus - Nucleus accumbens: addiction and accumbens reward (Dopamine) Medulla - Raphe nuclei and locus coeruleus: sleep and mood (Serotonin) Mechanisms of action 1. Adenosine receptor antagonist 1. GABA receptor antagonist 1. cAMP breakdown inhibitor What is Adenosine? 1. Adenosine 1. Is a Xanthine + Sugar 2. `By-Product' of metabolism, second messengers, DNA... 3. Is a Neuromodulator (Metabotropic) Adenosine receptors in Brain Are Pre-synaptic Are Inhibitory- decrease Neurotransmitter release Fairly Ubiquitous Adenosine Xanthine moiety Pentose sugar moiety Vesicles containing norepinephrine Post synaptic receptors Adenosine receptors as inhibitors Vesicles containing adenosine Inhibiting Release of other neurotransmitters at presynaptic site Adenosine receptors X Vesicles containing norepinephrine Post synaptic receptors Adenosine receptor antagonist = Enhancing Neurotransmission Vesicles containing adenosine Caffeine blocking Adenosine receptors at the presynaptic site Adenosine receptors CAFFEINE Vesicles containing norepinephrine X X Post synaptic receptors Caffeine mechanism of action GABA receptor antagonist CAFFEINE VALIUM Caffeine: Phosphodiesterase Inhibitor Increase the effects of Second Messenger cAMP NT Receptor G- protein Ion channel C af Phosphodiesterase fe in e 2 Messengers How can caffeine affect disease states? Caffeine and disease Asthma: bronchodilator Pregnancy fetal blood flow birth weight SIDS Osteoporosis: urine Ca++ excretion Ca++ absorption Heart disease: ?? Cancer: ?? Coffee: The New Health Food? Lowers risk of Parkinson's disease Diabetes Colon cancer Cavities Liver cirrhosis Gallstones Parkinson's disease Adenosine receptor antagonist Vesicles containing adenosine Adenosine receptors CAFFEINE Vesicles containing dopamine Post synaptic receptors Caffeine-PD hypothesis ? Parkinson's disease Caffeine -Block adenosine receptors -Increase dopamine levels -Restore function ...
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This note was uploaded on 04/15/2008 for the course NROSCI 0081 taught by Professor Armandosignore during the Spring '08 term at Pittsburgh.

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