lecture 23: alkaloids caffeine Flashcards
alkaloids
chemical compounds, basic nitrogen atoms
psychotropic and stimulant effects
caffeine, nicotine, cocaine, morphine
caffeine
psychostimulant
beans (seeds)
alkaloid produced by plants as a defense mechanism against invertebrate herbivores
physiological effects of caffeine
increase CNS stimulation, lipolysis, Ca2+ release in skeletal muscles
metabolism of caffeine
hydrophilic and crosses blood-brain barrier and placenta
metabolized into paraxanthine, theobromine, theophylline
caffeine and adenosine
structurally similar to adenosine - neurotransmitter in CNS
adenosine antagonist, blocks adenosine receptor, multiple adenosine receptor subtypes
adenosine receptors
different types of receptors, can stimulate or inhibit G-proteins > activation and inhibition of neural excitability
most pronounced caffeine-induced behavioral effect
increase in locomotor activity, linked to dose-dependent inhibition of AI and A2A receptors
stimulating effects and dopamine receptor
caffeine targets dopamine and adenosine receptors to block dopamine (excitatory molecule) inhibition
adenosine, binding of adenosine to A1 receptor
depressant function as a neurotransmitter
binding to A1 receptor inhibits D1 receptor activity, low cAMP, low PKA > low locomotor activity
how does caffeine promote locomotor activity?
binding of caffeine to A1 receptor > inhibition of adenosine signaling
no longer suppresses D1 activity > activation of adenyl cyclase > increased cAMP > increased PKA > increased locomotor activity
protein kinase A (PKA)
cAMP dependent protein kinase
fuel catabolism effect
inhibition of phosphodiesterase
caffeine inhibits phosphodiesterase enzymes which break down cAMP > caffeine inhibits cAMP degredation, increased duration of downstream effects (ex. lipolysis)
caffeine and intracellular Ca2+
caffeine can induce calcium release from the ER and inhibit reuptake
increase muscle contractility
intracellular Ca2+ > eNOS activation > NO > vasodilation > decrease BP, increase blood flow
increased oxygen movement > increase fuel utilization, metabolism of fats
theobromine
alkaloid in foods like cocoa
caffeine metabolized to theobromine after consumption
vasodilator, diuretic, stimulant
some of the same metabolic effects as caffeine but not as potent
What are the two ways caffeine can promote elevated cAMP levels within a caffeine-stimulated cell?
1) A1R binding to inhibit adenosine, increase of cAMP
2) inhibits phosphodiesterase which breaks down cAMP, inhibits breakdown of cAMP, longer duration
