Paraxanthine: Connecting Caffeine to Nitric Oxide Neurotransmission.
Recent results obtained in our laboratory indicate that paraxanthine, the main metabolite of caffeine in humans, produces a significantly stronger locomotor activation in rats than caffeine. Furthermore, paraxanthine also produced a very significant increase in striatal extracellular concentrations of dopamine. Searching for an additional mechanism other than adenosine antagonism responsible for these psychostimulant-like effects, it was found that paraxanthine, but not caffeine, inhibited cGMP-preferring phosphodiesterases. Furthermore, interrupting nitric oxide neurotransmision (inhibiting nitric oxide synthase) significantly decreased both the locomotor-activating and the dopamine-releasing effects of paraxanthine. These results open up some obvious questions about the role of paraxanthine in the pharmacological effects of caffeine.
Intramural Research Program, Integrative Neurobiology Section, Department of Health and Human Services, National Institute on Drug Abuse , Baltimore, Maryland.
Sergi
S
Ferré
Intramural Research Program, Integrative Neurobiology Section, Department of Health and Human Services, National Institute on Drug Abuse , Baltimore, Maryland.
Marco
M
Orrú
Intramural Research Program, Integrative Neurobiology Section, Department of Health and Human Services, National Institute on Drug Abuse , Baltimore, Maryland.
Xavier
X
Guitart