grammychronic
April 18th, 2009, 06:06 PM
by Jon Gettman
July 11, 1997
Recent research published in the journal Science provides valuable contributions to understanding the relative dependence liability of marijuana. (Tanda et al, 1997, de Fonseca et al, 1997)
Research by Tanda, Pontieri, and Di Chiara on cannabinoid activation of dopamine transmission is especially important. E. L. Gardner and this research team have been reporting on a cannabinoid effect on the brain reward system (Gardner et al, 1988a; Gardner et al, 1988b) and dopamine transmission for several years (Chen, et al 1990a; Chen et al 1990b; Chen et al 1993), however until now their results have not been replicated and similar experiments have been contradictory. (Castaneda et al, 1991)
Di Chiara and Imperato have previously associated an effect on dopamine with amphetamine, cocaine, ethanol, nicotine, and opiates. (Di Chiara, G. and Imperato, 1988) The key location of dopamine transmission is the nucleus accumbens. Recently a distinction has been discovered between the shell of the nucleus accumbens, which influences emotions, and a core, which influences somatomotor functions. (Heimer, L et al, 1991.) Nicotine, cocaine, amphetamines, and morphine have previously been shown to stimulate dopamine transmission in the shell of the nucleus accumbens. (Pontieri, F. E. et al 1996)
Abood and Martin note that Gardner's findings were confined to "one strain of rat" and its application "to human abuse is tentative at best." (Abood and Martin, 1992) This conclusion is also reported by the Office of Technology Assessment, which attributes the finding to an in-bred quality specific to Lewis Rats. (US Congress OTA, 1993)
In 1991 a research team of D.E. Moss published "THC does not affect striatal dopamine release: microdialysis in freely moving rats" (Castenada et al, 1991) which reported results from in vivo microdialysis on Long-Evans rats. In 1992 Herkenham, using a lesion-technique, established that there are no cannabinoid receptors in the dopamine producing areas of the brain. (Herkenham, 1992) These results were consistent with prior research indicating that animals will not self-administer marijuana.
The Office of Technology Assessment (OTA) reached the following conclusion about marijuana's abuse potential in 1993: "While marijuana produces a feeling of euphoria in humans, in general, animals will not self-administer THC in controlled studies. Also, cannabinoids generally do not lower the threshold needed to get animals to self-stimulate the brain reward system, as do other drugs of abuse." (US Congress OTA, 1993)
http://www.ukcia.org/research/gettman.htm
July 11, 1997
Recent research published in the journal Science provides valuable contributions to understanding the relative dependence liability of marijuana. (Tanda et al, 1997, de Fonseca et al, 1997)
Research by Tanda, Pontieri, and Di Chiara on cannabinoid activation of dopamine transmission is especially important. E. L. Gardner and this research team have been reporting on a cannabinoid effect on the brain reward system (Gardner et al, 1988a; Gardner et al, 1988b) and dopamine transmission for several years (Chen, et al 1990a; Chen et al 1990b; Chen et al 1993), however until now their results have not been replicated and similar experiments have been contradictory. (Castaneda et al, 1991)
Di Chiara and Imperato have previously associated an effect on dopamine with amphetamine, cocaine, ethanol, nicotine, and opiates. (Di Chiara, G. and Imperato, 1988) The key location of dopamine transmission is the nucleus accumbens. Recently a distinction has been discovered between the shell of the nucleus accumbens, which influences emotions, and a core, which influences somatomotor functions. (Heimer, L et al, 1991.) Nicotine, cocaine, amphetamines, and morphine have previously been shown to stimulate dopamine transmission in the shell of the nucleus accumbens. (Pontieri, F. E. et al 1996)
Abood and Martin note that Gardner's findings were confined to "one strain of rat" and its application "to human abuse is tentative at best." (Abood and Martin, 1992) This conclusion is also reported by the Office of Technology Assessment, which attributes the finding to an in-bred quality specific to Lewis Rats. (US Congress OTA, 1993)
In 1991 a research team of D.E. Moss published "THC does not affect striatal dopamine release: microdialysis in freely moving rats" (Castenada et al, 1991) which reported results from in vivo microdialysis on Long-Evans rats. In 1992 Herkenham, using a lesion-technique, established that there are no cannabinoid receptors in the dopamine producing areas of the brain. (Herkenham, 1992) These results were consistent with prior research indicating that animals will not self-administer marijuana.
The Office of Technology Assessment (OTA) reached the following conclusion about marijuana's abuse potential in 1993: "While marijuana produces a feeling of euphoria in humans, in general, animals will not self-administer THC in controlled studies. Also, cannabinoids generally do not lower the threshold needed to get animals to self-stimulate the brain reward system, as do other drugs of abuse." (US Congress OTA, 1993)
http://www.ukcia.org/research/gettman.htm