In vivo brain microdialysis was used to assess the effects of tolcapone, a novel central and peripheral inhibitor of catechol-O-methyltransferase on striatal 3,4-dihydroxyphenyl-L-alanine (L-dopa) and dopamine metabolism. The oral administration of 30 mg/kg of tolcapone failed to change dopamine output but elicited a marked and long-lasting decrease of the extracellular levels of homovanillic acid (HVA) and 3-methoxytyramine with a concomitant increase of 3,4-dihydroxyphenylacetic acid (DOPAC). The administration of L-dopa (20 and 60 mg/kg p.o.) + benserazide (15 mg/kg p.o.) resulted in dose-dependent increase of dialysate levels of L-dopa and 3-O-methyl-DOPA. Tolcapone (30 mg/kg p.o.), given as adjunct to both doses of L-dopa, markedly enhanced the elevation or extracellular L-dopa, while it completely prevented the formation of 3-O-methyl-DOPA. In another experiment, the administration of L-dopa + benserazide (30 + 15 mg/kg p.o.) resulted in increased extracellular levels of dopamine, DOPAC, HVA and 3-methoxytyramine. The co-administration of tolcapone (30 mg/kg p.o.) further increased dopamine and DOPAC levels, whereas HVA and 3-methoxytyramine effluxes were reduced. These findings support the notion that tolcapone has the ability to enhance striatal dopamine neurotransmission by increasing L-dopa bioavailability through peripheral and central inhibition of L-dopa O-methylation, as well as by blocking the central conversion of dopamine into 3-methoxytyramine.
In vivo brain microdialysis was used to assess the effects of tolcapone , a novel central and peripheral inhibitor of catechol - O - methyltransferase on striatal 3,4-dihydroxyphenyl - L - alanine ( L - dopa ) and dopamine metabolism . The oral administration of 30 mg / kg of tolcapone failed to change dopamine output but elicited a marked and long - lasting decrease of the extracellular levels of homovanillic acid ( HVA ) and 3-methoxytyramine with a concomitant increase of 3,4-dihydroxyphenylacetic acid ( DOPAC ) . The administration of L - dopa ( 20 and 60 mg / kg p.o . ) + benserazide ( 15 mg / kg p.o . ) resulted in dose - dependent increase of dialysate levels of L - dopa and 3-O - methyl - DOPA . Tolcapone ( 30 mg / kg p.o . ) , given as adjunct to both doses of L - dopa , markedly enhanced the elevation or extracellular L - dopa , while it completely prevented the formation of 3-O - methyl - DOPA . In another experiment , the administration of L - dopa + benserazide ( 30 + 15 mg / kg p.o . ) resulted in increased extracellular levels of dopamine , DOPAC , HVA and 3-methoxytyramine . The co - administration of tolcapone ( 30 mg / kg p.o . ) further increased dopamine and DOPAC levels , whereas HVA and 3-methoxytyramine effluxes were reduced . These findings support the notion that tolcapone has the ability to enhance striatal dopamine neurotransmission by increasing L - dopa bioavailability through peripheral and central inhibition of L - dopa O - methylation , as well as by blocking the central conversion of dopamine into 3-methoxytyramine .
Which drug is benserazide usually co-administered with?
Which drug is benserazide usually co - administered with ?
L-Dopa
L-Dopa