Analysis of the antinociceptive effect of the proanthocyanidin-rich fraction obtained from Croton celtidifolius barks: evidence for a role of the dopaminergic system.
In a previous study, we demonstrated the antinociceptive effect of 63SF, a proanthocyanidin-rich fraction obtained from Croton celtidifolius barks, in chemical and thermal behavioural models of pain in mice. The current study now investigate the possible mechanisms underlying the antinociceptive activity of 63SF in the formalin test, by using drugs which interfere with systems that are implicated in descending control of nociception. The antinociceptive effect of 63SF (11 mg/kg, i.p., given 30 min prior to 2.5% formalin) was not altered by pre-treatment of animals 45-50 min beforehand with either prazosin (alpha(1)-adrenergic antagonist; 0.15 mg/kg, i.p.), yohimbine (alpha(2)-adrenergic antagonist; 0.15 mg/kg, i.p.), ketanserin (5-HT(2A)-receptor antagonist; 1.0 mg/kg, i.p.), or l-arginine (substrate for NO synthase, 600 mg/kg, i.p.). On the other hand, treatment with sulpiride, an antagonist of dopaminergic D(2)-receptors (1.0 mg/kg, i.p., 45 min of pre-treatment), reversed the antinociceptive activity of 63SF. Pre-treatment of animals with reserpine (5 mg/kg, i.p., 24 h beforehand) did not alter the antinociceptive effect of 63SF. The current results support the view that the 63SF exerts antinociceptive effects by enhancing the activity of descending control, possibly by direct stimulation of dopaminergic D(2) receptors.
DalBó
Silvia
S
Departamento de Farmacologia, Centro de Ciências Biológicas, Bloco D, UFSC, Campus Universitário, Trindade, Florianópolis, SC, CEP 88040-900, Brazil.
Jürgensen
Sofia
S
Horst
Heros
H
Soethe
Douglas Nihues
DN
Santos
Adair Roberto Soares
AR
Pizzolatti
Moacir Geraldo
MG
Ribeiro-do-Valle
Rosa Maria
RM
D000700:Analgesics / Q000494:pharmacology*; D000818:Animals; D001120:Arginine / Q000494:pharmacology; D029802:Croton / Q000737:chemistry*; D008297:Male; D051379:Mice; D009569:Nitric Oxide / Q000502:physiology; D010936:Plant Extracts / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D044945:Proanthocyanidins / Q000494:pharmacology*; D017448:Receptors, Dopamine D2 / Q000502:physiology*; D013469:Sulpiride / Q000494:pharmacology; D015016:Yohimbine / Q000494:pharmacology
D000700:Analgesics; D010936:Plant Extracts; D044945:Proanthocyanidins; D017448:Receptors, Dopamine D2; C013221:proanthocyanidin; D015016:Yohimbine; D009569:Nitric Oxide; D013469:Sulpiride; D001120:Arginine; D011224:Prazosin