Dihydroergotoxine potentiation of thioridazine-induced hypomotility.
Dihydroergotoxine (DHET), a dopamine (DA) receptor agonist, induced hypomotility in rats at doses of 0.125-0.5 mg/kg s.c., (-)sulpiride a D-2 receptor antagonist, a dose which did not affect spontaneous activity (10 mg/kg s.c.) counteracted the hypomotility induced by DHET. Thioridazine (THR), a widely used neuroleptic, reduced motility (2.5-10 mg/kg i.p.) when given alone; this effect was potentiated by DHET when the two drugs administered in doses of 1 mg/kg THR/0.05 mg/kg DHET and 2.5 mg/kg THR/0.125 mg/kg DHET; higher doses of THR (5 and 10 mg/kg i.p.) which by themselves induced marked inhibition of motility, were not potentiated by doses of DHET of 0.25 and 0.5 mg/kg s.c. THR and DHET influenced in an opposite manner the levels of DA-metabolites dihydroxyphenylacetic acid and homovanillic acid in the caudate; while THR (1-10 mg/kg i.p.) increased, DHET (0.25-0.5 mg/kg s.c.), decreased DA-metabolite levels. The association of THD and DHET resulted in a reciprocal antagonism of their effects on DA-metabolite levels.
D015102:3,4-Dihydroxyphenylacetic Acid / Q000378:metabolism; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004088:Dihydroergotoxine / Q000494:pharmacology*; D004357:Drug Synergism; D006719:Homovanillic Acid / Q000378:metabolism; D008297:Male; D051379:Mice; D009043:Motor Activity / Q000187:drug effects*; D013881:Thioridazine / Q000494:pharmacology*
D015102:3,4-Dihydroxyphenylacetic Acid; D004088:Dihydroergotoxine; D013881:Thioridazine; D006719:Homovanillic Acid