Differential effects of apomorphine on spinal reflex activity following 6-hydroxydopamine or long-term haloperidol pretreatment.
The thermal cutaneous evoked tail flick response was measured both before and after intrathecal injection of R-apomorphine in spinal rats and in rats with an intact neuraxis pretreated with either long-term haloperidol or intrathecal 6-hydroxydopamine. Intrathecal R-apomorphine produced a dose-dependent increase of tail flick latency in spinal rats but not in intact rats. Long-term haloperidol treatment increased the effect of R-apomorphine in spinal rats while 6-OHDA decreased it. The present findings provide further evidence for the modulatory role of spinal DA receptor populations on spinal reflex activity. Pretreatment with long-term haloperidol or 6-OHDA may alter the conformational status of spinal DA receptors in opposite directions and thereby change the responsiveness of receptors to R-apomorphine.
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D004298:Dopamine / Q000378:metabolism; D006220:Haloperidol / Q000494:pharmacology*; D006892:Hydroxydopamines / Q000494:pharmacology*; D008297:Male; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D009638:Norepinephrine / Q000378:metabolism; D016627:Oxidopamine; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000187:drug effects; D012018:Reflex / Q000187:drug effects* / Q000502:physiology; D013116:Spinal Cord / Q000502:physiology
D006892:Hydroxydopamines; D011954:Receptors, Dopamine; D016627:Oxidopamine; D006220:Haloperidol; D001058:Apomorphine; D004298:Dopamine; D009638:Norepinephrine