Central action of narcotic analgesics. VIII. The effect of dopaminergic stimulants on the action of analgesics in rats.
We investigated the influence of apomorphine, amphetamine, amantadine, dimethylaminoadamantane, nomifensine, ergometrine and beta-phenylethylamine on cataleptogenic and antinociceptive action of analgesics in rats. Nomifensine, apomorphine, beta-phenylethylamine, amantadine and ergometrine antagonized the catalepsy induced by morphine and codeine. Catalepsy induced by fentanyl was depressed only by nomifensine and apomorphine. Amphetamine only slightly antagonized the analgesic-induced catalepsy and the effects were not dose-dependent. Dimethylaminoadamantane did not antagonize catalepsy at all. Antinociceptive action of morphine and codeine was antagonized by apomorphine and amphetamine. Ergometrine counteracted the action of morphine, and beta-phenylethylamine decreased the action of pentazocine. The results suggest that: 1. There are differences in the mechanism of cataleptogenic action of the opiates (morphine and codeine) and fentanyl; 2. Catalepsy after analgesia differs from the catalepsy produced by neuroleptics in respect of interaction with such drugs as amphetamine, apomorphine or dimethylaminoadamantane. Analgesic-induced catalepsy seems to depend on the presynaptic inhibition of dopaminergic neurotransmission; 3. Stimulation of the central dopaminergic system in rat brain either does not change or weakly antagonizes the action of analgesics in the hot plate test.
D000661:Amphetamine / Q000494:pharmacology; D000700:Analgesics / Q000494:pharmacology; D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D002375:Catalepsy / Q000139:chemically induced; D003061:Codeine / Q000494:pharmacology; D004298:Dopamine / Q000502:physiology*; D004347:Drug Interactions; D005283:Fentanyl / Q000494:pharmacology; D006801:Humans; D008297:Male; D009020:Morphine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D013997:Time Factors
D000700:Analgesics; D000701:Analgesics, Opioid; D009020:Morphine; D000661:Amphetamine; D001058:Apomorphine; D005283:Fentanyl; D003061:Codeine; D004298:Dopamine