Discrimination of morphine- and haloperidol-induced muscular rigidity and akinesia/catalepsy in simple tests in rats.
The present study was conducted to establish a simple method for measuring muscular rigidity in rats, which could be used for screening and is able to discriminate between rigidity and akinesia/catalepsy. Therefore, we treated rats with morphine (30 mg/kg i.p.), since large doses of morphine lead to muscular rigidity and akinesia. We measured muscular rigidity with a new method by determining the resistance of the hindlimb to passive flexion in the 'balance test' and also checked haloperidol (3 mg/kg i.p.) treated rats for muscular rigidity. Furthermore, catalepsy was also tested after administration of each of these drugs. Then, the influence of D(1)-like and D(2)-like dopamine receptor stimulation on muscular rigidity and catalepsy was studied. Therefore, the partial D(1) agonist SKF 38393 (3 and 8 mg/kg s.c.), the D(2)/D(1) agonist pergolide (0.25 and 0.5 mg/kg i.p.) and the dopamine precursor L-DOPA (50 and 100 mg/kg i.p.) were administered up to 30 min before muscular rigidity was measured in morphine-treated rats. The results showed that morphine, but not haloperidol led to muscular rigidity, whereas both drugs led to positive scores in the catalepsy test. The dopaminergic drugs partly antagonized the morphine-induced muscular rigidity in the doses applied, but not the catalepsy. Apparently, rigidity, akinesia/catalepsy produced by morphine can be discriminated from that produced by haloperidol in simple and quick tests.
Faculty of Pharmacy, Institute of Pharmacology and Toxicology, University of Marburg, Ketzerbach 63, D-35032 Marburg, Germany.
Daniel Alvarez
DA
Fischer
Boris
B
Ferger
Klaus
K
Kuschinsky
D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D002375:Catalepsy / Q000139:chemically induced* / Q000523:psychology; D004409:Dyskinesia, Drug-Induced / Q000523:psychology*; D006220:Haloperidol / Q000494:pharmacology*; D018737:Hand Strength / Q000502:physiology; D006614:Hindlimb / Q000502:physiology; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009127:Muscle Rigidity / Q000139:chemically induced* / Q000523:psychology; D004856:Postural Balance / Q000187:drug effects; D011187:Posture / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar
D000701:Analgesics, Opioid; D014150:Antipsychotic Agents; D009020:Morphine; D006220:Haloperidol