Cross-tolerance between morphine and clonidine: a study on motility in rats.
The effects of clonidine on motility were determined in non-dependent, morphine-dependent (a 20 mg/kg dose i.p. for 26 days) and post-dependent rats. In naive animals, clonidine (30-100 micrograms/kg) produced a dose-related suppression of motility. However, when the drug was administered in morphine-dependent rats, it induced slight hyperactivity at small doses and a decrease of activity only at the largest dose (100 micrograms/kg). Thus, tolerance to morphine conferred cross-tolerance to clonidine. On the contrary, the effects of clonidine on motility in post-dependent animals did not differ from those observed in control animals. The results are discussed in terms of similarities and differences between the depressant and excitatory effects of morphine and clonidine.
Bartoletti
M
M
Institute of Pharmacology, University of Bologna, Italy.
Gaiardi
M
M
Gubellini
C
C
Bacchi
A
A
Babbini
M
M
D000818:Animals; D003000:Clonidine / Q000494:pharmacology*; D004361:Drug Tolerance; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009021:Morphine Dependence / Q000523:psychology; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains
D009020:Morphine; D003000:Clonidine