title: Dynorphin A-(1-13) attenuates withdrawal in morphine-dependent rats: effect of route of administration.
abstract: Rats were made tolerant to morphine by subcutaneous implantation of morphine alkaloid pellets. Three days after pellet implantation, withdrawal was induced by pellet removal and was assessed 6 h later. Immediately prior to withdrawal assessment, rats were injected with dynorphin A-(1-13) either i.th. (via a catheter), i.c.v. (via a cannula) or i.v. (via the tail vein). When administered i.th. in the dose range 1.25-5 nmol/rat, dynorphin A-(1-13) attenuated withdrawal over the 40 min observation period. Similarly, dynorphin A-(1-13) administered i.v. (37.5-150 nmol/kg) attenuated withdrawal, though only over the first 20 min following administration. Dynorphin A-(1-13) up to 10 nmol/rat had no effect on withdrawal scores. These data indicate that dynorphin acts at spinal sites to suppress withdrawal in morphine-dependent rats and may play a role in tolerance and dependence mechanisms.
mesh_terms: D000818:Animals; D002408:Catheters, Indwelling; D004399:Dynorphins / Q000008:administration & dosage / Q000627:therapeutic use*; D007275:Injections, Intravenous; D007276:Injections, Intraventricular; D007278:Injections, Spinal; D008297:Male; D009020:Morphine / Q000009:adverse effects*; D009294:Narcotics / Q000008:administration & dosage / Q000627:therapeutic use*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000627:therapeutic use*; D051381:Rats; D011919:Rats, Inbred Strains; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy*; D014782:Visceral Prolapse / Q000139:chemically induced; D015000:Yawning
chemical_list: D009294:Narcotics; D010446:Peptide Fragments; C026843:dynorphin (1-13); D004399:Dynorphins; D009020:Morphine