Braida, D., E. Paladini, E. Gori and M. Sala.Naltrexone, naltrindole, and CTOP block cocaine-induced sensitization to seizures and death.Peptides 18(8) 1189-1195, 1997.-ICV injection for 9 days of either naltexone (NTX) (5, 10, 20, 40 μg/rat) or a selective μ peptide (CTOP) (0.125, 0.25, 0.5, 1, 3, 6 μg/rat) or δ (naltrindole) (NLT) (5, 10, 20 μg/rat) subtype opioid receptor antagonist affected sensitization to cocaine (COC) (50 mg/kg, IP) administered 10 min after. NTX (5 and 40 μg/rat), NLT (10 and 20 μg/rat), and the peptide CTOP (0.25-0.5 μg/rat) attenuated seizure parameters (percent of animals showing seizures, mean score and latency) in a day-related manner. The DD 5 0 (days to reach 50% of death) value for COC was 2.69, whereas it was 9.67 and 7.27 for NTX 5 and 40 μg/rat, 8.59 for NLT (10 μg/rat), and 6.11, 5.95, and 4.30 for CTOP (0.25, 0.5, and 1 μg/rat respectively). These findings suggest a concurrent involvement of μ- and δ-opioid receptor subtype in COC-induced sensitization to toxic effects.