1-(1-Naphthyl)piperazine (1-NP) has been reported to have
serotonin antagonist properties at the 5-HT2 subtype of receptor, and it has been suggested that it may have agonist actions at the 5-HT1 site. In the present experiments, the effects of 1-NP alone and in combination with a variety of
5-HT agonists, were studied in squirrel monkeys performing under a number of reinforcement schedules. The phenalkylamine
hallucinogen 4-bromo-2,5-dimethoxyamphetamine (DOB, 0.01-0.3 mg/kg), which is thought to have predominant actions at 5-HT2 sites, reduced responding under fixed-interval (FI) schedules of presentation of food, and these decreases were blocked by 1-NP (0.3-1.0 mg/kg) or by the selective
5-HT2 antagonist,
ketanserin (0.3 mg/kg).
1-(1-Naphthyl)piperazine also antagonized the decreases in responding produced by
quipazine (0.1-5.6 mg/kg), another agonist with predominant 5-HT2 actions.
1-(m-Chlorophenyl)piperazine (mCPP, 0.1-3.0 mg/kg) and
1-(m-trifluoromethylphenyl)piperazine (
TFMPP, 0.1-3.0 mg/kg), both thought to act primarily at 5-HT1 sites, also decreased responding and this effect was blocked by
methysergide and by 1-NP, but not by
ketanserin. The effects of 1-NP (0.3-5.6 mg/kg) given alone were not like those of mCPP or
TFMPP.
1-(1-Naphthyl)piperazine produced moderate increases in responding under
shock-avoidance schedules, whereas only decreases in responding were seen after mCPP and
TFMPP.(ABSTRACT TRUNCATED AT 250 WORDS)