Observational studies of Dopamine D2‐family agonists in squirrel monkeys

Abstract

Dopamine D2‐family (D2) agonists and antagonists produce dose‐related increases in, respectively, scratching and catalepsy‐associated behavior (CAB) in squirrel monkeys.The effects of D2 ligands on observable behavior were further compared in the present study. Results show that D2 full agonists [(+)‐PHNO, R(−)‐NPA, quinelorane, PD 128907 and 7‐OH‐DPAT] produced dose‐dependent increases in scratching, with effects that varied in magnitude among drugs [R(−)‐NPA ≈ (+)‐PHNO (>35% of session) > quinelorane ≈ PD 128907 ≈ 7‐OH‐DPAT (<25%)]. D2 partial or mixed‐action agonists [terguride (TER), preclamol (PREC), talipexole (TAL), roxindole (ROX), aripiprazole (ARIP)] did not significantly increase scratching. Results also show that, like haloperidol (HAL), TAL, TER, ARIP and ROX produced dose‐related increases in CAB. HAL, TAL, and TER produced high levels of CAB (65–99% of session), whereas the mixed‐action D2 partial agonists ROX and ARIP produced lesser levels of CAB (<40%). The D2 full agonists (+)‐PHNO, 7‐OH‐DPAT and PD 128907 produced no evidence of CAB. Although the roles of D2 subtypes in agonist‐induced scratching or of intrinsic activity in CAB are not well understood, these behavioral endpoints serve as quantifiable measures of D2 receptor activation or blockade in primate species. (supported by NIH/NIDA RO1‐03774, RO1‐10566)