The present study investigated the involvement of 5-hydroxytryptamine(1A) (5-HT(1A)) receptors in
Delta(9)-tetrahydrocannabinol (
THC)-induced
catalepsy-like immobilization in mice.
THC (10 mg/kg, i.p.) induced
catalepsy-like immobilization but had no effect on motor coordination in the rota-rod test. The selective
cannabinoid CB(1) receptor antagonist
rimonabant (3 mg/kg, i.p.) completely antagonized
THC-induced
catalepsy-like immobilization. The 5-HT(1A)/5-HT(7) receptor agonist 8-hydroxy-2-(di-n-propylamino)
tetralin (8-
OH-DPAT; 0.3 and 1 mg/kg, i.p.) and
5-HT(1A) receptor partial agonist
buspirone (0.06 and 0.1 mg/kg, i.p.) inhibited this
THC-induced
catalepsy-like immobilization. Moreover, the selective
5-HT(1A) receptor antagonist N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl) cyclohezane carboxamide dihydrochloride (WAY100635; 0.3 or 1 mg/kg, i.p.) reversed the inhibition of
THC-induced
catalepsy-like immobilization by
8-OH-DPAT (1 mg/kg) or
buspirone (0.06 mg/kg). In contrast, the selective 5-HT(7) receptor antagonist (R)-3-[2-[2-(4-methylpiperidin-1-yl)ethyl]
pyrrolidine-1-sulfonyl]
phenol hydrochloride (SB269970) had no effect on this inhibitory effect of
8-OH-DPAT. On the other hand, WAY100635 (0.3 and 1 mg/kg, i.p.) enhanced the
catalepsy-like immobilization induced by
THC (6 mg/kg, i.p.). These findings suggest that the 5-HT(1A) receptors are involved in
THC-induced
catalepsy-like immobilization.