PT  - JOURNAL ARTICLE
AU  - M J Millan
AU  - F C Colpaert
TI  - 5-hydroxytryptamine (HT)1A receptors and the tail-flick response. III. Structurally diverse 5-HT1A partial agonists attenuate mu- but not kappa-opioid antinociception in mice and rats.
DP  - 1991 Mar 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 993--1001
VI  - 256
IP  - 3
4099  - http://jpet.aspetjournals.org/content/256/3/993.short
4100  - http://jpet.aspetjournals.org/content/256/3/993.full
SO  - J Pharmacol Exp Ther1991 Mar 01; 256
AB  - This study examined the effects of structurally diverse 5-hydroxytryptamine (HT)1A partial agonists upon opioid-induced antinociception against noxious heat and pressure stimuli in rats and mice. The pyrimidinylpiperazines, buspirone, ipsapirone and gepirone, the halogenated phenylpiperazine, LY 165, 163 [1-(2-(4-aminophenyl)ethyl-4-(3-trifluoromethylphenyl)-piperazine], the heterobicylic arylpiperazine, (+/-)-flexinoxan, and the benzodiaxane, MDL 728328-[(4-(1,4-benzodioxon-2-ylmethylamino)butyl-8-azasp iro-(4,5)-decane-7,9-dione], exerted little or no effect upon basal latencies. In both mice and rats, each dose-dependently attenuated the antinociceptive action of the mu-opioid, morphine, against heat and pressure. In their presence, the morphine dose-response curve was shifted in parallel to the right with no loss of maximal effect. In mice, Schild analysis of the action of ipsapirone and gepirone yielded slopes of close to -1. In contrast to the partial agonists, the buspirone metabolite, 1-pyrimidinylpiperazine, which lacks 5-HT1A affinity, and the putative 5-HT1A antagonists, methiothepin, spiperone, BMY 7378 [(8-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-8-azaspirol [4]-decane-7,9-dione) 2HCl] and alprenolol, did not reduce the action of morphine. In rats, the antagonistic effect of buspirone, gepirone and ipsapirone could be blocked by BMY 7378. The 5-HT1A partial agonists also antagonized the antinociception-induced by the mu-opioid, sufentanil, but were virtually inactive against the selective kappa-opioid agonists, U69,593 (5 alpha,7 alpha,8 beta-(+)-N-methyl-N-[7-(l-pyrrolidinyl)-1-oxaspirol-(4,5)-dec-8-yl ] benzene-acetamide) and U50,488H (trans-(dl)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]-benzenacetamide methane sulfonate hydrate.(ABSTRACT TRUNCATED AT 250 WORDS)