RT Journal Article
SR Electronic
T1 Manipulation of the Tetrahydrocannabinol Side Chain Delineates Agonists, Partial Agonists, and Antagonists
JF Journal of Pharmacology and Experimental Therapeutics
JO J Pharmacol Exp Ther
FD American Society for Pharmacology and Experimental Therapeutics
SP 1065
OP 1079
VO 290
IS 3
A1 B. R. Martin
A1 R. Jefferson
A1 R. Winckler
A1 J. L. Wiley
A1 J. W. Huffman
A1 P. J. Crocker
A1 B. Saha
A1 R. K. Razdan
YR 1999
UL http://jpet.aspetjournals.org/content/290/3/1065.abstract
AB Structure-activity relation studies have established that the alkyl side chain in tetrahydrocannabinol (THC) plays a crucial role in the activation of the cannabinoid receptor. Unfortunately, the flexible nature of this side chain has hampered efforts to elucidate the precise nature of the interaction of THC with its receptors. Therefore, a series of analogs with structurally restrained side chains of varying length was synthesized and evaluated for pharmacological potency in mice and for receptor affinity. The introduction of cisdouble bonds inserted rigid angles, whereas triple bonds developed regions of planarity. Receptor affinity for the acetylenic and saturated side chains were the same, whereas double bond substitution increased affinity 10-fold. Moreover, the relationship between receptor affinity and potency was 10-fold less than that of Δ8-THC in the case of some acetylenic derivatives, whereas changing the triple bond to a double bond restored the potency/affinity ratio. Additionally, an acetylene at C2–C3 in the octyl and nonyl side chains favored antinociception by as much as 70-fold. Surprisingly, several high-affinity acetylenic derivatives, especially those with cyano substitutions at the terminus of the side chain, were partial agonists or were inactive. Some of these low-efficacy, high-affinity ligands elicited antagonistic activity. The finding that manipulations of the side chain produces high- affinity ligands with either antagonist, partial agonist, or full agonist effects reveals a critical structural feature for receptor activation. The American Society for Pharmacology and Experimental Therapeutics