The aim of the study was to discern the role of the endogenous serotonin
system in opiate withdrawal, in both somatic and emotional
aspects, along with its possible interaction with clonidine effects. To this
end, a protocol based on near complete lesion of main serotonergic
brain centers was carried out, and serotonin neurotransmission was
also blocked by 8-hydroxy-dipropylaminotetraline (8-OHDPAT), 5-
HT1A receptor agonist. The findings revealed that the serotonin system
is not involved in somatic abstinence, and clonidine efficacy was not
affected after serotonin depletion. The findings also revealed that the
serotonin system is not involved in the emotional aspect of opiate abstinence,
as measured through conditioned place aversion in rats. However,
antiaversive clonidine efficacy was enhanced near 10 times following
serotonin depletion. Moreover, 8-OHDPAT treatment induced
similar effects on antiaversive clonidine efficacy to those found after
serotonin depletion. Hence, the combined use of 5-HT1A receptor agonists
and clonidine could be of value for treatment of opiate withdrawal
syndrome.