G. Bollweg et Sb. Sparber, RELATIONSHIPS BETWEEN MIDEMBRYONIC 5-HT2 AGONIST AND OR ANTAGONIST EXPOSURE AND DETOUR LEARNING BY CHICKENS/, Pharmacology, biochemistry and behavior, 60(1), 1998, pp. 47-53
The importance of serotonin (5-HT) as both a transmitter and a regulat
ory signal during development of many species is well established. The
availability of 5-HT receptor subtype agonists and antagonists will e
nable pharmacological dissection of the importance of one or more of t
he 5-HT receptors for their involvement in the mediation of developmen
tal insults by drugs that are less selective but include actions upon
serotonergic function. Such insults include exposure to cocaine or opi
ate withdrawal, both of which are blocked or attenuated by 5-HT2 antag
onists. The 5-HT2 receptor agonist dimethoxyiodophenylaminopropane (DO
I),like cocaine, causes vasoconstriction during embryogenesis, herniat
ed umbilici in hatchlings, and altered detour learning by young chicke
ns after injection into eggs at late stages of embryogenesis. The 5-HT
2 antagonist ritanserin (RIT) blocks or significantly attenuates these
effects. This study describes an effect of DOI on posthatch detour le
arning when injected earlier during embryogenesis (i.e., on embryonic
day 12, E12) which is opposite its effect when injected later (i.e., o
n E15). Both effects are blocked by an inactive dose of RIT (0.3 mg/kg
egg) and by a higher dose of RIT (0.9 mg/kg egg), which itself retard
s posthatch detour learning following E12 injection. Thus, excessive s
timulation or blockade of 5-HT2 receptors around midembryogenesis can
cause a similar behavioral teratogenic outcome. The data are discussed
in relation to the likelihood that potential use of 5-HT2 antagonists
for treating pregnant women and their fetuses who are not at risk is
nil. (C) 1998 Elsevier Science Inc.