Several pieces of evidence suggest that the
noradrenergic afferents in the medial preoptic
area produce sleep and hypothermia by acting
on α1
adrenergic receptors. On the other hand,
in a few studies monitoring body temperature
with a rectal probe, preoptic injection of the α1
adrenergic agonist methoxamine produced
contradictory changes in body temperature and
sleep-wakefulness. Such contradictions call for
the re-examination of methoxamine induced
body temperature changes using a better
technique like telemetric recording. In the
present study, we monitored body temperature
and sleep-wakefulness simultaneously after the
micro-injection of 0.5, 1, and 2 μmol
methoxamine, into the medial preoptic area of
adult male Wistar rats. Methoxamine injection
produced hypothermia but no major change in
sleep-wakefulness during the 3 hours after drug
injection, except for a short period (15 min) of
sleep after 120 min of injection. A short period
of wakefulness, coinciding with the maximum
fall in body temperature (30 min after injection)
occurred when methoxamine was administered
at higher doses. The results of this study indicate
that 1 adrenergic receptors participate in preoptically
mediated thermoregulatory measures
that reduce body temperature. Hypothermia
induced by methoxamine might have masked
the hypnogenic action of this drug.
