Vol. 92, Issue 1, 331-342, January 2002
Neural responses to intravenous serotonin revealed by
functional magnetic resonance imaging
Luke A.
Henderson1,2,
Pearl L.
Yu1,
Robert C.
Frysinger1,
Jean-Philippe
Galons3,
Richard
Bandler2, and
Ronald M.
Harper1
1 Department of Neurobiology, University of California at
Los Angeles, California 90095-1763; 2 Department of Anatomy and
Histology and Pain Management and Research Center, Royal North
Shore Hospital, University of Sydney, Sydney, New South Wales 2006, Australia; and 3 Department of Radiology, University of
Arizona, Tucson, Arizona 85724
We examined the sequence of neural
responses to the hypotension, bradycardia, and apnea evoked by
intravenous administration of 5-hydroxytryptamine
(serotonin). Functional magnetic resonance imaging signal
changes were assessed in nine isoflurane-anesthetized cats during
baseline and after a bolus intravenous low dose (10 µg/kg) or high
dose (20-30 µg/kg) of 5-hydroxytryptamine. In all cats,
high-dose challenges elicited rapid-onset, transient signal declines in
the intermediate portion of the solitary tract nucleus, caudal midline
and caudal and rostral ventrolateral medulla, and fastigial nucleus of
the cerebellum. Slightly delayed phasic declines appeared in the
dentate and interpositus nuclei and dorsolateral pons. Late-developing
responses also emerged in the solitary tract nucleus, parapyramidal
region, periaqueductal gray, spinal trigeminal nucleus, inferior
olivary nucleus, cerebellar vermis, and fastigial nucleus. Amygdala and
hypothalamic sites showed delayed and prolonged signal increases.
Intravenous serotonin infusion recruits cerebellar, amygdala, and
hypothalamic sites in addition to classic brain stem cardiopulmonary
areas and exhibits site-specific temporal patterns.
myocardial ischemia; Bezold-Jarisch reflex; bradycardia; apnea; hypotension
