Disruption of GABAergic tone in the dorsomedial hypothalamus attenuates responses in a subset of serotonergic neurons in the dorsal raphe nucleus following lactate-induced panic

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Abstract

Panic patients are vulnerable to induction of panic attacks by sub-threshold interoceptive stimuli such as intravenous (i.v.) sodium lactate infusions. Facilitation of serotonergic signaling with selective serotonin reuptake inhibitors can suppress anxiety and panic-like responses, but the mechanisms involved are not clearly defined. We investigated the effects of i.v. 0.5 M sodium lactate or saline, in control and panic-prone rats on c-Fos expression in serotonergic neurons within subdivisions of the midbrain/pontine raphe nuclei. Rats were chronically infused with either the GABA synthesis inhibitor l-allylglycine into the dorsomedial hypo thalamus to make them panic-prone, or the enantiomer d-allylglycine (d-AG) in controls. Lactate increased c-Fos expression in serotonergic neurons located in the ventrolateral part of the dorsal raphe nucleus (DRVL) and ventrolateral periaqueductal gray (VLPAG) of control, but not panic-prone, rats. The distribution of lactate-sensitive serotonergic neurons in d-AG-treated rats is virtually identical to previously defined pre-sympathomotor serotonergic neurons with multisynaptic projections to peripheral organs mediating 'fight-or-flight'- related autonomic and motor responses. We hypothesized that serotonergic neurons within the DRVL/VLPAG region represent a 'sympathomotor control system' that normally limits autonomic/behavioral responses to innocuous interoceptive and exteroceptive stimuli, and that dysfunction of this serotonergic system contributes to an anxiety-like state and increases vulnerability to panic in animals and humans.

Original languageEnglish (US)
Pages (from-to)642-652
Number of pages11
JournalJournal of Psychopharmacology
Volume22
Issue number6
DOIs
StatePublished - Aug 1 2008

Keywords

  • 5-HT
  • Anxiety
  • Autonomic
  • c-Fos
  • Panic
  • Periaqueductal gray
  • Raphe
  • Serotonin
  • Sympathetic

ASJC Scopus subject areas

  • Pharmacology
  • Psychiatry and Mental health
  • Neuroscience(all)

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