Afferents to the central nucleus of the amygdala and functional subdivisions of the periaqueductal gray: Neuroanatomical substrates for affective behavior

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Abstract

Evidence suggests the periaqueductal gray (PAG) is involved in the integration of behavioral and autonomic components of affective behavior. Our laboratory has shown that electrical stimulation of the ventrolateral periaqueductal gray (vl PAG) versus the dorsolateral periaqueductal gray (dl PAG), in the rabbit, elicits two distinct behavioral/cardiorespiratory response patterns. Furthermore, evidence suggests that the amygdaloid central nucleus (ACe) may influence cardiovascular activity during emotional states. The purpose of this study was to delineate the topography and determine the origin of forebrain projections to the PAG and the ACe, as well as commonalties and differences in the pattern of afferents. Examination of common afferents may lend insights into their function as components of a forebrain system regulating autonomic activity during emotional states. Separate retrograde tracers were injected into functional subdivisions of the PAG and the ACe in rabbits. PAG injections led to neuronal labeling in numerous cortical regions including the ipsilateral medial prefrontal and insular cortices. Additionally, bilateral labeling was observed in several hypothalamic nuclei including the paraventricular nucleus, the dorsomedial nucleus and the ventromedial nucleus as well as the region lateral to the descending column of the fornix. Sparse labeling was also seen in various basal forebrain regions, thalamic nuclei and amygdaloid nuclei. Many of these regions were also labeled following injections in the ACe. Although double-labeled cells were never observed, afferents to the ACe were often proximal to PAG afferents. Implications of these findings are discussed in terms of two functionally distinct behavioral/cardiovascular response patterns.

Original languageEnglish (US)
Pages (from-to)157-173
Number of pages17
JournalBrain Research
Volume887
Issue number1
DOIs
StatePublished - Dec 22 2000

Keywords

  • Central nucleus of the amygdala
  • Emotional stress
  • Hypothalamus
  • Medial prefrontal cortex
  • Neuroanatomical tracer
  • Periaqueductal gray

ASJC Scopus subject areas

  • Neuroscience(all)

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