An HRP study of the brainstem afferents to the accessory abducens region and dorsolateral pons in rabbit: Implications for the conditioned nictitating membrane response

John Desmond, Marcy E. Rosenfield, John W. Moore

Research output: Contribution to journalArticle


Brain projections to the accessory abducens region and dorsolateral pons were investigated in rabbit using implants of crystalline horseradish peroxidase (HRP). Following implantation of HRP in the accessory abducens region (N = 3), labeled cells were observed in the sensory trigeminal nuclei and other regions implicated in the reflex pathway of the defensive nictitating membrane (NM) response. Neurons in the supratrigeminal zone were also labeled, as were portions of the contralateral red nucleus. Implantation of HRP into the dorsolateral pons (N = 5) revealed ipsilateral projections from deep-cerebellar nuclei in some cases. In addition, the parvocellular reticular formation displayed bilateral labeling of cells and an ipsilateral network of fibers and apparent terminations. Many cells of the contralateral supratrigeminal zone were labeled in these cases. Results were discussed in relation to lesioning and electrophysiological studies implicating the supratrigeminal region and other structures in the control of the classically conditioned NM response. Specifically, the possibility that supratrigeminal neurons are premotor elements responsible for the conditioned response is considered. Alternative hypotheses are discussed, including pathways by which cerebellar nuclei could control conditioned responding.

Original languageEnglish (US)
Pages (from-to)747-763
Number of pages17
JournalBrain Research Bulletin
Issue number6
Publication statusPublished - 1983
Externally publishedYes



  • Accessory abducens region
  • Brainstem
  • Cerebellar nuclei
  • Classical conditioning
  • Dorsolateral pons
  • HRP
  • Nictitating membrane response
  • Rabbit
  • Red Nucleus
  • Supratrigeminal region

ASJC Scopus subject areas

  • Neuroscience(all)

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