title: Anatomical evidence for segregated input from the upper cervical spinal cord to functionally distinct regions of the periaqueductal gray region of the cat.
abstract: In the cat, the caudal third of the midbrain periaqueductal gray region (PAG) mediates two distinct behavioral and cardiovascular patterns: (i) flight and hypertension from the lateral PAG and (ii) immobility and hypotension from the ventrolateral PAG. The afferent input from the upper cervical spinal cord (UCC) to these functionally distinct PAG regions was investigated using retrograde tracing techniques. The following results were obtained: (i) following tracer injections into the lateral PAG large numbers of labelled cells were found in lamina I and the lateral cervical nucleus; (ii) following tracer injections into the ventrolateral PAG large numbers of labelled cells were found in the ventral horn; (iii) both PAG regions received substantial projections from UCC cells in laminae IV and V, however, no double labelled cells were observed. Thus, functionally distinct regions of the caudal PAG are targeted by quite separate and discrete UCC neural populations. These anatomical differences likely reflect functionally distinct UCC afferent regulation of the functionally opposite PAG regions.
authors.affiliation: Department of Anatomy, University of Sydney, NSW, Australia.
authors.forename: K A
authors.initials: KA
authors.lastname: Keay
authors.forename: R
authors.initials: R
authors.lastname: Bandler
mesh_terms: D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D002415:Cats; D006651:Histocytochemistry; D006710:Homocysteine / Q000031:analogs & derivatives / Q000494:pharmacology; D008636:Mesencephalon / Q000033:anatomy & histology / Q000166:cytology / Q000502:physiology; D010487:Periaqueductal Gray / Q000033:anatomy & histology / Q000502:physiology*; D013116:Spinal Cord / Q000033:anatomy & histology / Q000502:physiology*
chemical_list: D006710:Homocysteine; C007956:homocysteic acid