title: Fall in density, but not number of myenteric neurons and circular muscle nerve fibres in guinea-pig colon with ageing.
abstract: In guinea-pig ileum, ageing has been associated with a decrease in enteric neurons. This study examined guinea-pig colon and measured changes in gut dimensions, neuron size, density and ganglionic area. Changes in motor nerve fibres in the circular muscle were also measured. Myenteric neurons in whole-mount preparations of mid-colon from 2-week, 6-month, and 2-year-old guinea-pigs were labelled immunohistochemically with the neuronal marker human neuronal protein HuC/HuD, and numbers of neurons mm(-2), neuronal size, ganglionic area mm(-2), gut length, circumference and muscle thickness were measured. Corrected numbers of neurons mm(-2) and ganglionic area mm(-2) accounting for growth of the colon were calculated. Additionally, nerve fibres in circular muscle cross-sections were labelled with antibodies against nitric oxide synthase (NOS) and substance P (SP) and the density of nerve fibres in circular muscle was measured. The numbers of neurons mm(-2) decreased by 56% (from 2 weeks to 2 years) with no change in neuron size. Total neuron numbers decreased by 19% (P = 0.14) when adjusted for changes in length and circumference with age. The percentage area of NOS- and SP-immunoreactive (IR) nerve fibres in the circular muscle decreased (P < 0.001), but the total area of NOS and SP-IR nerve fibres increased (P < 0.01) due to an age-related increase in muscle thickness. The density of myenteric neurons in guinea-pig mid-colon halved from 2 weeks to 2 years, but when the increase in colon dimensions was considered, the number of neurons decreased by only 19%. The percentage area of motor nerve fibres in the circular muscle decreased with no change in total volume of nerve fibres.
authors.affiliation: F.D. Stephens Surgical Research Laboratory, Murdoch Childrens Research Institute, Melbourne, Australia.
authors.forename: C J
authors.initials: CJ
authors.lastname: Peck
authors.forename: S D
authors.initials: SD
authors.lastname: Samsuria
authors.forename: A M
authors.initials: AM
authors.lastname: Harrington
authors.forename: S K
authors.initials: SK
authors.lastname: King
authors.forename: J M
authors.initials: JM
authors.lastname: Hutson
authors.forename: B R
authors.initials: BR
authors.lastname: Southwell
mesh_terms: D000375:Aging / Q000502:physiology*; D000818:Animals; D002452:Cell Count; D003106:Colon / Q000033:anatomy & histology / Q000254:growth & development* / Q000294:innervation*; D017615:Enteric Nervous System / Q000166:cytology; D005724:Ganglia / Q000166:cytology / Q000502:physiology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D008856:Microscopy, Fluorescence; D009046:Motor Neurons / Q000502:physiology*; D009197:Myenteric Plexus / Q000033:anatomy & histology / Q000166:cytology*; D009412:Nerve Fibers / Q000502:physiology*; D016707:Tissue Fixation