Age-Related Features of Reactive Catecholamine Shifts in the Spinal Cord in Acute Somatic Pain: Experimental Study

Abstract

Objective: to study the age-related features of an adrenergic response of the central nervous system to acute somatic pain (ASP).

Subjects and methods: The spinal cord (SC) levels of adrenaline (A), noradrenaline (NA), and dopamine (DA) were studied in albino male rats of five age groups: 1) neonatal (2—4-day) rats; 2) 17—18-day rats that began to see; 3) monthly rats; 4) sexually mature (3—4 month) ones; and 5) old ones aged over 2 years. ASP was reproduced by electrodermal stimulation of the rat tail; the levels of catecholamines (CA) were measured by spectrofluorimetric microassay.

Results. During postnatal ontogenesis, the rats were found to have a phase pattern of physiological changes in the spinal concentrations of CA: a decrease in their high neonatal levels (due to DA) by the time the animals began to see; their progressive increase by prepuberty (due to NA) and in sexually maturity (due to A and DA), and a reduction in all CA fractions in old rats. ASP was attended by a rise in the SC concentration of CA in the neonatal animals and by clearly-cut reactive shifts in all fractions in the old ones. With A and DA increases, the SC concentrations of NA halved in the rats that began to see and had ASP; the amount of CA remained unchanged as compared with the controls. In prepubertal and sexually mature male rats, there was a reduction in the spinal CA pool, but due to different components: to A and NA in 35-day rats and to A and DA in 3-month ones.

Conclusion. Age-related changes in the pattern of a spinal CA response in rats with ASP show a ontogenetic trend in the development of adrenal responsiveness from the immature generalized forms of an early postnatal period to the definitive differentiated economic reactions of the hypo-to-normergic type and then to the hyperergic destructive reactions of old age.