Jmh. Preuss et al., AGE AND REGION-DEPENDENT CONTRACTION TO ALPHA-ADRENOCEPTOR AGONISTS IN RAT AND GUINEA-PIG ISOLATED TRACHEA, British Journal of Pharmacology, 123(8), 1998, pp. 1541-1548
1 The influence of age and of region on alpha-adrenoceptor-mediated co
ntraction to (-)-adrenaline and (-)-noradrenaline was examined in rat
(4-136 weeks) and guinea-pig (2-156 weeks) isolated tracheal ring prep
arations with particular emphasis on the early (up to 12 weeks) matura
tion phase. 2 In rat tracheal rings, significant regional variation wa
s observed with respect to maximal (-)adrenaline-induced contraction,
such that the greatest activity was seen in ring preparations from the
laryngeal end of the trachea. Tracheal rings from the carinal end res
ponded very poorly or were unresponsive to (-)-adrenaline, depending o
n animal age. These regional differences were seen across the age rang
e. The potencies of (-)-adrenaline and (-)-noradrenaline remained unch
anged with respect to animal age, but the maximum contractile tension
that developed in response to these agonists increased with increasing
animal age in all regions of the trachea. 3 In guinea-pig isolated tr
acheal tissue, maximum contractile responses (E-max) to (-)-adrenaline
and (-)-noradrenaline remained unchanged with increasing animal age.
In addition, there was no evidence for a region-dependence in the resp
onsiveness of tracheal tissue to alpha-adrenoceptor-mediated contracti
on in this species. 4 In both guinea-pig and rat isolated tracheal tis
sue, alpha-adrenoceptor-mediated contraction appeared to involve the a
ctivation of alpha(1)-adrenoceptors.