Proceedings of The Physiological Society
University of Leeds (2002) J Physiol 544P, S017
Changes in the noradrenergic innervation of lumbosacral spinal cord following systemically administered DSP-4 have no effect on micturition pattern in the male rat
Richard N. Ranson, Katherine A. Gaunt, Robert M. Santer and Alan H.D. Watson
Cardiff School of Biosciences, Cardiff University, Biomedical Sciences Building, Cardiff CF10 3US, UK
Aged (24 month) male rats exhibit different in vivo micturition patterns to those of young adult (3 month) animals. In young rats, micturition episodes are smaller and more frequent during the night than during the day. In aged rats the pattern seen during the day continues at night and the volume of urine released over 24 h is greatly increased. These changes could be due to previously observed degeneration of long descending projections to spinal cord regions involved in the control of micturition (Santer et al. 2002). Since a proportion of these descending inputs are monoaminergic we used the neurotoxin DSP-4 (N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine) to deplete noradrenergic projections from the locus coeruleus in young rats to see whether this would result in the emergence of the aged pattern of micturition. Prior to DSP-4 injections the rats were placed in a metabolic cage for 24 h and urine samples collected on an electronic balance connected to a PC. Rats were then injected with Zimelidine (10 mg kg-1 I.P.) to protect 5-HT-containing neurones before the administration of DSP-4 (50 mg kg-1) either intraperitoneally (n = 4) or subcutaneously (n = 4). After a period of 7-10 days the micturition patterns of the rats were re-assessed on at least two separate occasions. Rats were then humanely killed by terminal anaesthesia ('Euthatal', sodium pentobarbitone, 200 mg kg-1) and perfused with 4 % paraformaldehyde. The effect of the DSP-4 on the distribution of catecholamines in the lumbosacral spinal cord was assessed using immunocytochemistry for tyrosine hydroxylase (TH, antibody TZ 1010, Affiniti Research Products Ltd). DSP-4 administration caused a marked reduction in TH immunopositive axons in both dorsal and ventral regions of the lumbosacral spinal cord, including regions containing motorneurones innervating the pelvic floor musculature. Despite this, statistical comparisons (Student's paired t test) of micturition data before and after DSP-4 treatment revealed no significant change. The maintenance of in vivo micturition characteristics in post-DSP-4 lesion rats may, however, reflect the fact that labelling within lumbosacral autonomic regions was generally preserved. Since lumbosacral monoaminergic labelling in autonomic regions in aged rats is known to decline, these findings suggest that DSP-4 lesions are not a good model for studying normal patterns of micturition during ageing.
This work was supported by SAGE grant (72/SAG 00911) from BBSRC.
All procedures accord with current UK legislation.
Where applicable, experiments conform with Society ethical requirements