Nervous control of the spleen in the red-blooded antarctic fish,
pagothenia borchgrevinki.
Nilsson, Stefan, Malcolm E. Forster, William Davison, and Michael
Axelsson.
Department of Zoology, University of Canterbury, Private Bag 4800,
Christchurch, New Zealand
APStracts 2:0298R, 1995.
The mechanisms of splenic control in the Antarctic fish, Pagothenia
borchgrevinki were investigated using isolated spleen and mesenteric
artery strips in vitro and perfused spleen preparations in situ.
Spleno-somatic index (SSI) [100x(spleen weight/body weight)] and
haematocrit were determined in animals treated with atropine and
phentolamine. Atropine injection increased the SSI from 0.60+/-0.06
to 0.89+/-0.04, while phentolamine decreased SSI down to 0.45+/-0.03.
In atropine-injected fish, haematocrit was 18.6+/-1.4 before, and
6.6+/-0.8% 3 h after injection. Electrical stimulation of the splenic
nerves produced biphasic flow responses. In 11 out of the 12 tested
preparations, atropine (3x10-7-10-6 M) abolished the response,
suggesting a major cholinergic component in the splenic innervation.
Isolated spleen strip preparations contracted in response to
carbachol, a response that was antagonized by atropine. The response
to acetylcholine was markedly enhanced by the specific cholinesterase
inhibitor BW 284 c51. Catecholamine effects were somewhat irregular,
and maximal contraction force with epinephrine and norepinephrine
were 41 and 56%, respectively, of the carbachol response. The results
suggest a mainly, if not solely, cholinergic autonomic control of the
borch spleen, and a major function of the cholinergic innervation in
the control of haematocrit in this species.
Received 30 May 1995; accepted in final form 19 October 1995.
APS Manuscript Number R321-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 14 November 95