Experiments were performed on adult rainbow trout (Oncorhynchus mykiss) in vivo using chronically cannulated fish and in situ using a perfused posterior cardinal vein preparation (i) to characterise the desensitisation of chromaffin cell nicotinic receptors and (ii) to assess the ability of fish to secrete catecholamines during acute hypoxia with or without functional nicotinic receptors. Intra-arterial injection of nicotine (6.0×10(−)(7)mol kg(−)(1)) caused a rapid increase in plasma adrenaline and noradrenaline levels; the magnitude of this response was unaffected by an injection of nicotine given 60 min earlier. Evidence for nicotinic receptor desensitisation, however, was provided during continuous intravenous infusion of nicotine (1.3×10(−)(5)mol kg(−)(1)h(−)(1)) in which plasma catecholamine levels increased initially but then returned to baseline levels. To ensure that the decline in circulating catecholamine concentrations during continuous nicotine infusion was not related to changes in storage levels or altered rates of degradation/clearance, in situ posterior cardinal vein preparations were derived from fish previously experiencing 60 min of saline or nicotine infusion. Confirmation of nicotinic receptor desensitisation was provided by demonstrating that the preparations derived from nicotine-infused fish were unresponsive to nicotine (10(−)(5)mol l(−)(1)), yet remained responsive to angiotensin II (500 pmol kg(−)(1)). The in situ experiments demonstrated that desensitisation of the nicotinic receptor occurred within 5 min of receptor stimulation and that resensitisation was established 40 min later. The ability to elevate plasma catecholamine levels during acute hypoxia (40–45 mmHg; 5.3-6.0 kPa) was not impaired in fish experiencing nicotinic receptor desensitisation. Indeed, peak plasma adrenaline levels were significantly higher in the desensitised fish during hypoxia than in controls (263+/−86 versus 69+/−26 nmol l(−)(1); means +/− s.e.m., N=6-9). Thus, the results of the present study demonstrate that activation of preganglionic sympathetic cholinergic nerve fibres and the resultant stimulation of nicotinic receptors is not the sole mechanism for eliciting catecholamine secretion during hypoxia.
Desensitisation of chromaffin cell nicotinic receptors does not impede catecholamine secretion during acute hypoxia in rainbow trout (Oncorhynchus mykiss)
K.N. Lapner, C.J. Montpetit, S.F. Perry; Desensitisation of chromaffin cell nicotinic receptors does not impede catecholamine secretion during acute hypoxia in rainbow trout (Oncorhynchus mykiss). J Exp Biol 15 May 2000; 203 (10): 1589–1597. doi: https://doi.org/10.1242/jeb.203.10.1589
Download citation file:
The Forest of Biologists
We are excited to announce the launch of The Forest of Biologists, a new biodiversity initiative created with support from the Woodland Trust, aiming to counteract nature loss and safeguard some of the most critically endangered ecosystems for future generations. For every Research Article and Review/Commentary article that is published in JEB (and our sister journals Development, Journal of Cell Science, Disease Models & Mechanisms and Biology Open), a native tree is planted in a forest in the UK.
Celebrating 100 years of discovery
We are proud to be celebrating 100 years of discovery in Journal of Experimental Biology. Visit our centenary webpage to find out more about how we are marking this historic milestone.
Looking back on the first issue of JEB
Journal of Experimental Biology launched in 1923 as The British Journal of Experimental Biology. As we celebrate our centenary, we look back at that first issue and the zoologists publishing their work in the new journal.
In our new Conversation series JEB@100, JEB Editor-in-Chief Craig Franklin talks about the big outstanding questions in the field of physiological plasticity and why he thinks a sense of community is key to the journal's success. Find out more here.
Surface friction alters the agility of a small Australian marsupial
Matthew Eizenga and colleagues have discovered that Mexican fruit flies vanish in a blur in the eyes of predatory spiders when they wave their wings at the arachnids, buying the flies time to make their escape.
Propose new workshop for 2025
Do you have an idea for a Workshop? We are now accepting proposals for our 2025 Biologists Workshops programme. As the scientific organiser, your involvement will be focused on the science. We'll take care of all the logistics. In 2025 we'll continue our efforts to diversify our Workshop programme and will be reserving one of our Workshops for an application from a Global South (GS) country to host an event overseas.