Bullfrogs, Lithobathes catesbeianus, bearing a femoral artery cannula were held at 3 temperatures (10,20 and 30 degrees C) for 24 h. Changes in heart rate were recorded before and after injection of cholinergic and adrenergic antagonists. Normal heart rate doubled for each temperature increment. Adrenergic tone on the heart varied around 20% at all 3 temperatures but cholinergic tone increased from -5% to 10% between 10 and 30 degrees C. In contrast, cholinergic tone increased from 75% at 5 degrees C to 329% at 25 degrees C in Xenopus laevis. Injection of the neural tracer True Blue into the cervical vagus of the bullfrog revealed a single location for vagal preganglionic neurons (VPN) in the dorsal vagal motor nucleus (DVN), while Xenopus had 30% of its VPN in a ventro-lateral group outside the DVN. Broader comparative studies have suggested that differences in the extent of vagal tone may relate to the location of VPN in the brainstem and this may be the case in these amphibians. (C) 2012 Elsevier Ltd. All rights reserved.
|Number of pages||5|
|Journal||Journal of Thermal Biology|
|Publication status||Published - 1 Apr 2012|
- Vagal preganglionic neurons
- Heart rate
- Autonomic control