The interaction between the effects of vagus nerve stimulation (VS) and sympathetic stimulation (SS) on intrinsic heart rate was studied in the novel innervated isolated rabbit heart preparation. The effects of background VS, at different frequencies--2 Hz (low), 5 Hz (medium), 7 Hz (high)--on the chronotropic effects of different frequencies of SS--2 Hz (low), 5 Hz (medium), 10 Hz (high)--were studied. The experiments were repeated in the reverse direction studying the effects of different levels of background SS on the chronotropic effects of different levels of VS. Background VS reduced the overall positive chronotropic effect of SS at steady state in a frequency dependent manner and the rate of increase in heart rate during low and medium SS (but not high SS) was slowed in the presence of background VS. These results suggest that pre- and postjunctional mechanisms may be involved in the sympatho-vagal interaction on heart rate. On the other hand, the chronotropic effect of VS was enhanced in the presence of background SS. Vagal stimulation appears to play a dominant role over sympathetic stimulation in chronotropic effects on the isolated heart. The innervated isolated heart preparation is a valuable model to study the complex mechanisms underlying the interaction between sympathetic and parasympathetic stimulation on cardiac function.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1113/expphysiol.2003.002654

Interaction between direct sympathetic and vagus nerve stimulation on heart rate in the isolated rabbit heart

A frontal-vagal network theory for Major Depressive Disorder: Implications for optimizing neuromodulation techniques.

CHAPTER 9 – The Cardiovascular System

Publisher Summary This chapter addresses anesthesia and analgesia of more commonly used unconventional species, including special physiologic considerations, structural peculiarities, and methods for anesthetic administration. Relatively few anesthetic agents have been used in invertebrates. More commonly, invertebrates such as Drosophila and Caenorhabditis are used to study molecular activity, mutagenicity, and fertility effects of inhalant anesthetics. Thus, indirectly, several inhalant agents have been shown to be safe and effective when administered to invertebrates. Unfortunately, many researchers conduct invasive and potentially painful studies on invertebrates using no anesthetic at all. Invertebrates possess functional nervous systems and pain perception analogous to that of vertebrates; therefore, invasive procedures performed without appropriate anesthesia should not be tolerated in any species. Opioid-like compounds have been described in many invertebrates, including butterflies, blowflies, cockroaches, earthworms, snails, and octopus. Based on research investigations carried out so far, it is reasonable to assume that most, if not all, invertebrates possess opioid receptors and pain processing similar to vertebrates; these creatures, therefore, should be provided with appropriate anesthetics and analgesics when subjected to painful procedures.

Anesthesia and Analgesia in Nontraditional Laboratory Animal Species

We have isolated and characterized five overlapping clones that encompass 3.2 kb and encode a part of the short subfragment 2, the hinge, and the light meromyosin regions of the myosin heavy chain rod as well as 143 bp of the 3′ untranslated portion of the mRNA. Northern blot analysis showed expression of this mRNA mainly in ventricular muscle of the adult chicken heart, with trace levels detected in the atrium. Transient expression was seen in skeletal muscle during development and in regenerating skeletal muscle following freeze injury. To our knowledge, this is the first report of an avian ventricular myosin heavy chain sequence. Phylogenetic analysis indicated that this isoform is a distant homolog of other ventricular and skeletal muscle myosin heavy chains and represents a distinct member of the multigene family of sarcomeric myosin heavy chains. The ventricular myosin heavy chain of the chicken is either paralogous to its counterpart in other vertebrates or has diverged at a significantly higher rate.

Structural and phylogenetic analysis of the chicken ventricular myosin heavy chain rod.

We determined the effects of vagus nerve stimulation on cardiac cycle length and on ventricular contraction and relaxation in 18 chickens anesthetized with pentobarbital. Right vagus stimulation at a constant frequency of 35 Hz prolonged cycle length by 190%, whereas left vagus stimulation at the same frequency increased cycle length by 136%. When one burst of stimuli was delivered to the right vagus nerve each cardiac cycle, but the timing of the stimuli was changed within the cardiac cycle, the response of the avian pacemaker cells varied substantially with the timing of the stimuli. Right and left vagus stimulation at a constant frequency of 20 Hz depressed ventricular contraction by 62 +/- 6 and 52 +/- 6%, respectively, and depressed ventricular relaxation by 56 +/- 7 and 53 +/- 7%, respectively. These results indicate that in the chicken the chronotropic effects of right vagus stimulation are greater than those of left vagus stimulation, whereas right and left vagus stimulation are approximately equipotent on ventricular contraction and relaxation.

M. N. Levy

Papers

Effects of vagus nerve on heart rate and ventricular contractility in chicken.