The rat: a laboratory model for studies of the diving response

Abstract

Underwater submersion in mammals induces apnea, parasympathetically mediated bradycardia, and sympathetically mediated peripheral vasoconstriction. These effects are collectively termed the diving response, potentially the most powerful autonomic reflex known. Although these physiological responses are directed by neurons in the brain, study of neural control of the diving response has been hampered since 1) it is difficult to study the brains of animals while they are underwater, 2) feral marine mammals are usually large and have brains of variable size, and 3) there are but few references on the brains of naturally diving species. Similar responses are elicited in anesthetized rodents after stimulation of their nasal mucosa, but this nasopharyngeal reflex has not been compared directly with natural diving behavior in the rat. In the present study, we compared hemodynamic responses elicited in awake rats during volitional underwater submersion with those of rats swimming on the water's surface, rats involuntarily submerged, and rats either anesthetized or decerebrate and stimulated nasally with ammonia vapors. We show that the hemodynamic changes to voluntary diving in the rat are similar to those of naturally diving marine mammals. We also show that the responses of voluntary diving rats are 1) significantly different from those seen during swimming, 2) generally similar to those elicited in trained rats involuntarily "dunked" underwater, and 3) generally different from those seen from dunking naive rats underwater. Nasal stimulation of anesthetized rats differed most from the hemodynamic variables of rats trained to dive voluntarily. We propose that the rat trained to dive underwater is an excellent laboratory model to study neural control of the mammalian diving response, and also suggest that some investigations may be done with nasal stimulation of decerebrate preparations to decipher such control.

Seizure-associated central apnea in a rat model: Evidence for resetting the respiratory rhythm and activation of the diving reflex

“…The mammalian diving response is an extremely powerful reflex response to nasopharyngeal stimulation with water that results in apnea, bradycardia, and increased systemic blood pressure (Golanov et al, 2016; Gooden, 1994; Panneton, 2013; Panneton et al, 2010; Panneton et al, 2012). The coordinated respiratory, parasympathetic, and sympathetic responses highlight the integration of these systems.…”

New Approaches to Quantifying Sympathetic Nerve Activity

“…The lower panels show raw renal SNA, integrated renal SNA, and arterial blood pressure signals obtained from one rabbit with 2K1C hypertension [48,59]. It has recently been shown that the diving reflex in conscious rats and nasal stimulation with ammonia in anesthetized rats evoke bradycardia and apnea similar to the response in rabbits [60]. Although SNA was not directly measured, it is likely that the large increase in SNA is not unique to rabbits, so this method may be applicable to other species.…”

Training Rats to Voluntarily Dive Underwater: Investigations of the Mammalian Diving Response

“…An adage in comparative physiology, the Krogh principle 7 , is that for every research question there is some animal of choice on which the problem can be most conveniently studied. A most appropriate animal for studying the central aspects of the diving response is the rat 6,8 . In large part this is due to the fact that the brains of rats have been very well characterized, both anatomically and functionally, and many rat brain atlases are available 6 .…”

“…Investigating the central nervous integration of the cardiorespiratory responses to diving is important for a number of reasons 6,8,28 . The diving response enables animals, including humans, to remain submerged underwater without breathing for extended periods of time.…”