Meeting Abstract
Control of cardiac output is dependent on the hormonal and nervous control mechanisms throughout the cardiovascular system and most notably within the heart. From teleost fish to mammals there is a noticeable variation in the complexity of cardiac control with mammals considered to have the most complex cardiac control mechanisms. Cardiac innervation studies in snakes indicate that, although the atrial chambers have a similar innervation pattern to that of mammals, the ventricle does not contain the cholinergic nerves found in mammals such as bats. These studies however may not have had the capacity to stimulate the nerves within the ventricle enough to elicit a response. Twenty four hearts from the reptile Ctenophorus ornatus were dissected into atrial and ventricular chambers and suspended from a force displacement transducer and placed in an organ bath containing reptile saline solution. Nerves were characterised by electrically stimulating the nerves, mimicking the response using exogenously applied adrenaline and acetylcholine before using known receptor blockers to block the response during further stimulation. By stimulating the nerves in the ventricular chambers at supra-maximal frequencies an increased neural cholinergic and adrenergic response is shown. The results of this nerve characterisation indicate the capacity for a squamate to have both adrenergic and cholinergic nerves innervating all chambers of the heart showing a complexity of control unseen previously in reptiles. Preliminary studies into other squamate reptiles have indicated a capacity for this level of cardiac control.
