Cardiovascular reflexes in conscious toads.
Methods used for implanting sensors and catheters in temporarily ether-anesthetized toads (Bufo paracnemis) are described. Following recovery it was found that distension of the pulmocutaneous arterial trunk and high frequency electrical stimulation of the laryngeal nerve of conscious toads induce an abrupt fall in arterial pressure accompanied or not by bradycardia or cardiac arrest. A brief suppression of throat movements may occur but this is not a constant finding. The response is blocked by atropine or methyl-homatropine and persists in animals with high spinal sectioning, thus indicating its cholinergic parasympathetic nature. However a certain amount of sympathetic inhibition is not ruled out. Perfusion of the artery with lobeline and electrical stimulation of the laryngeal nerve at low frequency (1/s) induces a rise in arterial pressure which is blocked by phentolamine. The hypertension is followed by enhancing of both throat oscillations and electromyographic discharges. The occurrence of chemoreceptors in the pulmocutaneous arterial wall in these animals is discussed. Blockage of the laryngeal nerve with lidocaine or perfusion of the pulmocutaneous arterial trunk with the same solution elicited a blood pressure rise, tachycardia and enhanced ventilatory movements. This was attributed to suppression of the baroreceptor tonus.
D000818:Animals; D001794:Blood Pressure; D002025:Bufonidae; D004558:Electric Stimulation; D006339:Heart Rate; D007823:Laryngeal Nerves / Q000502:physiology; D008465:Mechanoreceptors / Q000502:physiology; D011651:Pulmonary Artery / Q000294:innervation; D012018:Reflex / Q000502:physiology*; D012867:Skin / Q000098:blood supply; D013116:Spinal Cord / Q000502:physiology; D014630:Vagus Nerve / Q000502:physiology*