Effects of vagotomy and pharmacological blocking on heart rate of the toad Rhinella arenarum (Anura: Bufonidae) during forced submersion

CERVINO, C.O.; RODRÍGUEZ, ENRIQUE M.

CUADERNOS DE HERPETOLOGíA

ASOCIACIÓN HERPETOLÓGICA ARGENTINA

Lugar: San Miguel de Tucumán; Año: 2017

0326-551X

Toads of Rhinella (=Bufo) arenarum were subjected to a condition of forced submersion during a 40-minute period, to deepen the understanding of the mechanisms involved in the control of both submersion and emersion. Animals previously submitted to a first control measurement series, were then injected with atropine or propranolol, or were vagotomized. In animals either injected with atropine or vagotomized, a higher heart rate (HR) than in the control group was observed, before, during and after the forced submersion. These animals were able to decrease HR, although in a lesser extent than controls, suggesting that other mechanisms in addition to vagal activity are also producing and maintaining bradycardia during the submersion period. In those animals injected with propranolol (a β-adrenergic blocker), a HR lower than that of controls were observed only at the beginning of the submersion and during the emersion phase. The low HR caused by propranolol during emersion with buccal pumping shows the importance of the sympathetic system in increasing HR during emersion.