Sp. Mendoza et Wa. Mason, AUTONOMIC BALANCE IN SAIMIRI-SCIUREUS AND CALLICEBUS MOLOCH - RELATION TO LIFE-STYLE, Folia primatologica, 68(3-5), 1997, pp. 307-318
Previous research has shown heart rate to be substantially higher in s
quirrel monkeys (Saimiri sciureus) than titi monkeys (Callicebus moloc
h). In order to evaluate whether species differences in heart rate can
be accounted for by contrasting patterns of autonomic activity, heart
rate in response to novel test conditions was compared using standard
pharmacological agents that selectively block the sympathetic (propra
nolol) or parasympathetic (atropine) components of the autonomic nervo
us system, Squirrel monkeys were found to exhibit greater sympathetic
response to novelty than titi monkeys, In contrast, sympathetic activi
ty in titi monkeys, but not squirrel monkeys, was quickly counteracted
by a strong parasympathetic response, Intrinsic heart rates, estimate
d by blocking both parasympathetic and sympathetic input to the heart,
were within the ranges of values predicted by body weight. Heart rate
for titi monkeys stabilizes at intrinsic heart rate, whereas heart ra
te for squirrel monkeys is maintained well above intrinsic heart rate
in a novel environment, The contrast between species in autonomic bala
nce is consistent with and probably contributes to each species charac
teristic mode of interacting: with their social and non-social environ
ment.