AJP - Regulatory, Integrative and Comparative Physiology, Vol 240, Issue 3 144-R150, Copyright © 1981 by American Physiological Society
Effects of localized low-temperature pulses on the cockroach circadian pacemaker
T. L. Page
The hypothesis that the circadian pacemaker that controls the activity
rhythm in the cockroach, Leucophaea maderae, is composed of mutually
coupled optic lobe oscillators was investigated using localized
low-temperature pulses. Following section of one optic tract cooling the
intact optic lobe for 6 h (7.5 degrees C) beginning at activity onset
consistently caused a phase delay of several hours. Cooling the neurally
isolated lobe had little or no effect. The results suggested the
low-temperature phase delays the rhythm via a phase shift in an oscillator
in the optic lobe. To determine if optic lobe oscillators were coupled,
low-temperature pulses were given to one optic lobe of intact animals. If
the treated lobe was isolated by optic tract section 4 days after the
pulse, the rhythm (driven by the untreated lobe) was delayed; but if the
tract was cut 0.5 h after the pulse the phase shift was prevented. The
interaction between the optic lobes in intact animals was also found to
reduce the delay caused by a low-temperature pulse. These results suggest
the cockroach circadian pacemaker is composed of two mutually coupled optic
lobe oscillators.
