Effects of localized low-temperature pulses on the cockroach circadian pacemaker

Publisher Website
Google Scholar
Abstract
The hypothesis that the circadian pacemaker that controls the activity rhythm in the cockroach, L. maderae, is composed of mutually coupled optic lobe oscillators was investigated using localized low-temperature pulses. Following section of 1 optic tract cooling the intact optic lobe for 6 h (7.5.degree. C) beginning at activity onset consistently caused a phase delay of several hours. Cooling the neurally isolated lobe had little or no effect. The low-temperature phase probably 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 1 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 also reduced the delay caused by a low-temperature pulse. The cockroach circadian pacemaker is probably composed of 2 mutually coupled optic lobe oscillators.