Circadian Activity Rhythm in the CNS and its Control
K. P. RAO
Abstract
The scorpion, H.julvipes and the cockroach, P. americana exhibit a circadian
rhythm in their locomotory activity. A parallel rhythm is recordable in the spontaneous electrical activity of the VNC in both. Blood or extracts of the S. 0
ganglion or the CTNM taken at different times of the day and applied to the VNC
in vitro also exhibit a rhythm in their ability to enhance or lower the nervous
activity. In the scorpion there is also a cyclic reversal of the sign of the photokinetic response. It is suggested that the activity rhythm in the CNS is regulated
through the interaction of the non-specific sensory input and the excitability state
of the CNS as conditioned by the "neurohormone-like factors".
Several organisms are known to exhibit rhythms of a circadian nature
in their locomotor activity and other kinds of physiological activities. A
great amount of information is available on the time course and phase
relations of such rhythms [1]. However very little is known about the
internal regulating mechanisms related to the nervous system which play
a role in modulating the motor activity into a circadian rhythm.
We have been studying the physiology and ecology of the scorpion,
Heterometrus fit/vipes for the past several years in our laboratory [5] and it
has been demostrated that this scorpion exhibits a diurnal rhythm in its
locomotor activity when kept under natural conditions of light and dark,
with a period of high activity between 5 p.m. and 10 p.m., with the peak
around 8 p.m. When kept in continuous dar kess the rhythm persists with
a circadian periodicity.
Several investigators have shown a similar diurnal rhythm to occur in
the locomotor activity of the cockroach, Periplaneta americana [1, 7]. It
persists for several weeks in darkness. But a decapitated cockroach becomes arrhythmic.
Since the locomotor activity depends on the motor output from the
CNS, we examined the "spontaneous" activity in the VNC of the scorpion,
isolated at different times of the day, and this revealed that the level of such
activity varied with the time of the day, maximum activity being noticed
between about 4 p.m. and 11 p.m. After about 11 p.m. the activity in the
VNC decreased and reached extremely low levels in the early hours of
the morning. The analysis of the spike heights and frequencies indicated
that the increase was not merely due to increased frequency of the same
K. P. RAO
Abstract
The scorpion, H.julvipes and the cockroach, P. americana exhibit a circadian
rhythm in their locomotory activity. A parallel rhythm is recordable in the spontaneous electrical activity of the VNC in both. Blood or extracts of the S. 0
ganglion or the CTNM taken at different times of the day and applied to the VNC
in vitro also exhibit a rhythm in their ability to enhance or lower the nervous
activity. In the scorpion there is also a cyclic reversal of the sign of the photokinetic response. It is suggested that the activity rhythm in the CNS is regulated
through the interaction of the non-specific sensory input and the excitability state
of the CNS as conditioned by the "neurohormone-like factors".
Several organisms are known to exhibit rhythms of a circadian nature
in their locomotor activity and other kinds of physiological activities. A
great amount of information is available on the time course and phase
relations of such rhythms [1]. However very little is known about the
internal regulating mechanisms related to the nervous system which play
a role in modulating the motor activity into a circadian rhythm.
We have been studying the physiology and ecology of the scorpion,
Heterometrus fit/vipes for the past several years in our laboratory [5] and it
has been demostrated that this scorpion exhibits a diurnal rhythm in its
locomotor activity when kept under natural conditions of light and dark,
with a period of high activity between 5 p.m. and 10 p.m., with the peak
around 8 p.m. When kept in continuous dar kess the rhythm persists with
a circadian periodicity.
Several investigators have shown a similar diurnal rhythm to occur in
the locomotor activity of the cockroach, Periplaneta americana [1, 7]. It
persists for several weeks in darkness. But a decapitated cockroach becomes arrhythmic.
Since the locomotor activity depends on the motor output from the
CNS, we examined the "spontaneous" activity in the VNC of the scorpion,
isolated at different times of the day, and this revealed that the level of such
activity varied with the time of the day, maximum activity being noticed
between about 4 p.m. and 11 p.m. After about 11 p.m. the activity in the
VNC decreased and reached extremely low levels in the early hours of
the morning. The analysis of the spike heights and frequencies indicated
that the increase was not merely due to increased frequency of the same