SENSORIMOTOR-CORRELATED DISCHARGE RECORDED FROM ENSEMBLES OF CEREBELLAR
PURKINJE CELLS VARIES ACROSS THE ESTROUS CYCLE OF THE RAT.
Smith, Sheryl S.
Dept. of Anatomy, Inst. of Neuroscience, Hahnemann University, Broad and
Vine, Philadelphia, PA 19102-1192, U.S.A., phone: 215-762-4407, fax: 215-762-
1982.
APStracts 2:0107N, 1995.
SUMMARY AND CONCLUSIONS
In the present study, locomotor-correlated activity of cerebellar Purkinje
cells, recorded using arrays of microwires chronically implanted in adult
female rats, was examined across estrous cycle- associated fluctuations in
endogenous sex steroids. Ongoing studies from this laboratory have shown that
systemic and local administration of the sex steroid 17 <F128>b<F255>-
estradiol (E 2 ) augments excitatory responses of cerebellar Purkinje cells to
iontophoretically applied glutamate, recorded in vivo from anesthetized female
rats. In addition, this steroid potentiated discharge correlated with limb
movement. For the present study, extracellular single unit activity was
recorded from as many as 5-11 Purkinje cells simultaneously during treadmill
locomotion paradigms. Motor modulation of activity was recorded across 3-5
consecutive estrous cycles from behaviorally identified cohorts of neurons to
test the hypothesis that fluctuations in endogenous sex steroids alter motor
modulation of Purkinje cell discharge. 1. Locomotor-associated discharge
correlated with treadmill locomotion was increased by a mean 47% on proestrus,
when E 2 levels are elevated, relative to diestrus 1. These changes in
discharge rate during treadmill locomotion were of significantly greater
magnitude than corresponding cyclic alterations in discharge during stationary
periods. 2. Correlations with the circadian cycle were also significant, as
peak levels of locomotor-associated discharge on the night of behavioral
estrus, following elevations in circulating E 2 , were on average 67% greater
than corresponding discharge recorded during the light (proestrus). 3.
Alterations in the step cycle were also observed across the estrous cycle:
Significant decreases in the duration of the flexion phase (by 265 msecs,
P<<0.05) were noted on estrus compared to diestrus. 4. When recorded on
estrus, Purkinje cell discharge correlated with the stance or flexion phase of
the step cycle was greater in magnitude and preceded the event by an average
of 130 msec, compared with values determined on diestrus. 5. On estrus,
responses of Purkinje neurons to iontophoretically applied quisqualate were
enhanced four-fold after administration of exogenous E 2 , assessed in
urethane- anesthetized female rats. 6. In addition, systemic administration of
E 2 (30 ngs, i.v.) potentiated responses of cerebellar Purkinje cells to
electrical stimulation of the forepaw by an average of 150%, recorded in
anesthetized female rats. 7. These results are consistent with the hypothesis
that elevations in circulating E 2 are associated with enhanced discharge of
cerebellar Purkinje cells in response to pharmacological or electrical stimuli
or associated with locomotor behavior.
Received 6 July 1994; accepted in final form 31 March 1995.
APS Manuscript Number J401-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 1 May 1995.