Intracerebroventricular
administration of corticotropin-releasing factor
antagonist attenuates arousal response
accompanied by yawning behavior in
rats
Kita I, Kubota N, Yanagita S, Motoki C
Department of
Human Health Science, Tokyo Metropolitan
University Japan.
We have reported that an arousal response
accompanied by yawning behavior can be evoked by
electrical and chemical stimulation of the
hypothalamic paraventricular nucleus (PVN) in
rats, although the mechanism responsible for the
arousal response accompanied by yawning evoked
by PVN stimulation is still unknown. In the
present study, we examined the involvement of
corticotropin-releasing factor (CRF) in the
arousal response during yawning induced by
electrical stimulation of the PVN in
anesthetized, spontaneous breathing rats using
intracerebroventricular (icv) injection of
alpha-helical CRF, a CRF antagonist (4.2mug,
lateral ventricle). The electrocorticogram
(ECoG) was recorded to evaluate arousal
responses during yawning. Fast Fourier transform
was used to obtain the power spectrum in delta
(0.5-4Hz), theta (4-8Hz), alpha (8-13Hz), and
beta (13-20Hz) bands. We also recorded the
intercostal electromyogram as an index of
inspiratory activity and blood pressure (BP) as
an index of autonomic function to evaluate
yawning response. PVN stimulation induced
significant increases in relative powers of
theta, alpha, and beta bands, but not delta
band, concurrent with yawning events regardless
of icv injection, though the relative powers
after icv injection of alpha-helical CRF were
significantly lower than those after saline
injection. These findings suggest that CRF
neurons in the PVN are primarily responsible for
the arousal response accompanied by yawning
behavior.
-Kita I, Kubota N,
Yanagita S, Motoki C Intracerebroventricular
administration of corticotropin-releasing factor
antagonist attenuates arousal response
accompanied by yawning behavior in rats.
Neurosci.Letter 2008;433(3):205-208
-Kita I, Yoshida
Y, Nishino S. An activation of parvocellular
oxytocinergic neurons in the paraventricular
nucleus in oxytocin-induced yawning and penile
erection. Neurosci Res. 2006;54(4):269-275
-Kita I,
Sato-Suzuki et al.Yawning responses induced
by local hypoxia in the paraventricular nucleus
of the rat.Behavioural Brain Research
2000;117(1-2):119-126
-Kubota N, Amemiya
S, Motoki C, Otsuka T, Nishijima T, Kita I.
Corticotropin-releasing factor antagonist
reduces activation of noradrenalin and serotonin
neurons in the locus coeruleus and dorsal raphe
in the arousal response accompanied by yawning
behavior in rats. Neurosci Res.
2012;72(4):316-323
-Seki Y, Y
Nakatani, et al Light induces cortical
activation and yawning in rat Behav Brain Res
2003;140(1-2):65-73
-Seki Y,
Sato-Suzuki I, et al Yawning/cortical
activation induced by microinjection of
histamine into the paraventricular nucleus of
the rat. Behav Brain Res.
2002;134(1-2):75-82.
-Sato-Suzuki I,
Kita I, Oguri M, Arita H Stereotyped yawning
responses induced by electrical and chemical
stimulation of paraventricular nucleus of the
rat Journal of Neurophysiology,
1998;80(5)2765-2775
Yawning is known to be typically associated
with the induction of an arousal response. In
previous studies, we recorded the
electrocorticogram (ECoG) to evaluate arousal
responses during yawning evoked by several forms
of chemical stimulation of the paraventricular
nucleus (PVN) of the hypothalamus in
anesthetized, spontaneously breathing rats, and
found that an arousal shift in the ECoG,
represented by lower voltage and faster rhythm,
occurred prior to yawning behavior. However, the
mechanism responsible for the arousal response
accompanied by yawning evoked by PVN stimulation
is still unknown..I is widely believed that
activation of the descending oxytocinergic
system in the PVN is one of the most important
mechanisms responsible for yawning . The PVN
contains various neuropeptides besides oxytocin,
such as corticotropin-releasing factor (CRF),
vasopressin, and dynorphine. We recently found,
using c-Fos immunohistochemistry in rats, that
activation of not only oxytocin neurons but also
CRF neurons in the PVN is responsible for the
arousal/yawning response induced by PVN
stimulation. CRF neurons in the PVN are known to
play critical roles in arousal, autonomic, and
behavioral responses associated with various
stressors. Several studies have suggested that
stressful manipulations can modify the induction
of arousal/yawning responses. Taken together, it
is possible that CRF neurons in the PVN are
involved in the induction of the arousal
response accompanied by yawning. In the present
study, we examined the involvement of CRF in the
arousal response during yawning induced by
electrical stimulation of the PVN in
anesthetized, spontaneous breathing rats using
intracerebroventricular (icy) injection of a CRF
receptor antagonist.
Single icy injection of a-helical CRF did
not affect the responses of physiological
parameters, such as BP, HR and respiration,
during the control period before electrical
stimulation of the PVN. Electrical stimulation
of the PVN induced a stereotyped yawning
response in both pretreatment conditions, i.e.,
alter icy injection of a-helical CRF or saline
(data not shown). The response pattern was
characterized by an initial depressor phase
followed by a final yawning event (a single
large inspiratory effort), and was comparable to
that observed in our previous studies. As for
ECoG, during the control period before the PVN
stimulation, the ECoG of anesthetized rats was
characterized by large amplitude slow waves in
both pretreatment conditions. ECoG waves during
yawning induced by PVN stimulation shifted to
smaller amplitude faster waves in control rats
(saline, icy), whereas pretreatment with icy
injection of a-helical CRF tended to attenuate
its response.
The effects of a-helical CRF (icy) on the
relative power of each ECoG band before and
after electrical stimulation of the PVN are
presented. Two-way ANOVA revealed significant
interactions between stimulation and icy
injection for all bands [F(1,28)=1.61,
p<0.05 for delta; F(l,28)=39.62, p<O.Ol
for theta; F(l,28)=5.20, pzO.O5 for alpha;
F(1,28)= 17.96,p<0.01 for beta]. Single
icy injection of a-helical CRF did not affect
the relative power of any band during the
control period before electrical stimulation of
the PVN.
Although PVN stimulation induced significant
increases in relative powers of theta, alpha,
and beta bands compared with the control period
regardless of the solution used for icy
injection, the relative powers alter icy
injection of a-helical CRF were significantly
lower than alter saline. On the other hand, the
relative power of the delta band with
pretreatment with a-helical CRF was not
significantly altered by PVN stimulation
compared with the control period, although the
relative power of the delta band in control rats
(saline, icy) was significantly decreased by PVN
stimulation. These findings indicate that ECoG
waves shifted to faster rhythms, concurrent with
yawning events, and that ahelical CRF (icy)
could partially antagonize the shift to faster
rhythm accompanying yawning.
This is the first study to determine the
involvement of CRF in the arousal response
during yawning induced by PVN stimulation in
rats. CRF is known to play an important role as
the hypothalamic neurohormone that initiates
activation of the hypothalamic-pituitary-adrenal
axis (HPA axis) during stress [20,33].
In addition, CRF can serve in extrahypophyseal
brain regions as one of the neurotransmitters
most likely to be involved in mediating arousal
response as well as autonomic and behavioral
responses to various stressors. We have
previously reported that stress-like stimulation
such as local hypoxia in the PVN and light
stimulation induces not only the yawning
response but also an arousal shift in the ECoG.
These findings suggest the possibility that CRF
neurons in the PVN, which can be activated by
various stressors, mediate the arousal response
accompanying yawning behavior. The mechanism by
which activation of CRF neurons produces yawning
response is unclear, but nitric oxide (NO)
produced within CRF neurons may cause the
yawning response. Several studies have
demonstrated co-localization of NO synthase
(NOS) with CRF-producing parvocellular neurons
in the PVN. NO is a diffusible
neurotransmitter/neuromodulator and acts as a
paracrine agent. It is, thus, possible that
diffusible NO produced within CRF neurons
activates descending oxytocinergic system in the
PVN, which is one of the most important
mechanisms responsible for yawning, and its
actions on oxytocinergic neurons elicit yawning.
This possibility could be supported by previous
studies showing that NO could be involved in
induction of yawning via an activation of
oxytocinergic neurons projecting to the pons and
medulla oblongata.
Although the CRF-containing pathway involved
in the arousal response accompanied by yawning
evoked by PVN stimulation or stress is still
unknown, this arousal response may be mediated
by the widespread projections of neurons in the
brainstem reticular formation. A series of
animal studies has suggested that CRF serves as
an excitatory neurotransmitter in the locus
coeruleus (LC), one of the neuronal aggregates
within the brainstem reticular formation
respohsible for cortical activation. It has been
found that the LC, which is one of the major
sources of noradrenaline (NA) in the central
nervous system, receives CRF afferents from the
PVN, and projects to various brain areas
includingregions of cortex. Curtis et al. found
that activation of the LC neurons by CRP
administration into the LCincreases, cortical NA
release and ECoG activity, whereas local
microinfusion of a CRF antagonist directly into
the LC greatly decreases the magnitude of LC
activation produced by icy administration of
CRF. We recently demonstrated that PVN
stimulation significantly enhances c-Fos
expression in the LC as well as throughout the
cortex, together with increases in the
percentage of c-Fos positive CRF neurons in the
PVN and the frequency of yawning. It is thus
possible that activation of the noradrenergic
system by the PVN CRF neurons projecting to the
LC is responsible for the arousal response
during yawning induced by PVN stimulation or
stressful manipulation. However, we cannot rule
out the possibility that the pathways besides
the projection of CRF neurons to the LC
contribute to the arousal response during
yawning, since icy injection of a-helical CRF
could not completely block the arousal shift in
ECoG during yawning induced by PVN stimulation
in this study. We previously reported that
neurons responsible for yawning could be the
parvocellular oxytocinergic neurons in the PVN,
and it has been demonstrated that the
parvocellular oxytocinergic neurons in the PYN
send descending axons to the lower brain stem,
including the LC. Therefore, the descending
oxytocinergic system projecting to the LC also
may be involved in the arousal response during
yawning. This possibility should be investigated
further through the use of oxytocin antagonists
or higher doses of CRF antagonists.
In summary, we observed that electrical
stimulation of the PVN induced a stereotyped
yawning response, which was characterized by a
single large inspiration, an initial fall in BP,
and an arousal shift in the ECoG even after icy
injection of CRF antagonist, but that the
arousal response was significantly suppressed
compared to that after icy injection of saline.
These findings suggest that CRF neurons in the
PVN are primarily responsible for the arousal
response accompanying yawning behavior.
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administration of corticotropin-releasing factor
antagonist attenuates arousal response
accompanied by yawning behavior in rats.
Neurosci.Letter 2008;433(3):205-208
-Kita I, Yoshida
Y, Nishino S. An activation of parvocellular
oxytocinergic neurons in the paraventricular
nucleus in oxytocin-induced yawning and penile
erection. Neurosci Res. 2006;54(4):269-275
-Kita I,
Sato-Suzuki et al.Yawning responses induced
by local hypoxia in the paraventricular nucleus
of the rat.Beh Brain Res
2000;117(1-2):119-126
-Kubota N, Amemiya
S, Motoki C, Otsuka T, Nishijima T, Kita I.
Corticotropin-releasing factor antagonist
reduces activation of noradrenalin and serotonin
neurons in the locus coeruleus and dorsal raphe
in the arousal response accompanied by yawning
behavior in rats. Neurosci Res. 2012
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stimulation of paraventricular nucleus of the
rat Journal of Neurophysiology,
1998;80(5):2765-2775
-Seki Y, Y
Nakatani, et al Light induces cortical
activation and yawning in rat Behav Brain Res
2003;140(1-2):65-73
-Seki Y,
Sato-Suzuki I, et al Yawning/cortical
activation induced by microinjection of
histamine into the paraventricular nucleus of
the rat. Behav Brain Res.
2002;134(1-2):75-82.
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