NEUROSCIENCE
A central master driver of psychosocial stress
responses in the rat
Naoya Kataoka, Yuta Shima, Keisuke Nakajima, Kazuhiro Nakamura*
The mechanism by which psychological stress elicits various physiological responses is unknown.
We discovered a central master neural pathway in rats that drives autonomic and behavioral stress
responses by connecting the corticolimbic stress circuits to the hypothalamus. Psychosocial stress
signals from emotion-related forebrain regions activated a VGLUT1-positive glutamatergic pathway from
the dorsal peduncular cortex and dorsal tenia tecta (DP/DTT), an unexplored prefrontal cortical area,
to the dorsomedial hypothalamus (DMH), a hypothalamic autonomic center. Genetic ablation and
optogenetics revealed that the DP/DTT→DMH pathway drives thermogenic, hyperthermic, and
cardiovascular sympathetic responses to psychosocial stress without contributing to basal homeostasis.
This pathway also mediates avoidance behavior from psychosocial stressors. Given the variety of stress
responses driven by the DP/DTT→DMH pathway, the DP/DTT can be a potential target for treating
psychosomatic disorders.
P
sychological stressors induce various
physiological responses by stimulating
sympathetic, neuroendocrine, and behav-
ioral mechanisms. Stress-induced sym-
pathetic stimulation of thermogenic
and cardiovascular functions is common in
mammals and is recognized as a stress-coping
response to boost physical performance in
fight-or-flight situations. However, excessive
stress may cause aberrant sympathetic symp-
toms such as psychogenic fever, a hyperther-
mia caused by intense psychological stressors
( 1 ). Sympathetic thermogenesis in brown adi-
pose tissue (BAT) contributes to stress-induced
hyperthermia in rats and humans ( 2 , 3 ). Re-
sistance of psychogenic fever to antipyretics
indicates an etiology different from that of
infection-induced fever ( 1 ). Patients with post-
traumatic stress disorder exhibit augmented
cardiovascular responses to stress, which in-
crease the risk of developing hypertension and
cardiovascular diseases ( 4 ). Vigorous psycho-
genic cardiovascular responses are also observed
in panic disorder, a severe anxiety disorder ( 5 ).
However, the central circuit mechanisms by
which psychological stress activates the sympa-
thetic nervous system are not well understood.
The dorsomedial hypothalamus (DMH) is
an important brain site for sympathetic stress
responses ( 6 , 7 ). A hypothalamo-medullary path-
way from the DMH to sympathetic premotor
neurons in the rostral medullary raphe region
(rMR) mediates BAT thermogenic and cardio-
vascular responses to psychological stress ( 2 , 8 ).
However, the mechanism by which the cortico-
limbic circuits that process stress and emotion
activate the sympathoexcitatory DMH neurons
remains unknown. We sought to identify the
forebrain neural pathways that transmit stress
signals to the DMH by using functional neuro-
anatomy and in vivo physiological experiments
combining genetic lesion and optogenetic ma-
nipulations of a pathway of interest. We also
employed social defeat stress (SDS), an animal
model of psychosocial stress caused by inter-
individual relationships that mimics human
social stress ( 9 ).SDS activates DMH-projecting neurons
in the mPFC
To label neurons that project to the DMH, we
injected cholera toxin b subunit (CTb), a ret-
rograde neural tracer, into the rat DMH and
consequently found many CTb-labeled neu-
rons in the medial prefrontal cortex (mPFC)
(Fig. 1, A to C). Subsequent exposure to SDS
significantly increased expression of Fos, a
marker for neuronal activation, in CTb-labeled
neurons in specific mPFC subregions: the pre-
limbic cortex (PrL), infralimbic cortex (IL), and
dorsal peduncular cortex (DP) and the dorsal
tenia tecta (DTT) immediately rostral to the
callosal commissure (Fig. 1, D to F). These
double-labeled cells were mostly distributed
in layers V and VI and showed the typical mor-
phology of glutamatergic pyramidal neurons
(Fig. 1E). We did not find other forebrain re-
gions containing a substantial double-labeled
population after SDS.The DP/DTT mediates thermogenic and
cardiovascular sympathetic responses
to stress
The PrL and IL, which constitute the main
body of the mPFC ( 10 ), exert inhibitory effects
on stress responses ( 11 , 12 ). Correspondingly,
optogenetic stimulation of the IL→amygdala
or PrL→bed nucleus pathway reduces freez-
ing behavior in response to stress ( 13 , 14 ). No
literature is available on the function of the
DP and DTT (hereafter, the DP/DTT). Therefore,
we determined the roles of the stress-activatedmPFC subregions in driving sympathetic stress
responses.
SDS induced immediate increases in inter-
scapular BAT temperature (TBAT)andbodycore
(abdominal) temperature (Tcore)(Fig.2),repre-
senting psychosocial stress–induced BAT ther-
mogenesis and hyperthermia, respectively ( 8 ).
These responses were abolished by inactivation
of DP/DTT neurons with bilateral nanoinjec-
tions of muscimol: Responses were nearly sup-
pressed by injections of 200 nl per site (TBAT:
80% inhibition,Tcore: 88% inhibition; Fig. 2, A
to F) and were moderately inhibited by in-
jections of 100 nl per site (TBAT:63%inhibi-
tion,Tcore:54%inhibition;fig.S1).Incontrast,
muscimol injections of 200 nl per site into the
IL resulted in significantly reduced inhibition
of the responses (TBAT: 33% inhibition,Tcore:
26% inhibition; Fig. 2, G to L) compared with
injections into the DP/DTT (unpairedttests
comparing inhibition percentage;TBAT:t 8 =
3.16,P<0.05;Tcore:t 8 =2.82,P<0.05).SDS
also induced increases in heart rate (HR) and
mean arterial pressure (MAP), which were di-
minished by injections of muscimol (100 nl
per site) into the DP/DTT (HR: 53% inhibi-
tion, MAP: 77% inhibition; Fig. 2, M to Q).DP/DTT neurons drive sympathetic responses
through activation of the DMH→rMR pathway
To test whether DP/DTT neurons transmit
stress signals to the DMHtodrivesympathetic
responses, we performed in vivo electrophysio-
logical experiments in anesthetized rats. Stim-
ulation of DP/DTT neurons with nanoinjection
of bicuculline robustly increased BAT sym-
pathetic nerve activity (SNA),TBAT,HR,and
MAP (fig. S2, A to E) ( 15 ). All of these responses
were reversed by subsequent inactivation of
DMH neurons with muscimol injections (fig.
S2, A to E).
We next investigated whether the stimulation
of DP/DTT neurons activated the DMH→rMR
pathway. CTb injection into the rMR (fig. S2F)
retrogradely labeled many neurons that bilat-
erally clustered in the dorsal part of the DMH
(fig. S2, H and I); these include sympathoex-
citatory glutamatergic neurons driving cold-
defensive, febrile, and stress responses through
their innervation of sympathetic premotor
neurons in the rMR ( 8 , 16 – 18 ). Subsequent
stimulation of DP/DTT neurons with a uni-
lateral bicuculline injection under free-moving
conditions increased Fos expression in the CTb-
labeledpopulationintheDMH,mainlyipsi-
laterally to the site of bicuculline injection (fig.
S2, G to J).Glutamatergic innervation of DMH neurons by
DP/DTT neurons
Next, we determined the neurotransmitter that
mediates the DP/DTT→DMH transmission.
Transduction of DP/DTT neurons with palGFP,
a membrane-targeted form of green fluorescentRESEARCH
Kataokaet al.,Science 367 , 1105–1112 (2020) 6 March 2020 1of8
Department of Integrative Physiology, Nagoya University
Graduate School of Medicine, Nagoya 466-8550, Japan.
*Corresponding author. Email: [email protected] or
[email protected]