Abstract
The paraventricular nucleus of the thalamus (PVT) projects to areas of the forebrain involved in behavior. Homeostatic challenges and salient cues activate the PVT and evidence shows that the PVT regulates appetitive and aversive responses. The brainstem is a source of afferents to the PVT and the present study was done to determine if the lateral parabrachial nucleus (LPB) is a relay for inputs to the PVT. Retrograde tracing experiments with cholera toxin B (CTB) demonstrate that the LPB contains more PVT projecting neurons than other regions of the brainstem including the catecholamine cell groups. The hypothesis that the LPB is a relay for brainstem signals to the PVT was assessed using an intersectional monosynaptic rabies tracing approach. Sources of inputs included the reticular formation, periaqueductal gray (PAG), nucleus cuneiformis, superior and inferior colliculi, and the LPB. Distinctive clusters of input cells to LPB-PVT projecting neurons were also found in the dorsolateral bed nucleus of the stria terminalis (BSTDL) and the lateral central nucleus of the amygdala (CeL). Anterograde viral tracing demonstrates that LPB-PVT neurons densely innervate all of the PVT in addition to providing collateral innervation to the preoptic area, lateral hypothalamus, zona incerta and PAG but not the BSTDL and CeL. The paper discusses the anatomical evidence that suggests that the PVT is part of a network of interconnected neurons involved in arousal, homeostasis, and the regulation of behavioral states with forebrain regions potentially providing descending modulation or gating of signals relayed from the LPB to the PVT.
Competing Interest Statement
The authors have declared no competing interest.
Abbreviations
- 3V
- third ventricle
- 4V
- fourth ventricle
- 7N
- facial nucleus
- ac
- anterior commissure
- aq
- aqueduct
- BLA
- basolateral amygdala
- BMA
- basomedial amygdala
- BSTDL
- bed nucleus of stria terminalis, dorsolateral
- BSTL
- bed nucleus of stria terminalis, lateral
- BSTM
- bed nucleus of stria terminalis, medial
- BSTV
- bed nucleus of stria terminalis, ventral
- BSTVL
- bed nucleus of stria terminalis, ventrolateral
- CeL
- central amygdala, lateral-capsular division
- CeM
- central amygdala, medial
- CnF
- nucleus cuneiformis
- cp
- cerebral peduncle
- CPu
- caudate putamen
- CTB
- cholera toxin subunit B
- DMH
- dorsomedial hypothalamus
- DR
- dorsal raphe
- dscp
- decussation superior cerebellar peduncle
- DT
- dorsal tegmental nucleus
- f
- fornix
- Hb
- habenular nucleus
- ic
- internal capsule
- IC
- inferior colliculus
- IMD
- intermediodorsal nucleus of thalamus
- IPAC
- interstitial nucleus of the posterior limb of the anterior commissure
- KF
- Killiker-Fuse nucleus
- LC
- locus ceruleus
- LH
- lateral hypothalamus
- LPB
- lateral aspect of the parabrachial nucleus
- LPO
- lateral preoptic area
- LRt
- lateral reticular nucleus
- LV
- lateral ventricle
- MD
- mediodorsal nucleus of thalamus
- MdRt
- medullary reticular nucleus
- Me5
- mesencephalic trigeminal nucleus
- mfb
- medial forebrain bundle
- MGN
- medial geniculate nucleus
- ml
- medial lemniscus
- MnPO
- median preoptic nucleus
- MPB
- medial aspect of the parabrachial nucleus
- MPO
- medial preoptic nucleus
- Mt
- mammillothalamic tract
- NAcSh
- shell of the nucleus accumbens
- NTS
- nucleus of the solitary tract
- opt
- optic tract
- PAG
- periaqueductal gray
- PAGD
- periaqueductal gray, dorsal
- PAGV
- periaqueductal gray, ventral
- PB
- parabrachialc nucleus
- PCRt
- parvicellular reticular nucleus
- PLH
- perifornical lateral hypothalamus
- POA
- preoptic area
- PSTh
- parasubthalamic hypothalamus
- PT
- paratenial nucleus of the thalamus
- PVN
- paraventricular nucleus of the hypothalamus
- PVT
- paraventricular nucleus of the thalamus
- aPVT
- anterior aspect of the paraventricular nucleus of the thalamus
- pPVT
- posterior aspect of the paraventricular nucleus of the thalamus
- py
- pyramidal tract
- RF
- reticular formation
- mRF
- mesencephalic reticular formation
- mdRF
- medullary reticular formation
- pRF
- pontine reticular formation
- rs
- rubrospinal tract
- SC
- superior colliculus
- scp
- superior cerebellar peduncle
- scpd
- superior cerebellar peduncle, descend limb
- sm
- stria medullaris of the thalamus
- SNL
- lateral substantia nigra
- sp5
- spinal trigeminal tract
- Sp5
- spinal trigeminal nucleus
- Sp5C
- spinal trigeminal nucleus, caudal
- STh
- subthalamic hypothalamus
- TH
- tyrosine hydroxylase
- TRIO
- tracing the input-output organization method
- Ve
- vestibular nucleus
- VLM
- ventrolateral medulla
- VMH
- ventromedial hypothalamus
- VP
- ventral pallidum
- ZI
- zona incerta
