Abstract
The ventral pallidum (VP) is a key component of the cortico-basal ganglia circuits that process motivational and emotional information, and also a crucial site for reward. Although the main targets of the two VP compartments, medial (VPm) and lateral (VPl) have already been established, the collateralization patterns of individual axons have not previously been investigated. Here we have fully traced eighty-four axons from VPm, VPl and the rostral extension of VP into the olfactory tubercle (VPr), using the anterograde tracer biotinylated dextran amine in the rat. Thirty to fifty percent of axons originating from VPm and VPr collateralized in the mediodorsal thalamic nucleus and lateral habenula, indicating a close association between the ventral basal ganglia-thalamo-cortical loop and the reward network at the single axon level. Additional collateralization of these axons in diverse components of the extended amygdala and corticopetal system supports a multisystem integration that may take place at the basal forebrain. Remarkably, we did not find evidence for a sharp segregation in the targets of axons arising from the two VP compartments, as VPl axons frequently collateralized in the caudal lateral hypothalamus and ventral tegmental area, the well-known targets of VPm, while VPm axons, in turn, also collateralized in typical VPl targets such as the subthalamic nucleus, substantia nigra pars compacta and reticulata, and retrorubral field. Nevertheless, VPl and VPm displayed collateralization patterns that paralleled those of dorsal pallidal components, confirming at the single axon level the parallel organization of functionally different basal ganglia loops.
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Abbreviations
- AA:
-
Anterior amygdaloid area
- ac:
-
Anterior commissure
- aca:
-
Anterior commissure anterior part
- acp:
-
Anterior commissure posterior part
- Acb:
-
Nucleus accumbens
- AcbC:
-
Nucleus accumbens, core
- AcbSh:
-
Nucleus accumbens, shell
- AD:
-
Anterodorsal thalamic nucleus
- AM:
-
Anteromedial thalamic nucleus
- AON:
-
Anterior olfactory nucleus
- Atg:
-
Anterior tegmental nucleus
- B:
-
Basal nucleus of Meynert
- BDA:
-
Biotinylated dextran amine
- BSTL:
-
Bed nucleus of the stria terminalis, lateral division
- BSTM:
-
Bed nucleus of the stria terminalis, medial division
- C:
-
Caudal
- CalB:
-
Calbindin D28k
- CG:
-
Central gray
- Cl:
-
Claustrum
- CLi:
-
Caudal linear nucleus of raphe
- CPu:
-
Caudate putamen
- D:
-
Dorsal
- DMTg:
-
Dorsomedial tegmental area
- DR:
-
Dorsal raphe
- DpMe:
-
Deep mesencephalic nucleus
- EA:
-
Extended amygdala
- Enk:
-
Leucine-Enkephalin
- EP:
-
Entopeduncular nucleus
- f:
-
Fornix
- fr:
-
Fasciculus retroflexus
- GP:
-
Globus pallidus
- GPe:
-
External globus pallidus
- GPi:
-
Internal globus pallidus
- HDB:
-
Horizontal limb of the diagonal band of Broca
- ic:
-
Internal capsule
- ICj:
-
Islets of Calleja
- IP:
-
Interpeduncular nucleus
- IPAC:
-
Interstitial nucleus of posterior limb of anterior commissure
- L:
-
Lateral
- LacbSh:
-
Lateral acumbens shell
- LDDM:
-
Laterodorsal thalamic nucleus, dorsomedial part
- LDTg:
-
Laterodorsal tegmental nucleus
- LH:
-
Lateral hypothalamic area
- LHb:
-
Lateral habenula
- LM:
-
Lateral mammillary nucleus
- LOT:
-
Nucleus of the lateral olfactory tract
- LPO:
-
Lateral preoptic area
- LSI:
-
Lateral septal nucleus intermediate part
- LSS:
-
Lateral stripe of striatum
- LSV:
-
Lateral septal nucleus, ventral part
- LV:
-
Lateral ventricle
- MCPO:
-
Magnocellular preoptic area
- MD:
-
Mediodorsal thalamic nucleus
- MeA:
-
Medial amygdaloid area
- MHb:
-
Medial habenula
- mp:
-
Mammillary peduncle
- MPA:
-
Medial preoptic area
- MT:
-
Medial terminal nucleus of the accessory optic tract
- MTu:
-
Medial tuberal nucleus
- opt:
-
Optic tract
- PaR:
-
Pararubral area
- PF:
-
Parafascicular thalamic nucleus
- PMnR:
-
Paramedian raphe nucleus
- PnO:
-
Pontine reticular nucleus, oral part
- PnC:
-
Pontine reticular nucleus, caudal part
- PPTg:
-
Pedunculopontine tegmental nucleus
- PS:
-
Parastrial nucleus
- PVA:
-
Paraventricular thalamic nucleus, anterior part
- R:
-
Red nucleus
- Rbd:
-
Rhabdoid nucleus
- Re:
-
Reuniens thalamic nucleus
- Rh:
-
Rhomboid thalamic nucleus
- RPF:
-
Retroparafascicular nucleus
- RRF:
-
Retrorubral field
- Rt:
-
Reticular thalamic nucleus
- RtTg:
-
Reticulotegmental nucleus of the pons
- Sib :
-
Substantia innominata, basal part
- SHy:
-
Septohypothalamic nucleus
- SLEAr:
-
Rostral sublenticular extended amygdala
- sm:
-
Stria medullaris
- SMT:
-
Submammillothalamic nucleus
- SN:
-
Substantia nigra
- SNc:
-
Substantia nigra pars compacta
- SNl:
-
Substantia nigra pars lateralis
- SNr:
-
Substantia nigra pars reticulata
- STh:
-
Subthalamic nucleus
- StHy:
-
Striohypothalamic nucleus
- Sub:
-
Submedius thalamic nucleus
- SubCV:
-
Subcoeruleus nucleus, ventral part
- SubI:
-
Subincertal nucleus
- SuM:
-
Supramammillary nucleus
- Tu:
-
Olfactory tubercle
- VA:
-
Ventral anterior thalamic nucleus
- VLPAG:
-
Ventrolateral periaqueductal gray
- VLTg:
-
Ventrolateral tegmental nucleus
- VM:
-
Ventromedial thalamic nucleus
- VP:
-
Ventral pallidum
- VPl:
-
Ventral pallidum, dorsolateral compartment
- VPm:
-
Ventral pallidum, ventromedial compartment
- VPr:
-
Ventral pallidum, rostral portion
- VTA:
-
Ventral tegmental area
- VTg:
-
Ventral tegmental nucleus
- ZI:
-
Zona incerta
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Acknowledgments
We thank John F. Wesseling and Julio Artieda for critical readings of the manuscript and John F. Wesseling and Manuel Alegre for assistance with the electrophysiology. We also thank Francisco Clascá for donating the Sindbis virus vector for the Supplementary material. Anushree Tripathi is recipient of a predoctoral grant from FIMA (Foundation for Applied Medical Research). This work was supported by the Spanish Ministry of Education and Science (MEC, BFU2004-06825), Gobierno de Navarra 2004, and the ‘UTE project CIMA’.
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Tripathi, A., Prensa, L. & Mengual, E. Axonal branching patterns of ventral pallidal neurons in the rat. Brain Struct Funct 218, 1133–1157 (2013). https://doi.org/10.1007/s00429-012-0451-0
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DOI: https://doi.org/10.1007/s00429-012-0451-0