Table 3.

Densities of varicosities labeled for arousal neurotransmitters or anterograde tracer in the VLPO core (average of two to three cases each)

Source of fibersVaricosities per mm2
Histamine36,000
Dopamine-β-hydroxylase (noradrenaline)32,300
Serotonin transporter30,200
Phenyl-ethanolamine-N-methyl transferase (adrenaline)5,700
Orexin7,700
Choline acetyltransferase550
Infralimbic cortex13,400
Lateral septal nucleus21,800
Median preoptic nucleus15,225
Medial preoptic area1,850
Suprachiasmatic nucleus1,050
Subparaventricular zone1,300
Dorsomedial hypothalamic nucleus25,300
Ventromedial hypothalamic nucleus1,100
Lateral hypothalamic area3-a6,350
Medial amygdala1,200
Supramammillary nucleus933
Lateral parabrachial nucleus12,850
  • Moderate to heavy inputs (>10,000 varicosities per square millimeter) are highlighted in bold text. Monoaminergic terminals provide the apparently densest inputs to the VLPO, despite the relatively low numbers of retrogradely labeled monoaminergic neurons.

  • F3-a The lateral hypothalamic area (LHA) is a particularly large brain region in the rat, and our anterograde tracer injections filled only a small fraction of this area; hence, varicosities arising from LHA injections may underestimate the intensity of this afferent to the VLPO.