Fig. 6.

LO/VLO pyramidal neurons send collaterals to both hypothalamus and PAG. Terminals in the Gemini (Gem) and reticulotegmental nucleus (RtTg). Axons terminating in the parvafox nucleus are the collaterals of fibres that continue their course distally to innervate the ventrolateral PAG. Transverse sections through the rat OFC after fluorogold (A, C) and BDA (B, D), had been simultaneously injected into the ventrolateral region of the hypothalamus that harbours the parvafox nucleus (fluorogold) and into the ventrolateral region of the PAG in which the Su3- and the PV2 nuclei reside (BDA). Pyramidal cells in layers V–VI of the LO/VLO-cortex were double-labelled (white arrows in C, D) with two different retrogradely transported dyes. Fluorogold injected in the ventrolateral hypothalamus revealed the presence of a larger number of labelled neurons in the orbital and the medial portions of the prefrontal cortex than did BDA injected in the ventrolateral PAG. OL olfactory lobe, RhF rhinal fissure, I–VI cortical layers. Scale bars: A, B 0.3 mm; C, D 0.03 mm. E The ipsilateral nucleus Gemini (Gem), receives a strong innervation, particularly from the LO-cortex, visible also on the contralateral side. Notice the tendril-like bundle of axons (arrowheads) joining the nucleus Gemini from the ventromedial part of the cerebral peduncle. Scale bar 0.5 mm. F In this parasagittal section (rostral to the right), in addition to PBP and PN, also the rich innervation of the reticulotegmental nucleus (RtTg) is visible. A large number of axons perpendicular to the brain surface course in the isthmic reticular formation (isRt) to innervate the laterodorsal tegmental nucleus (LDTg). Scale bar: 0.5 mm