Enkephalinergic rostral hypothalamic neurones do not project to the intermediate PAG in the rat

Retrograde transport of fluorescent latex microspheres was combined with immunocytochemistry to determine whether enkephalinergic neurones in the rostral hypothalamus project to the intermediate periaqueductal grey. Distributions of retrogradely labelled neurones and neurones immunoreactive for enkephalins were as expected from previous studies. However, very few neurones contained both markers suggesting that enkephalinergic neurones in the rostral hypothalamus do not project to the periaqueductal grey at this level. A series of control experiments was carried out on a pathway with a known enkephalinergic component to confirm the compatibility of this combination of techniques.