CL-3 ADRENERGIC MEDULLARY NEURONS PROJECT TO THE PARAVENTRICULAR THALAMIC NUCLEUS IN THE RAT

Adrenergic afferents to the thalamus are almost entirely concentrated in the paraventricular thalamic nucleus (PV). The origins of this proj ection from medullary C1-3 neurones were quantified, using a combinati on of retrograde fluorescent markers and immunocytochemical localisati on for phenylethanolamine N-methyltransferase (PNMT) in the rat. C1 ne urones contributed 51%, C2 29% and C3 20% of the total adrenergic inpu t. Many apparently non-adrenergic retrogradely labelled neurones were also found amongst the C1-3 neurones. The C3 region contained the larg est adrenergic population (67%) of retrogradely labelled neurones. The neuronal networks associated with PV suggest a role for these adrener gic projections in regulating specific autonomic, locomotor and behavi oural events.