Fc. Barone et al., RETICULAR THALAMIC INHIBITORY INPUT TO LATERAL HYPOTHALAMIC NEURONS -A FUNCTIONAL AND HISTOCHEMICAL DETERMINATION, Brain research bulletin, 33(5), 1994, pp. 575-582
Both the lateral hypothalamus (LH) and reticular thalamus (RT) have be
en implicated in the integration of a variety of vital functions. To d
etermine relevant connections more specifically between cells of these
two regions in the rat, functional neurophysiological and horseradish
peroxidase (HRP) histochemical techniques were utilized. Single pulse
electrical stimulation of the RT modified the discharge frequency of
the majority of LH neurons tested. LH neuronal responses to RT stimula
tion included; inhibition (66.32%), excitation followed by inhibition
(6.12%), and excitation (7.14%). Because RT stimulation resulted prima
rily in the inhibition of LH neuronal activity with a relative short m
ean latency of 1.87 +/- 0.23 ms, the existence of a possible direct in
hibitory pathway from the RT to LH also was evaluated using HRP histoc
hemistry. Retrogradely HRP labeled soma were identified in the RT afte
r HRP was ejected extracellularly onto LH neurons, which exhibited a d
ecrease in spontaneous activity in response to RT stimulation. These d
ata demonstrate direct projections from the RT to the LH. In addition,
HRP labeling of neurons and axons in the zona incerta-LH area followi
ng LH HRP ejections suggest this route as a synaptic pathway from RT t
o LH.