CANNABINOID RECEPTOR-BINDING DID NOT VARY IN SEVERAL HYPOTHALAMIC NUCLEI AFTER HYPOTHALAMIC DEAFFERENTATION

Cannabinoid receptors are sparsely distributed in the hypothalamic nuc lei, although they seem to be located on key neurons because their act ivation produces important neuroendocrine effects. In the present stud y, we have examined whether cannabinoid receptor-containing hypothalam ic neurons are intrinsic or extrinsic to this brain region. To this en d, we have examined whether the hypothalamic deafferentation was follo wed by a general loss of cannabinoid receptor binding, thus suggesting that cannabinoid receptor-containing neurons would have their cell bo dies outside the hypothalamus, or whether this was followed by no chan ges in binding, thus suggesting that cannabinoid receptors would be lo cated on intrinsic neurons. Three experimental groups were then analyz ed: (i) animals with complete hypothalamic deafferentation in both sid es; (ii) hemideafferentated animals; and (iii) sham-operated animals. In the three cases, cannabinoid receptor binding did not vary among th ese three groups in any of the hypothalamic nuclei analyzed. These wer e the arcuate nucleus, ventromedial hypothalamic nucleus, lateral and dorsal hypothalamic areas, paraventricular nucleus and medial preoptic area. This clearly supports the view that cannabinoid receptor-contai ning neurons into the hypothalamus are all intrinsic to this brain reg ion.