DISTRIBUTION OF CALRETININ, CALBINDIN-D28K AND PARVALBUMIN IN THE HYPOTHALAMUS OF THE SQUIRREL-MONKEY

The immunohistochemical approach was used to study the distribution of three calcium-binding proteins of the 'EF hand' family, namely calret inin, calbindin-D28k and parvalbumin, in the preoptico-hypothalamic co mplex of the squirrel monkey (Saimiri sciureus). These three calcium-b inding proteins were found to be heterogeneously distributed in the pr imate hypothalamus. Neurons expressing high levels of calretinin immun oreactivity were particularly abundant in the infundibular (arcuate) n ucleus, the suprachiasmatic nucleus, the lateral area and the dorsomed ial nucleus of the hypothalamus. Neurons displaying immunoreactivity f or calbindin-D28k were especially numerous in the medial preoptic area and diagonal band nucleus, as well as in the magnocellular subdivisio n of the paraventricular nucleus, the suprachiasmatic nucleus, the sup raoptic nucleus, the infundibular nucleus, the ventromedial nucleus an d the mammillary bodies of the hypothalamus. Fibers displaying intense immunoreactivity for either calretinin or calbindin-D28k were very ab undant in the median eminence of the hypothalamus. In contrast to calr etinin-and calbindin-D28k, parvalbumin was largely absent from the pri mate preoptico-hypothalamic complex. Parvalbumin-immunoreactive neuron s occurred in significant number only in the most lateral portion of t he medial mammillary nucleus in the squirrel monkey. The results of th e present study suggest that calretinin and calbindin-D28k may act, ei ther in concert or in a complementary manner, so as to participate in some specific aspects of the multifarious role of the hypothalamus in primates. In contrast to the other two calcium-binding proteins, parva lbumin is unlikely to be involved in a significant manner in hypothala mic functions in primates. (C) 1997 Elsevier Science B.V.