Presence of galanin in dopaminergic neurons of the sheep infundibular nucleus: a double staining immunohistochemical study

The distribution of tyrosine hydroxylase (TH) and of galanin immunoreactive (IR) neurons were examined in the sheep infundibular nucleus. Antisera rai sed against TH and galanin were used on adjacent sections and for double im munohistochemical staining of the same sections. There was considerable ove rlap in the distribution of TH and galanin-IR neurons in the medial part of the nucleus. Most of the galanin-IR neurons were also TH-IR, but less than 50% of the TH-IR neurons also expressed galanin immunoreactivity. Neurons immunoreactive to TH alone were observed close to the third ventricle and i n the rostral part of the infundibular nucleus. In the median eminence, TH and galanin-IR fibres overlapped mainly in the lateral and dorsal parts of the external layer, but the colocalisation of both antigens could not be as sessed on the available material. Thus, in sheep, the population of catecho laminergic neurons of the infundibular nucleus may be subdivided into diffe rent subpopulations according to their peptide content, but does not appear segregated as in rat and human. (C) 1998 Elsevier Science B.V. All rights reserved.