Techniques for histological reconstruction of brain stem recording sites.

The masseter muscle of Sprague-Dawley rats was injected with 10 mg of horseradish peroxidase. The electrical activity of the trigeminal motor nucleus was investigated 24-36 hours later using micropipettes filled with a 2.0 M NaCl-7% fast green FCF solution. A parallel series of penetrations at 200 micron intervals was made through the motor complex at known depths. The grid formed from these penetrations was reconstructed using the following techniques. Marks were made at known depths in one or more of the tracts by iontophoresing fast green from the microelectrode tip with a hyperpolarizing current of 10 muA for 10 minutes. To assure proper alignment of the tissue containing the green marks, two agar-India ink plugs were placed caudal and parallel to the recording sites. The frozen tissue was sectioned on a microtome, first through the agar plugs and then through the tissue containing the green marks. The tissue could be incubated for the peroxidase reaction product or stained for Nissl substance. These combined procedures offer a means to correlate the structure and function of brain stem nuclear groups.     

Autocrine endothelial regulation in brain stem vessels of newborn piglets.

Vasoactive intestinal peptide (VIP) is known as a potent regulator for the development of the central nervous system (CNS). The neonatal period of brain development is characterised by rapid cellular proliferation in parallel with neuronal differentiation and angiogenesis. We examined the expression of native VIP and the VIP receptor-associated protein by immunohistochemistry as well as the expression of VIP mRNA by in situ hybridisation in the brain stem of newborn piglets. We found both the mRNA and the protein of VIP as well as the VIP receptor-associated protein in endothelial cells of veins, arteries and capillaries in the marginal zone of brain stem tissue sections, especially in pons and mesencephalon, as well as in pial vessels. The coexpression of native VIP, VIP mRNA and the VIP receptor-associated protein within the endothelium suggests the presence of an autocrine loop, which has been detected so far only in neuroblastoma cells. This expression pattern gives evidence to the immaturity of endothelial cells at birth and the presence of an adaptive response in the VIP-regulated system during the change from intra- to extrauterine life.