The distribution of tyrosine hydroxylase (TH)- and neuropeptide Y (NPY)-immunoreactive(IR) nerve fibers in the pineal complex was investigated in untreated rats and rats following bilateral removal of the superior cervical ganglia. In normal animals, a large number of TH- and NPY-IR nerve fibers were present in the pineal capsule, the perivascular spaces, and intraparenchymally between the pinealocytes throughout the superficial pineal and deep pineal gland. A small number of TH-IR and NPY-IR nerve fibers were found in the posterior and habenular commissures, a few fibers penetrating from the commissures into the deep pineal gland. To elucidate the origin of these fibers, the superior cervical ganglion was removed bilaterally in 10 animals, and the pineal complex was examined immunohistochemically. Two weeks after the ganglionectomy, the TH-IR and NPY-IR nerve fibers in the superficial pineal gland had almost completely disappeared. On the other hand, in the deep pineal and the pineal stalk, the TH-IR and NPY-IR fibers were still present after ganglionectomy. These data show that the deep pineal gland and the pineal stalk possess an extrasympathetic innervation by TH-IR and NPY-IR fibers. It is suggested that the extrasympathetic TH-IR and NPY-IR nerve fibers innervating the deep pineal and the pineal stalk originate from the brain.

Summary:The purpose of the present study was to ex amine the effect of blockade of N-methyl-o-aspartate (NMDA) receptors on the depolarization associated with severe hypoglycemia, which is commonly preceded by one or a few transient depolarizations reminiscent of cor tical spreading depression (CSD). In the cerebral cortices of rats [K + le and [Ca2 + le were measured with ion selective microelectrodes. NMDA blockade was achieved by injection of MKSOI in doses that block CSD. In control rats, the latency from the time point when blood glucose reached minimal levels to onset of ionic shifts was 33.2 ± 3.5 min, and [K +le rose from 3.2 ± 0.2 to 55 ± 5 mM. All variables remained unchanged in ratsThe aim of the present study was to examine the mechanism of change of extracellular ionic activi ties associated with severe hypoglycemia (Astrup and Norberg 1976; Harris et aI., 1984). Previous studies have shown that the tissue concentrations of labile phosphates and energy charge remain con stant immediately preceding the large cortical changes of [K+]e and [Ca 2 +]e (Harris et aI., 1984). Therefore, the triggering of hypoglycemic depolar ization is not explained simply by a decline of en ergy metabolism.After onset of depolarization, the level of cortical ATP and phosphocreatine (PCr) decrease rapidly,

Summary: This study describes the distribution of pep tide sequences derived from the prepro-vasoactive intes tinal polypeptide (preproVIP) molecule in perivascular nerves of rat brain arteries and arterioles. The peptides were identified by immunohistochemistry using highly specific antibodies. Five peptide sequences (preproVIP 60-76, peptide histidine isoleucine (PHI), preproVIP 111-122, VIP, and preproVIP 15�170) were identified in the perivascular nerves throughout the arterial cerebral cir culation. The density of the immunoreactive fibers was highest in the nerves of the larger extracerebral arteries, declining in smaller branching arteries. All peptide se quences were identified in the nerves of small pial arte rioles overlying the cortical convexity, whereas capillar ies and veins contained no immunoreactive material. Rat vasoactive intestinal polypeptide (VIP) issynthesized from a precursor, preproVIP, consist ing of about 170 amino acid residues (Nishizawa et aI., 1985). PreproVIP can be divided functionally into six domains (Nishizawa et aI., 1985) that in clude the amino acid sequences of VIP and peptide histidine isoleucine (PHI), which are biologically active (e.g. Edvinsson and McCulloch, 1985). Other Abbreviations used: BA, basilar artery; ICA, inferior cerebel lar artery; PBS, potassium-phosphate-buffered saline; PBS-TX, PBS containing Triton X-IOO; PHI, peptide histidine isoleucine; SCA, superior cerebellar artery; VA, vertebral artery; VIP, va soactive intestinal polypeptide. 932Dendritic processes of neocortical neurons immunoreac tive for VIP and PHI could be followed towards the brain surface where the processes penetrated into the pial layer, often close to the pial vasculature. Some of the processes were also observed to enter the Virchow-Robin space, close to the arterioles. It is possible that cortical nerve cells containing VIP and PHI release the peptides in the perivascular space during periods of activity and thereby contribute to local vasodilatation associated with changes of neuronal function. Key Words: Vasoactive in testinal polypeptide (VIP)-Peptide histidine isoleucine VIP precursor-Immunohistochemistry-Radioimmuno assay-Cerebral blood vessels-Innervation-Rat Metabolic autoregulation.