Novel peptide pancreastatin: Its occurrence and codistribution with chromogranin a in the central nervous system of the pig

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Abstract
The distribution of pancreastatin immunoreactivity was investigated in porcine brain, spinal cord, dorsal root ganglia, and pituitary. In the brain, immunoreactive cell bodies were present in many areas including the cortex, basal ganglia, hippocampus, thalamus, hypothalamus, mesencephalic reticular formation, cerebellum, and medulla oblongata. Immunoreactive fibres were most abundant in the globus pallidus, stria terminalis, entopeduncular nucleus, hippocampus, and in the substantia nigra. In the spinal cord, immunoreactive cells were found in laminae IV±IX. Immunoreactive fibres were concentrated in the dorsal horn. Pancreastatin immunoreactivity was localised to fibres and small cells (5–10% of the total) in the dorsal root ganglia. In the posterior pituitary, many immunoreactive fibres were present and in the anterior lobe subsets of gonadotrophs and thyrotrophs were pancreastatin‐immunoreactive. The localisation of pancreastatin showed a parallel distribution with chromogranin A. Coexistence of pancreastatin with calcitonin generelated peptide (CGRP) immunoreactivity in cell bodies in the spinal cord, including motoneurones, and with CGRP or galanin immunoreactivities in dorsal root ganglion cells was also noted. The differential pattern of pancreastatin immunostaining was reflected in the extractable levels of peptide with highest concentrations in the cortex (55.8 ± 6.0 pmol/g wet weight, mean ± S.E.M.), thalamus (60.0 ± 5.0 pmol/g), hypothalamus (54.4 ± 6.5 pmol/g), and anterior pituitary (2,714 ± 380 pmol/g). Characterisation of pancreastatin immunoreactivity in the hypothalamus and pituitary by gel permeation and high‐pressure liquid chromatography revealed multiple molecular forms, one of which was indistinguishable from natural porcine pancreastatin. The widespread distribution of pancreastatin immunoreactivity suggests this peptide may play a part in several neuroendocrine, autonomic, somatic, and sensory functions, and its colocalisation with chromogranin A is consistent with a precursor‐product relationship.