Distribution of neuropeptides in the limbic system of the rat: the hippocampus.
The distribution of several neuropeptides (vasoactive intestinal polypeptide, cholecystokinin octapeptide, substance P, neurotensin, methionine-enkephalin and somatostatin) in the hippocampal formation has been studied with immunocytochemical techniques. Numerous vasoactive intestinal polypeptide, cholecystokinin-octapeptide and somatostatin-positive cell bodies were found within the hippocampus and subiculum. Neurotensin-positive cell bodies were found within the subiculum, but no substance P or methionine-enkephalin-containing cell bodies were seen in either hippocampus proper or subiculum. Vasoactive intestinal polypeptide and cholecystokinin-octapeptide-positive cell bodies were predominantly located in the stratum moleculare and stratum radiatum of CA 1-2 regions and dentate gyrus, whilst somatostatin-containing cell bodies were found mainly in the stratum oriens. Nerve fibres containing each of the six peptides were found within the hippocampus. Large numbers of vasoactive intestinal polypeptide, cholecystokinin-octapeptide and somatostatin fibres innervated the pyramidal and granule cell layers, with smaller numbers in the stratum radiatum and fewer still in the stratum moleculare and stratum oriens. Other than a moderately dense neurotensin-positive fibre plexus in the dorsal subiculum, fewer neurotensin, substance P and methionine-enkephalin fibres were present. However, when present, these three peptides had a distribution restricted to a region close to the pyramidal layer in the CA 2/3 region and to the stratum moleculare of the CA 1 region. Peptide-containing fibres were identified entering or leaving the hippocampus in three ways, via (i) the fornix (all six peptides), (ii) the dorsal subiculum (neurotensin-positive fibres projecting to the cingulate cortex: somatostatin, vasoactive intestinal polypeptide, and cholecystokinin-octapeptide present in fibres running between the dorsal subiculum and occipito-parietal cortex) and (iii) the ventral subiculum (vasoactive intestinal polypeptide, cholecystokinin-octapeptide and somatostatin in fibres running between entorhinal cortex and hippocampus, and all six peptides in fibres crossing the amygdalo-hippocampal border). These findings indicate a major distinction between those peptides (vasoactive intestinal polypeptide, cholecystokinin-octapeptide, somatostatin, neurotensin) which are found in cell bodies intrinsic to the hippocampal formation and those peptides (substance P, methionine-enkephalin) which are found only in hippocampal afferents.(ABSTRACT TRUNCATED AT 400 WORDS)
D000818:Animals; D002766:Cholecystokinin / Q000378:metabolism; D004744:Enkephalin, Methionine / Q000378:metabolism; D006624:Hippocampus / Q000033:anatomy & histology / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D008297:Male; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009496:Neurotensin / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*; D051381:Rats; D013004:Somatostatin / Q000378:metabolism; D013373:Substance P / Q000378:metabolism; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D010455:Peptides; D013373:Substance P; D014660:Vasoactive Intestinal Peptide; D009496:Neurotensin; D013004:Somatostatin; D004744:Enkephalin, Methionine; D002766:Cholecystokinin