CRUSTACEAN CARDIOACTIVE PEPTIDE-IMMUNOREACTIVE NEURONS INNERVATING BRAIN NEUROPILS, RETROCEREBRAL COMPLEX AND STOMATOGASTRIC NERVOUS-SYSTEMOF THE LOCUST, LOCUSTA-MIGRATORIA

The distribution and morphology of crustacean cardioactive peptide-imm unoreactive neurons in the brain of the locust Locusta migratoria has been determined. Of more than 500 immunoreactive neurons in total, abo ut 380 are interneurons in the optic lobes. These neurons invade sever al layers of the medulla and distal parts of the lobula. In addition, a small group of neurons projects into the accessory medulla, the lami na, and to several areas in the median protocerebrum. In the midbrain, 12 groups or individual neurons have been reconstructed. Four groups innervate areas of the superior lateral and ventral lateral protocereb rum and the lateral horn. Two cell groups have bilateral arborizations anterior and posterior to the central body or in the superior median protocerebrum. Ramifications in subunits of the central body and in th e lateral and the median accessory lobes arise from four additional ce ll groups. Two local interneurons innervate the antennal lobe. A trito cerebral cell projects contralaterally into the frontal ganglion and a ppears to give rise to fibers in the recurrent nerve, and in the hypoc erebral and ingluvial ganglia. Varicose fibers in the nervi corporis c ardiaci III and the corpora cardiaca, and terminals on pharyngeal dila tor muscles arise from two subesophageal neurons. Some of the locust n eurons closely resemble immunopositive neurons in a beetle and a moth. Our results suggest that the peptide may be (1) a modulatory substanc e produced by many brain interneurons, and (2) a neurohormone released from subesophageal neurosecretory cells.