Neuropeptide proctolin associated with an identified skeletal motoneuron

Abstract

Our objective was to find large and identifiable peptide-containing neurons and their postsynaptic targets. For this, a whole mount immunohistochemical method was used to locate cell bodies of neurons in the cockroach central nervous system immunoreactive to antibodies raised against the pentapeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH).The morphology and projections of the immunoreactive neurons were investigated by combining intracellular dye injection and electrophysiological and immunochemical procedures. The presence of proctolin in specific immunoreactive neurons was check by high pressure liquid chromatography combined with bioassay applied to extracts made from individually identified and isolated cell bodies.Using these approaches, we have identified a large proctolin-containing motoneuron which innervates muscles in a proximal segment of the cockroach leg. This study establishes a well characterized cellular preparation in which the physiological actions and functions of a peptidecontaining neuron can be studied in vivo.Proctolin was described initially as a myotropic peptide and proposed as a candidate neurotransmitter in the hindgut or proctodeum of the American cockroach Periplaneta americana (Brown, 1967(Brown, ,1975Brown and Starratt, 1975). Later, it was extracted, purified, and sequenced from 125 kg of whole cockroach (Starratt and Brown, 1975) and shown to have the following structure: H-Arg-Tyr-Leu-Pro-Thr-OH.The presence of proctolin in the proctodeal nerves and the similarity of contractions of the hindgut produced either by nerve stimulation or application of proctolin (Brown, 1975)

Evidence for parallel actions of a molluscan neuropeptide and serotonin in mediating arousal in Aplysia.

“…Serotonin at 1 mM produced no statistically significant greater stimulation of cAMP than serotonin at 0.1 mM ( Evidence obtained in other preparations in vertebrates and invertebrates suggests that the presence of parallel aminergic and peptidergic pathways that mediate similar actions may be widespread (13)(14)(15)(16)(17). In some instances an amine and a peptide may be released from the same neuron (18,19), and we cannot exclude the interesting possibility that SCPB is a cotransmitter with serotonin in neurons other than the MCC or perhaps a cotransmitter with acetylcholine, the excitatory transmitter at the ARC muscle (4).…”

Functional organization of cotransmission systems: Lessons from small nervous systems

“…The now classic work from the O'Shea laboratory (Adams and O'Shea, 1983;Bishop and O'Shea, 1982;O'Shea and Bishop, 1982) demonstrated that proctolin was colocalized with glutamate in the Ds (slow coxal depressor) motor neurons of the cockroach. These authors then attempted to determine whether there were defined postjunctional actions that could be attributed separately to glutamate and to proctolin.…”

A single allatostatin-immunoreactive neuron innervates skeletal muscles of several segments in the locust

“…A similar selectivity is prominent in the crustacean Idotea, in which only two to four fibers within the five to eight fibers of each dorsal extensor muscle receive Dip-AST 7-ir innervation (Kreissl et al, 1999). Selective distribution of peptidergic innervation within muscles also has been found for proctolin in the extensor tibiae of the locust and in Drosophila (O'Shea and Bishop, 1982;Anderson et al, 1988).…”