cardiovascular-agents and proctolin

In the present paper, the literature describing synthetic, biological and conformational studies on the insect neuropeptide proctolin (H-Arg-Tyr-Leu-Pro-Thr-OH) and its analogues is summarized. The paper covers proctolin and its 80 analogues modified in positions 1-5, a cycloanalogue and analogues with a truncated or elongated peptide chain. These peptides were bioassayed by different methods, e.g. studies of myotropic activities in several insect species in vitro and behaviour in rats in vivo. Based on these data structure-activity relationships are discussed.

Topics: Amino Acid Sequence; Analgesics; Animals; Cardiovascular Agents; Humans; Insecta; Muscles; Neuropeptides; Neurotransmitter Agents; Oligopeptides; Protein Conformation; Rats; Structure-Activity Relationship

The heart of Bathynomus doederleini gives rise to an anterior median artery (AMA), one pair of anterior lateral arteries (ALAs) and five pairs of lateral arteries (LAs). Cardioarterial valves are located at the junctions between the heart and arteries, each composed of a pair of muscular flaps. All valves of the AMA and the ALAs receive valve excitatory (constrictor) nerves (VEs). The valves of the ALAs receive dual innervation from both constrictor and inhibitor (dilator) nerves, while the valves of the AMA receive innervation from a constrictor nerve alone. The effects of candidate neurohormones on cardioarterial valves were examined by measuring the pressure in each artery at which haemolymph flows out of the heart through the valve. Serotonin, octopamine, norepinephrine, glutamate (Glu) and proctolin constricted the cardioarterial valves and thus decreased the arterial pressure in all the arteries. Dopamine also decreased the arterial pressure of arteries except for the ALAs, in which pressure was increased. Among the neurohormones exerting excitatory effects on the valves, only Glu depolarized the membrane potential of valve muscle cells. The glutamatergic agonists kainate and quisqualate also depolarized the valve muscle cells of the AMA. Excitatory junctional potentials produced in the valves of the AMA in response to the stimulation of a VE were blocked by the glutamatergic antagonists Joro spider toxin and MK-801. Glu is the likeliest candidate for a neurotransmitter for the VEs.

Topics: Acetylcholine; Animals; Arteries; Cardiovascular Agents; Cardiovascular System; Central Nervous System; Crustacea; Dopamine; Dose-Response Relationship, Drug; Excitatory Amino Acid Agents; Glutamic Acid; Heart; Heart Valves; Immunohistochemistry; Membrane Potentials; Neuropeptides; Neurotransmitter Agents; Norepinephrine; Octopamine; Oligopeptides; Serotonin