Studies on the Hypotensive, Cardio-suppressant, Vasodilator and Antiplatelet Activities of Betel Nut Crude Extract and its Constituents

Cholinergic structures in the arm of the cephalopod Octopus vulgaris were studied by immunohistochemistry using specific antisera for two types (common and peripheral) of acetylcholine synthetic enzyme choline acetyltransferase (ChAT): antiserum raised against the rat common type ChAT (cChAT), which is cross-reactive with molluscan cChAT, and antiserum raised against the rat peripheral type ChAT (pChAT), which has been used to delineate peripheral cholinergic structures in vertebrates, but not previously in invertebrates. Western blot analysis of octopus extracts revealed a single pChAT-positive band, suggesting that pChAT antiserum is cross-reactive with an octopus counterpart of rat pChAT. In immunohistochemistry, only neuronal structures of the octopus arm were stained by cChAT and pChAT antisera, although the pattern of distribution clearly differed between the two antisera. cChAT-positive varicose nerve fibers were observed in both the cerebrobrachial tract and neuropil of the axial nerve cord, while pChAT-positive varicose fibers were detected only in the neuropil of the axial nerve cord. After epitope retrieval, pChAT-positive neuronal cells and their processes became visible in all ganglia of the arm, including the axial and intramuscular nerve cords, and in ganglia of suckers. Moreover, pChAT-positive structures also became detectable in nerve fibers connecting the different ganglia, in smooth nerve fibers among muscle layers and dermal connective tissues, and in sensory cells of the suckers. These results suggest that the octopus arm has two types of cholinergic nerves: cChAT-positive nerves from brain ganglia and pChAT-positive nerves that are intrinsic to the arm.

Immunohistochemical localization of two types of choline acetyltransferase in neurons and sensory cells of the octopus arm

The predatory behaviour of the cuttlefish has been the subject of a few detailed studies and can be divided into several stages: prey detection, orientation, positioning, prey-seizing, prey-manipulation and ingestion. Nevertheless, the data about its control by the CNS remain fragmentary. By injecting a cholinergic agonist (nicotine) and antagonists (α-bungarotoxin, mecamylamine), the implication of cholinergic networks of the anterior basal and inferior frontal lobes in the control of predatory behaviour are demonstrated. Through these cholinergic networks, the anterior basal lobe takes an important part in the orientation and positioning. The inferior frontal lobe seems to play a role in the control of brachial manipulative and buccal mass activities. The implication of cholinergic networks of the anterior basal and inferior frontal lobes in the predatory behaviour and the pharmacology of nicotinic receptors are discussed.

The role of cholinergic networks of the anterior basal and inferior frontal lobes in the predatory behaviour of Sepia officinalis

In vitro experiments were performed on a standardized preparation of the autonomously contractile bulbus cordis branchialis of the branchial heart of Sepia officinalis to investigate its cholinergic neuroregulation. Apart from acetylcholine, nicotine and carbachol (nicotinic agonists), the muscarinic agonists muscarine, arecoline, pilocarpine, and oxotremorine also exerted concentration-dependent negative inotropic effects on the preparations. As both the muscarinic antagonist quinuclidinylbenzilate and the nicotinic antagonist alpha-bungarotoxin blocked the ACh action there might be a special, possibly mixed muscarinic/nicotinic ACh-receptor system in the myocytes of the bulbus cordis branchialis, which is different from the cholinergic receptor in the central part of the branchial heart.

M Gebauer

Papers

Inhibitory cholinergic effects on the autonomously contractile bulbus cordis branchialis of the cephalopod Sepia officinalis L.