[Action of carbacyclic 13,14-didehydro-analogs of prostacyclin on the contractile activity of the rat stomach muscles]. / Deistvie karbitsiklicheskikh 13,14-didegidro-ananlogov prostatsiklina na sokratitel'nuiu aktivnost' myshtsy zheludka krysy.

The pharmacological activity of bicyclooctane and bicycloheptane analogues of prostacyclin was studied on the rat stomach muscle strip. All the analogues are partial agonists. EC50 of the most active of them, 5E isomer of bicyclooctane analogue, is 2.8.10(-7) M-1.2.10(-7) M. 5E isomers of both bicyclooctane and bicycloheptane analogues with a normal length of alpha-chain are at least by an order of values more active than the corresponding 5Z isomers. At the increase of alpha-chain by one methylene group the activity of 5E and 5Z isomers of bicycloheptane analogue becomes similar.

Cholinoreceptors of the dentis retractor muscle of the sea urchin Strongylocentrotus intermedius.

Neostigmine increases and cholinergic blocking agents block contractions of Strongylocentrotus intermedius dentis retractor muscle caused by either acetylcholine or indirect stimulation. Both innervated and non-innervated parts of the muscle are sensitive to low acetylcholine concentration suggesting that there are both synaptic and extra-synaptic cholinoreceptors. Nicotinomimetics are more potent than muscarinomimetics. Both d-tubocurarine and atropine are weak blocking agents as compared to pentadecamethylene-bis-trimethylammonium or hexadecamethylene-bis-trimethylammonium, Kd being 1 X 10(-4) to 5 X 10(-5) and 5 X 10(-7) to 4 X 10(-7) M respectively. Disulphide bonds and carboxylic (or phosphate) groups were revealed in dentis retractor muscle cholinoreceptors using drugs modifying receptor structure. Cholinoreceptors of both nicotinic and muscarinic type were revealed in oesophagus longitudinal muscles of Strongylocentrotus intermedius.

The muscle chemoreceptors of the ascidian Halocynthia aurantium.

The body wall muscle of the ascidian, Halocynthia aurantium, is sensitive to both nicotinomimetics and muscarinomimetics. Atropine (4 X 10(-11 M) and benzilylcholine mustard (1 X 10(-5) M for 15 min) selectively block responses to muscarinomimetics. d-Tubocurarine (2 X 10(-6) M) and hexadecamethylene-bis-trimethylammonium (2 X 10(-7) M) prevent contractions induced by both nicotinomimetics and muscarinomimetics. In the cold season of the year the sensitivity of the muscle to muscarinomimetics disappears while responses to nicotinomimetics do not change throughout the year. The cooling of the water in the experimental bath results in an increase in the muscle contractions caused by muscarinomimetics while the responses to nicotinomimetic propionylcholine do not change. Catecholamines induce a decrease of the ascidian muscle responses to acetylcholine, cGMP and papaverine produce a similar effect.

[Pharmacologic analysis of the biphasic postsynaptic potentials of an identified neuron of the mollusk Planorbarius corneus]. / Farmakologicheskii analiz dvukhfaznykh postsinapticheskikh potentsialov identifitsirovannogo neirona molliuska Planorbarius corneus.

Identified neuron in the left pedal ganglion of the mollusc P. corneus responds by biphasic postsynaptic potential (BPSP) to nerve stimulation. The depolarizing phase of both the BPSP and the response to acetylcholine is abolished by tubocurarine, whereas the hypopolarizing phase is blocked by tetramethylammonium. The results obtained suggest that BPSP is due to activation of two kinds of cholinoreceptors in the neuronal membrane.

[Hyperpolarization response of an identified neuron of Planobarius corneus mollusks to several cholinomimetic substances]. / Giperpoliarizatsionnyi otvet identifitsirovannogo neirona molliuska Planorbarius corneus na nekotorye kholinomimeticheskie veshchestva

Two kinds of responses to cholinomimetics were found on the identified neuron (P-2) of Planorbarius corneus pedal ganglion using microelectrode technique. Nicotinomimetics caused depolization whereas some muscarinomimetics caused hyperpolarization of the neuron membrane. Acetylcholine usually depolarized the neuron membrane but after the blockade of nicotinic receptors with tubocurarine one can reveal a hyperpolarizing action of acetylcholine. These findings suggest that two kinds of receptors exist on the P-2 neuron membrane and these receptors differ both in pharmacological characteristics and in ionic permeability changes they control.