[Effect of excitant amino acid antagonists on glutamate receptors in the locust and on convulsions induced by glutamate, aspartate, kynurenine and quinolinic acid in mice]. / Vliianie antagonistov vozbuzhdaiushchikh aminokislot na glutamatnye retseptory saranchi i sudorogi, vyzvannye glutamatom, aspartatom, kinureninom i khinolinovoi kislotoi na myshakh.

All excitatory amino acid antagonists studied: diethyl esters of aspartic (DEEA) and glutamic (DEEG) acids, 2-amino-3-phosphono-propionic acid (APPA) and 2-amino-4-phosphono-butanoic acid (APBA), diminished the amplitude of excitatory postsynaptic potentials (EPP) of the locust (Locusta migratoria migratorioides) muscle fibers and arbitrary blocked glutamate (GLU) and aspartate (ASP) responses. Kynurenine (KYN) and quinolinic (QUI) acid had no effect on EPP even at a concentration of 2 X 10(-2) M. The antagonists were not strictly selective against intracerebroventricularly administered endogenous convulsants: GLU, ASP, KYN and QUI and in simulation of experimental seizures in mice. The antagonists structurally similar to ASP prevented ASP- and KYN-induced seizures in lower doses than GLU derivatives. Anti-KYN, but not anti-QUI DEEA, DEEG, APPA and APBA efficacy suggests that KYN and QUI act on different structures or binding sites.

[Miniature potentials in fast and slow muscle fibers in the locust]. / Miniatiurnye potentsialy v bystrykh i medlennykh myshechnykh saranchi.

The miniature excitatory postsynaptic potentials were studied in the fast and slow fibres of Locusta migratoria by means of intracellular microelectrodes. Statistical analysis indicated that the spontaneous transmitter release can be predicted by the negative binomial formula with a 85% reliability. It shows that there is certain mutual interaction between the processes responsible for the spontaneous release of the transmitter from locust nerve terminals. In the calcium-free solutions frequency of miniature potentials was reduced to about 83.5% in the fast muscle fibres and to about 96.3% in the slow muscle fibres. A study of Mg++ effect on frequency of miniature potentials showed that 10 mM Mg++ reduced the frequency to about 75% in the fast muscle fibres and to about 90% in the slow ones. The conclusion is drawn that in the fast and slow muscle fibres the nerve terminals possess different sensitivity to the changes in ionic composition of the environment.

[Ionic conductivity of muscle fiber membranes of Locusta migratoria]. / Ionnaia provodimost' membrany myshechnykh volokon saranchi Locusta migratoria.

On muscle fibers from m. flexor tibiae of the locust studies have been made of the effect of rapid changes in potassium and chloride concentrations on the membrane potential (MP). The MP constituted 56.0 +/- 1.0 mV. The relationship between the MP and the external potassium at [K]o.[Cl]o equals const may be described by Nernst equation for two different intracellular concentrations of these ions, at [K]o less than or equal to 40 mM and at [K]o greater than or equal to 80 mM. From the relationship between the MP and rapid changes in [K]o or [Cl]o at constant concentration of correspondingly [Cl]o and K]o relative membrane conductivity for these ions were found (TK=0.55 and TC1=0.41). Using impulse analysis, electrical constants of muscle membrane were determined (lambda = 1.9 +/- 0.1 mm; Ri equals 103 +/- 7 ohm.cm; Rm = 1.430 +/- 76 ohm.cm2; Cm = 16 +/- 1 muF.cm-2). High values for Cm correlate with numerous invaginations in muscle membrane which were revealed in electron microscopis investigations. Active responses of the membrane are gradual. In the presence of ions of Sr they are transformed into regenerative action potentials.

[Functional features of the locomotor muscles of the locust]. / Funktsional'nye osobennosti lokomotornykh myshts saranchi.

The ultrastructure of muscle fibres, membrane electrical constants and synaptic membrane responses to microapplication of l-glutamate were investigated in longitudinal flight muscle and flexor tibia of Locusta migratoria migratorioides. The sarcomers of the flight muscle (fast) were smaller then those of the leg muscle (slow). The effective resistances (Ro) of the flight and leg muscles were (2.25 +/- 0.54)-10(5) omega and (1.65 +/- 0.57) X 10(5) omega. The specific resistance (Rm), space constant (tau) and time constant (lambda) in the same muscles were 774 +/- 106 omega-cm and 2583 +/- 119 omega-cm-2; 7.3 +/- 1.7 ms and 17.5 +/- 1.1 ms; 093 +/- 0.22 mm and 1.98 +/- 0.42 mm. When l-glutamate was applied iontophoretically to muscle fibres depolarization was recorded only in localized parts of the membrane. Microapplication of acetylcholine to intact and denervated muscle fibres of the slow leg muscle was uneffective. It is suggested that l-glutamic acid is the excitatory transmitter both in slow and fast insect muscles.