MEMBRANE ELECTRICAL PROPERTIES AND SPIKE CHARACTERISTICS IN A PAIR OF IDENTIFIED ELECTRICALLY COUPLED <i>LYMNAEA STAGNALIS</i> NEURONS AT LONG-LASTING EXPERIMENTAL HYPERGLYCEMIA

Abstract

Microelectrode technique was used to study the responses of identified peptide-containing cells VD1 and RPaD2 within isolated CNS of Lymnaea stagnalis to long-lasting (not less 2 h) exposure in D-glucose (10 mM) containing solution. It has been established that electrical characteristics of RPaD2 membrane, compared to VD1, undergo significant changes under experimental hyperglycemia. Decrease of membrane resistance (Rm), accompanied by an increase of membrane capacitance (Cm) and time constant (τm), were observed. Despite the invariance of their firing rate, depolarization of VD1 membrane take place, while RPaD2 membrane potential did not vary significantly. Modifications in time-course, but not amplitude, of VD1 and RPaD2 action potentials were similar and resulted in increase of their main phases (rising, falling, undershoot) duration. It is assumed that “identity” in membrane electrical properties of Lymnaea’s CNS neurosecretory neurons (VD1/RPaD2) at hyperglycemia plays an adaptive role, aimed to overcome the possible desynchronization of their spike activity as a result of electrical decoupling, initiated by a high glucose content in intercellular space.