Effects of compounds related to beta-hydroxyglutamic acid (BHGA) on identifiable giant neurones of an African giant snail (Achatina fulica Férussac).

The present study aimed to further elucidate the pharmacological features, with respect to sensitivity to L-BHGA agonists, of the receptors sensitive to beta-hydroxy-L-glutamic acid (L-BHGA) in five Achatina giant neurones: PON (periodically oscillating neurone), d-RPLN (dorsal-right parietal large neurone), VIN (visceral intermittently firing neurone), RAPN (right anterior pallial neurone) and v-RCDN (ventral-right cerebral distinct neurone). Of these neurones, d-RPLN and RAPN were depolarized by L-BHGA, while PON, VIN and v-RCDN were inhibited. Threo-beta-hydroxy-DL-aspartic acid markedly depolarized d-RPLN and RAPN (effective potency quotient (EPQ) in relation to the more effective L-BHGA isomer: 1 for d-RPLN and 0.3 for RAPN). This compound produced only slight inhibitory effects on PON, VIN and v-RCDN with EPQs calculated to be less than 0.03, less than 0.03 and 0.03, respectively. On the other hand, erythro-beta-hydroxy-DL-aspartic acid at 10(-3) M was almost ineffective, except on v-RCDN where it elicited some slight inhibitory effects (EPQ: 0.01). L-Aspartic and D-aspartic acid at 10(-3) M, also had almost no effect except for slight effects of D-aspartic acid on d-RPLN (EPQ: 0.1). N-Methyl-L- and N-methyl-D-aspartic acid were slightly effective only on v-RCDN (EPQ: less than 0.01 and 0.01, respectively). The other compounds, including beta-hydroxypyrroglutamic acid (cyclic BHGA) and proline derivatives, were almost ineffective at 10(-3) M; very weak effects were occasionally observed on some neurones.(ABSTRACT TRUNCATED AT 250 WORDS)