Effects of four stereoisomers of beta-hydroxyglutamic acid on identifiable giant neurons of an African giant snail (Achatina fulica Férussac).

The effects of four stereoisomers of beta-hydroxyglutamic acid (erythro-L-BHGA, threo-L-BHGA, erythro-D-BHGA and threo-D-BHGA) and glutamic acid (L-Glu and D-Glu) were compared on six identifiable giant neurons of Achatina fulica Férussac, namely, PON (periodically oscillating neuron), VIN (visceral intermittently firing neuron), d-RPLN (dorsal-right parietal large neuron), RAPN (right anterior pallial neuron), FAN (frequently autoactive neuron) and v-RCDN (ventral-right cerebral distinct neuron). On PON and VIN, erythro-L-BHGA was the most inhibitory (effective potency quotient (EPQ) of the substance: 1.0). Its minimum effective concentration (MEC) for both neurons was the same at 3 X 10(-5) M. The effect of threo-L-BHGA was weaker (EPQ in relation to the most effective substance: 0.3-0.1). Erythro- and threo-D-BHGAs were almost ineffective on PON (EPQ: less than 0.03) though they had some effects on VIN (EPQ: 0.1-0.03 for erythro-D-BHGA and 0.3-0.1 for threo-D-BHGA). On d-RPLN, erythro-L-BHGA was the most excitatory (MEC: 10(-4)M). Threo-L-BHGA and threo-D-BHGA also had some effects (EPQ: 0.1 and 0.3 respectively), while erythro-D-BHGA was ineffective. On RAPN, erythro- and threo-L-BHGAs were the most excitatory (MEC: 10(-4) M). Threo-D-BHGA was also excitatory (EPQ: 0.3), while erythro-D-BHGA was ineffective. Threo-L-BHGA was the most inhibitory on FAN and v-RCDN (MEC: 10(-4) M in FAN and 10(-5) M in v-RCDN).(ABSTRACT TRUNCATED AT 250 WORDS)