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Relationship between latency and period for 5-hydroxytryptamine-induced membrane responses in the Calliphora salivary gland.

ABSTRACT: Following stimulation with a calcium-mobilizing agonist there is often a distinct latency (L) preceding the onset of the first calcium spike. In the continued presence of the agonist, repetitive spikes appear separated by a variable period (P). The relationship between L and P has been investigated in an insect salivary gland responding to 5-hydroxytryptamine (5-HT). Both L and P were found to decrease as the concentration of 5-HT was increased over its physiological range of 1-10 nM. Lowering the concentration of external calcium from 1 x 10(-3) M to 1 x 10(-5) M increased both P and L. However, the effect on L was apparent only at low levels of 5-HT. Reducing the content of the internal stores by repeated stimulation in a calcium-free medium resulted in a progressive prolongation of L. On the other hand, the effect of L decreased when glands were stimulated repetitively in normal calcium-containing medium. All these results are consistent with a hypothesis that calcium plays a critical role in determining the kinetics of calcium release during both L and P. An important component seems to be the entry of external calcium, which sets the stage for calcium release by loading up the internal stores. As these stores fill up with calcium, the Ins(1,4,5)P3 receptors will initiate a calcium spike once they become sensitized to the ambient level of Ins(1,4,5)P3.

SUBMITTER: Berridge MJ

PROVIDER: S-EPMC1137262 | biostudies-other | 1994 Sep

REPOSITORIES: biostudies-other

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Project description:Mosquito-borne diseases are major health problems worldwide. Serological responses to mosquito saliva proteins may be useful in estimating individual exposure to bites from mosquitoes transmitting these diseases. However, the relationships between the levels of these IgG responses and mosquito density as well as IgG response specificity at the genus and/or species level need to be clarified prior to develop new immunological markers to assess human/vector contact. To this end, a kinetic study of antibody levels against several mosquito salivary gland extracts from southeastern French individuals living in three areas with distinct ecological environments and, by implication, distinct Aedes caspius mosquito densities were compared using ELISA. A positive association was observed between the average levels of IgG responses against Ae. caspius salivary gland extracts and spatial Ae. caspius densities. Additionally, the average level of IgG responses increased significantly during the peak exposure to Ae. caspius at each site and returned to baseline four months later, suggesting short-lived IgG responses. The species-specificity of IgG antibody responses was determined by testing antibody responses to salivary gland extracts from Cx. pipiens, a mosquito that is present at these three sites at different density levels, and from two other Aedes species not present in the study area (Ae. aegypti and Ae. albopictus). The IgG responses observed against these mosquito salivary gland extracts contrasted with those observed against Ae. caspius salivary gland extracts, supporting the existence of species-specific serological responses. By considering different populations and densities of mosquitoes linked to environmental factors, this study shows, for the first time, that specific IgG antibody responses against Ae. caspius salivary gland extracts may be related to the seasonal and geographical variations in Ae. caspius density. Characterisation of such immunological-markers may allow the evaluation of the effectiveness of vector-control strategies or estimation of the risk of vector-borne disease transmission.

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Relationship between latency and period for 5-hydroxytryptamine-induced membrane responses in the Calliphora salivary gland.

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