Hillyer Lab News
Hillyer Lab News
Article on neurotransmitters and the mosquito heart is published in CBP-A
Friday, June 19, 2015
Insects employ an open circulatory system for the movement of hemolymph (insect blood) to all regions of the hemocoel (body cavity). The circulation of hemolymph is driven by several muscular pumps. The primary pump, called the dorsal vessel, is a tube-like structure that extends the length of the body along the dorsal midline. The region of the dorsal vessel that is situated in the thorax is called the aorta whereas the region that is situated in the abdomen is called the heart.
The insect heart contracts myogenically, as separation or disruption of neural input does not abolish heart contractions. However, multiple studies on a wide variety of insects have illustrated that the rhythmicity of heart contractions is at least partially modulated by neurohormones and neurotransmitters.
In this study we tested the effect of serotonin and glutamate on the heart contraction rate and the heart contraction directionality of the African malaria mosquito, Anopheles gambiae, and show that both of these neurotransmitters are cardioacceleratory.
Article citation:
Hillyer, J.F., T.Y. Estevez-Lao, and H.E. Mirzai. 2015. The neurotransmitters serotonin and glutamate accelerate the heart rate of the mosquito Anopheles gambiae. Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology. 188:49-57. (Pubmed) (See it in CBP-A) (Email me for a pdf copy)
Graphical abstract:
Article abstract:
Serotonin and glutamate are neurotransmitters that in insects are involved in diverse physiological processes. Both serotonin and glutamate have been shown to modulate the physiology of the dorsal vessel of some insects, yet until the present study, their activity in mosquitoes remained unknown. To test whether serotonin or glutamate regulate dorsal vessel physiology in the African malaria mosquito, Anopheles gambiae, live mosquitoes were restrained, and a video of the contracting heart (the abdominal portion of the dorsal vessel) was acquired. These adult female mosquitoes were then injected with various amounts of serotonin, glutamate, or a control vehicle solution, and additional videos were acquired at 2 and 10 min post-treatment. Comparison of the videos taken before and after treatment revealed that serotonin accelerates the frequency of heart contractions, with the cardioacceleration being significantly more pronounced when the wave-like contractions of cardiac muscle propagate in the anterograde direction (toward the head). Comparison of the videos taken before and after treatment with glutamate revealed that this molecule is also cardioacceleratory. However, unlike serotonin, the activity of glutamate does not depend on whether the contractions propagate in the anterograde or the retrograde (toward the posterior of the abdomen) directions. Serotonin or glutamate induces a minor change or no change in the percentage of contractions and the percentage of the time that the heart contracts in the anterograde or the retrograde directions. In summary, this study shows that the neurotransmitters serotonin and glutamate increase the heart contraction rate of mosquitoes.
According to the website of Comparative Biochemistry and Physiology - Part A: Molecular & Integrative Physiology, “This journal covers molecular, cellular, integrative, and ecological physiology. Topics include bioenergetics, circulation, development, excretion, ion regulation, endocrinology, neurobiology, nutrition, respiration, and thermal biology.”