Localization of tyrosine hydroxylase-like immunoreactivity in the nervous systems of Biomphalaria glabrata and Biomphalaria alexandrina, intermediate hosts for schistosomiasis.
Planorbid snails of the genus Biomphalaria are major intermediate hosts for the digenetic trematode parasite Schistosoma mansoni. Evidence suggests that levels of the neurotransmitter dopamine (DA) are reduced during the course of S. mansoni multiplication and transformation within the snail. This investigation used immunohistochemical methods to localize tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of catecholamines, in the nervous system of Biomphalaria. The two species examined, Biomphalaria glabrata and Biomphalaria alexandrina, are the major intermediate hosts for S. mansoni in sub-Saharan Africa, where more than 90% of global cases of human intestinal schistosomiasis occur. TH-like immunoreactive (THli) neurons were distributed throughout the central nervous system (CNS) and labeled fibers were present in all commissures, connectives, and nerves. Some asymmetries were observed, including a large distinctive neuron (LPeD1) in the pedal ganglion described previously in several pulmonates. The majority of TH-like immunoreactive neurons were detected in the peripheral nervous system (PNS), especially in lip and foot regions of the anterior integument. Independent observations supporting the dopaminergic phenotype of THli neurons included 1) block of LPeD1 synaptic signaling by the D2/3 antagonist sulpiride, and 2) the similar localization of aqueous aldehyde (FaGlu)-induced fluorescence. The distribution of THli neurons indicates that, as in other gastropods, dopamine functions as a sensory neurotransmitter and in the regulation of feeding and reproductive behaviors in Biomphalaria. It is hypothesized that infection could stimulate transmitter release from dopaminergic sensory neurons and that dopaminergic signaling could contribute to modifications of both host and parasite behavior.
Institute of Neurobiology and Department of Anatomy & Neurobiology, University of Puerto Rico, Medical Sciences Campus, San Juan, Puerto Rico, 00901.
Deborah
D
Vallejo
Mohamed R
MR
Habib
Nadia
N
Delgado
Lee O
LO
Vaasjo
Roger P
RP
Croll
Mark W
MW
Miller
D000818:Animals; D001700:Biomphalaria / Q000201:enzymology* / Q000469:parasitology / Q000502:physiology; D002395:Catecholamines / Q000378:metabolism; D002490:Central Nervous System / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D004396:Coloring Agents; D004298:Dopamine / Q000378:metabolism; D018492:Dopamine Antagonists / Q000494:pharmacology; D005557:Formaldehyde; D017952:Ganglia, Invertebrate / Q000166:cytology / Q000201:enzymology* / Q000502:physiology; D005976:Glutaral; D007150:Immunohistochemistry; D009474:Neurons / Q000187:drug effects / Q000201:enzymology* / Q000502:physiology; D017933:Peripheral Nervous System / Q000166:cytology / Q000201:enzymology / Q000502:physiology; D012550:Schistosoma mansoni; D013045:Species Specificity; D013469:Sulpiride / Q000494:pharmacology; D009435:Synaptic Transmission / Q000187:drug effects; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D002395:Catecholamines; D004396:Coloring Agents; D018492:Dopamine Antagonists; D005557:Formaldehyde; D013469:Sulpiride; D014446:Tyrosine 3-Monooxygenase; D005976:Glutaral; D004298:Dopamine
Schistosoma mansoni; dopamine; pond snail; pulmonate mollusk; trematode