Type: Interneuron
In MoW: RIA
Male Wiring Project: RIAL, RIAR
In Wormbase: RIA, RIAL, RIAR
Lineage: AB alapaapaa, AB alaapppaa
Location: Head
Description: These neurons receive synaptic inputs from AIY and AIZ interneurons and densely innervate head motor neurons SMD and RMD
Neurotransmitter/ Neuropeptide:
- Glutamate
(Pereira et al., 2015)
Innexin expression: Although MoW shows no gap junctions for RIA neurons, and no innexin expression has yet been detected in RIA neurons in the hermaphrodite, the Wormwiring Project shows both hermaphrodite RIAL/RIAR and male RIAL/RIAR make gap junctions
Receptor expression:
- SER-1 serotonin receptor
(Dernovici et al, 2007; Carnell et al, 2005)
Function: RIM, RIA and RIB are classified as the

"second layer" interneurons in the process of integration of information from the outside world and the inner state of the animal, which then leads to a behavioral response.
- Function in thermotaxis: Along with AIY and AIZ, RIA are thermotaxis core interneurons. A mutation that impairs the function RIA neurons or laser ablation of RIA causes athermotactic or cryophilic behavior. Killing RIA neurons has no effect on chemotaxis (Iino and Yoshida, 2009; Tanizawa et al., 2006; Mori and Ohshima 1995). In the original two-drive (thermophilic vs cryophilic) model of thermotaxis, RIA is suggested to integrate signals processed in the thermotaxis neural circuit and emit outputs to downstream neurons (Mori and Ohshima, 1995; Tanizawa et al, 2006). Multiple signals including EAT-4-dependent glutamatergic neurotransmission from RIA are involved in communicating processed information to downstream neurons, thereby generating ultimate thermotactic outputs (Ohnishi et al, 2011). Although it is not clear as to which neurons downstream of RIA are main component neurons in the circuit, RIA is heavily connected presynaptically to SMD or RMD head motor neurons that regulate turning behavior, suggesting SMD and RMD control turn frequency and run duration depending on the thermal information transmitted by RIA (Ohnishi et al, 2011; Zariwala et al, 2003; White et al, 1986; Gray et al, 2005)
- Function in locomotion: Killing RIA slightly decreases reversals during local search and dispersal (Gray et al., 2005)