AIML, AIMR

Type: Interneuron
Connectivity:
- In MoW: AIM
- In WormWiring: AIMLh, AIMRh, AIMLm, AIMRm
- In Nemanode: AIM
In Wormbase: AIM, AIML, AIMR
Lineage: AB plpaapppa, AB prpaapppa
Location: Ventral ganglion in the head
Description: Ring interneurons bridging sensory inputs and command outputs. Excessive neurites that connect AIML and AIMR early in development are pruned during larval stages (along with RIF, they are the only other neuron pair that is subject to developmental neurite pruning in C. elegans) (Hayashi et al., 2009; Kage et al., 2005). The process of each AIM neuron enters the nerve ring from the ventral side. After running dorsally within the nerve ring, it meets its contralateral partner at the dorsal midline and makes a gap junction with it.
Neurotransmitter/ Neuropeptide:
- Acetylcholine - only in males after L4
- Glutamate - sexually dimorphic expression; in hermaphrodites AIMs are glutamatergic and serotonergic. In males, they are glutamatergic and serotonergic until L3. During L4 they become cholinergic and serotonergic
- Serotonin - may be absorbing and then releasing rather than synthesizing serotonin
- FLP-10; FMRFamide-like peptide
- FLP-22; FMRFamide-like peptide
- INS-1; insulin-like peptide
- PDF-1; pigment dispensing factor homolog
(Pereira et al., 2015; Barrios et al, 2012; Loer and Rand, 2022; Li and Kim, 2008; Sze et al., 2000; Duerr et al., 1999)

Innexin expression:
- CHE-7 (only in dauer)
- INX-2
- INX-7
- INX-10a
- INX-14
- INX-19
- UNC-9
(Altun et al., 2009; Bhattacharya et al., 2019)
Receptor expression:
- GCY-18; guanylate cyclase
(Wormbase; Ortiz et al., 2006)
Function: Serotonin secreted by both synaptic vesicles and dense core vesicles seem to diffuse readily to the extrasynaptic space adjacent to the AIM and RIH neurons. Among 5 classes (NSM, ADF, HSN, AIM, RIH) of serotonergic neurons, RIH and AIM mainly take up serotonin from outside (produced by the remaining serotonergic neurons) via the membrane serotonin transporter (MOD-5/SERT), rather than synthesizing it themselves (Jafari et al., 211).
- RIH and AIM possibly function as temporal–spatial regulators of extrasynaptic serotonin to modulate the activity of the behavioral circuits. In Caenorhabditis elegans, serotonin signaling is required for coupling feeding and the memory of prior food availability to the rate of locomotion. Following food deprivation, wild-type animals show markedly decreased locomotion on their return to a lawn of bacterial food. While serotonin-deficient mutants exhibit less slowing response (become insensitive), mutants of mod-5/SERT exaggerate the slowing response (become hypersensitive). Transgenic expression of mod-5/SERT in the serotonin-absorbing neurons fully corrects this exaggerated behavior, suggesting AIM and RIH regulate the availability of serotonin for neurotransmission (Jafari et al., 2011).
- Function in swim initiation; behaviorally, ablation of VC-4, VC-5, AIM, or NSM neurons delays swim onset, implicating serotonin signaling in this behavior (Vidal-Gadea et al., 2011)
- They are part of the neuronal circuit that functions in mate-searching behavior of males (Barrios et al, 2012)
Reporters:
- At CGC: OH12503 otIs520 [eat-4(prom11)::GFP + ttx-3::mCherry] X. AIM is marked only with GFP, not mCherry. Can be used to isolate AIM by FACS. Used by CeNGEN project for RNA-Seq cengen.org.
- Other:
IDENTIFICATION:
The three neurons, AIM, AIY and AVK resemble pearls-on-a-string, located posterior and slightly more superficial to the excretory cell nucleus on the right and left sides of the head. The nucleus of the excretory cell is the biggest one on the ventral side, below the terminal bulb of the pharynx and looks like an egg with a sunny-side-up appearance. The three neuronal nuclei can easily be located immediately posterior to the excretory cell nucleus, the most anterior one being AIM, the middle, AIY, and the most posterior one, AVK. On the right side, sometimes RIS nucleus accompanies these three nuclei. Cell and axon structures of AIY and AIM are very similar; care must be taken to differentiate between the two when identifying these two cells with fluorescent markers.

Click image for closeup view Click pictures for higher resolution image
 
 

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AIML (AB plpaapppa) development in the embryo. Dorsal view. Bottom is left side of the embryo. Spheres indicate individual nuclei. Black sphere: ancestors of AIML; dark grey spheres: apoptotic cells; other cells follow the WA color code (after they acquire specific cell or tissue identities). 0 min is fertilization. Click on the movie for higher resolution rendition (by A. Santella & Z. Bao).
 
 

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AIMR (AB prpaapppa) development in the embryo. Dorsal view. Bottom is left side of the embryo. Spheres indicate individual nuclei. Black sphere: ancestors of AIMR; dark grey spheres: apoptotic cells; other cells follow the WA color code (after they acquire specific cell or tissue identities). 0 min is fertilization. Click on the movie for higher resolution rendition (by A. Santella & Z. Bao).


Last revision: April 24,2024
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