Type: Sensory neuron (mechanosensory)
In MoW: PLM
Male Wiring Project: PLML, PLMR
In Wormbase: PLM, PLML, PLMR
Lineage: AB plapappppaa, AB prapappppaa
Location: Lumbar ganglia
Description: Posterior lateral microtubule cells, aka touch receptor neurons. Send ventrally directed processes to ventral cord.
Neurotransmitter/Neuropeptide:
- Glutamate
(Lee et al., 1999)
Innexin expression:
- INX-7
- INX-13
- UNC-9
(Altun et al., 2009)
Receptor expression:
- DEG-3; alpha subunit of nicotinic acetylcholine receptor
- DES-2; alpha subunit of nicotinic acetylcholine receptor
- DOP-1; D1-like dopamine receptor
- GLR-8; ionotropic glutamate receptor subunit (unclassifiable as NMDA or non-NMDA)
- MEC-2; stomatin-like protein required to sense touch, part of a mechanotransduction channel complex that senses low-threshold stimuli (gentle body touch)

- MEC-4; mechanically gated ion channel subunit; amiloride-sensitive Na⁺ channel (ASC) protein (DEG/ENaC subunit). - part of a mechanosensory transduction channel - core component of a mechanosensory transduction channel that senses low-threshold stimuli (gentle body touch)
- MEC-6; part of the degenerin/epithelial Na⁺channel complex - interacts physically with the MEC-4 degenerin ion channel
- MEC-9; provides an extracellular attachment point for the mechanosensory channels in touch cells
- PDFR-1; pigment dispersing factor (PDF-1) receptor
(Wormbase; Barrios et al., 2012; Sanyal et al., 2004; Chelur et al., 2002; Brockie et al., 2001; Treinin. et al., 1998; Du et al., 1996; Lai et al., 1996; Huang et al., 1995; Treinin and Chalfie, 1995)
Function:
- Along with AVM and ALM, PLM neurons sense gentle (low threshold) mechanical stimulus to the body and provide input to the command (inter) neurons (PVC, AVB, AVD, AVA) via both synaptic connections and gap junctions (see mechanosensory circuit in C.elegans Book II and circuit for escape response in Pirri and Alkema, 2011). The touch cells form gap junctions with agonist interneurons and chemical synapses with the antagonist interneurons (see locomotory circuit). Hence, in the neural circuit of the escape response, the posterior touch cells PLML/R form gap junctions with the forward movement interneuron PVC, but they provide synaptic input to the backward movement interneurons AVA and AVD (Goodman, 2006; Chalfie et al.,1985; Kaplan and Driscoll, 1997)
- Along with other TRNs, PLM neurons are involved in memory formation for habituation to tap response both for massed training with 12-hr memory retention and spaced training with 48-hr memory retention (Li et al., 2013). Long-term memory for tap habituation requires protein synthesis, the transcription factor CREB and the AMPA-type glutamate receptor subunit GLR-1 in the postsynaptic AVA and AVD interneurons of the tap withdrawal circuit, while 12-hr memory is correlated with a FLP-20-dependent increase of synaptic vesicles in the terminals of the PLM mechanosensory neurons and likely other TRNs (Timbers and Rankin, 2011; Li et al., 2013)