Pharyngeal Neurons Research Articles

Two C. elegans genes control the programmed deaths of specific cells in the pharynx

The genes ces-1 and ces-2 control the decisions of two cells in the nematode Caenorhabditis elegans to undergo programmed cell death. Mutations that cause a gain of ces-1 function or a reduction of ces-2 function prevent these cells, the sisters of the two pharyngeal NSM neurons, from dying. These mutations do not affect most other cell deaths. Genetic studies indicate that ces-1 and ces-2 affect the fates of the NSM sisters by regulating the genes required for all programmed cell deaths to occur.

Pharyngeal pumping continues after laser killing of the pharyngeal nervous system of C. elegans

Using a laser microbeam to kill specific subsets of the pharyngeal nervous system of C. elegans, we found that feeding was accomplished by two separately controlled muscle motions, isthmus peristalsis and pumping. The single neuron M4 was necessary and sufficient for isthmus peristalsis. The MC neurons were necessary for normal stimulation of pumping in response to food, but pumping continued and was functional in MC- worms. The remaining 12 neuron types were also unnecessary for functional pumping. No operation we did, including destruction of the entire pharyngeal nervous system, abolished pumping altogether. When we killed all pharyngeal neurons except M4, the worms were viable and fertile, although retarded and starved. Since feeding is one of the few known essential actions controlled by the nervous system, we suggest that most of the C. elegans nervous system is dispensable in hermaphrodites under laboratory conditions. This may explain the ease with which nervous system mutants are isolated and handled in C. elegans.

A cell that dies during wild-type C. elegans development can function as a neuron in a ced-3 mutant.

Mutations in the C. elegans gene ced-3 prevent almost all programmed cell deaths, so that in a ced-3 mutant there are many extra cells. We show that the pharyngeal neuron M4 is essential for feeding in wild-type worms, but in a ced-3 mutant, one of the extra cells, probably MSpaaaaap (the sister of M4), can sometimes take over M4's function. The function of MSpaaaaap, unlike that of M4, is variable and subnormal. One possible explanation is that its fate, being hidden by death and not subject to selection, has drifted randomly during evolution. We suggest that such cells may play roles in the evolution of cell lineage analogous to those played by pseudogenes in the evolution of genomes.

The ecdysis of the cricket, teleogryllus oceanicus: Generation of the pharyngeal air-swallowing motor program by the isolated frontal ganglion

Abstract 1. 1. Air swallowed during the hour prior to rupture of the old cuticle of an ecdysing cricket produces sensory feedback which recruits abdominal peristaltic waves and other ecdysial motor programs. 2. 2. The frontal ganglion contains pharyngeal motor neurons, and produces rhythmical bursts from most of its nerves which are synchronous with swallowing movements and continue for up to an hour after the ganglion is isolated surgically and recorded in vitro. 3. 3. The frontal ganglion acquires this “activated state” with endogenous bursting during the period when air-swallowing is normally recruited.

Serotonin and octopamine in the nematode Caenorhabditis elegans.

The biogenic amines serotonin and octopamine are present in the nematode Caenorhabditis elegans. Serotonin, detected histochemically in whole mounts, is localized in two pharyngeal neurons that appear to be neurosecretory. Octopamine, identified radioenzymatically in crude extracts, probably is also localized in a few neurons. Exogenous serotonin and octopamine elicit specific and opposite behavioral responses in Caenorhabditis elegans, suggesting that these compounds function physiologically as antagonists.