Mechanosensory Stimuli Research Articles

Processing of chemosensory and mechanosensory information in identifiable Aplysia neurons

1. 1. The chemosensory and mechanosensory pathways from the anterior tentacles of Aplysia californica were examined. 2. 2. The responses of central neurons to both modalities persisted after blocking synaptic transmission in the tentacles, suggesting that the first order synapses are located in the CNS. 3. 3. Mechano- and chemosensory input to the cerebral ganglion B neurons remained after blocking polysynaptic pathways indicating that they are second order neurons for both modalities. 4. 4. The two modalities are distinguished by the B neurons in that mechanosensory input caused essentially phasic excitation while chemosensory responses elicited by food chemicals produced more tonic and long lasting firing. 5. 5. Although the third-order neurons have yet to be identified, evidence is presented that the cerebral ganglion A cluster neurons are fourth-order in both mechano- and chemosensory pathways. 6. 6. A neuron responses to tactile stimuli were usually hyperpolarizing and began approximately 200 msec after the onset of the B neuron response. In contrast, food chemosensory and strong mechanosensory (water currents) stimuli often elicited A neuron firing. The mechanisms involved in mediating the different A neuron responses are considered.