Integral part of various neural sensory systems in the antenna that provide the neural basis for the response to environmental changes in temperature (thermosensation), humidity (hygrosensation) and odor detection (PubMed:21220098, PubMed:27161501, PubMed:27656904). Required for odor-evoked electrophysiological responses in multiple neuron classes in the antenna and is likely to function as part of an olfactory receptor complex with Ir76a and Ir76b (PubMed:21220098). Together with Ir21a and Ir93a, mediates the response of the larval dorsal organ cool cells, a trio of cool-responsive neurons, to cooling and is required for cool avoidance behavior (PubMed:27126188, PubMed:27161501, PubMed:27656904). Required in chordonotal organ neurons for behavioral synchronization to low-amplitude temperature cycles and mediates circadian clock resetting by temperature (PubMed:26580016). Together with Ir40a and Ir93a, mediates the response of the hydrosensory sacculus neurons to changes in relative humidity, and is required for dry detection and humidiy preference behavior (PubMed:27161501, PubMed:27656904). Interacts with nocte. Low levels detected in the axon segment adjacent to the perikaryon in some sensory neurons of the antenna but not detected along axons as they enter the brain or at synapses within antennal lobe glomeruli. In coeloconic neurons, prominently expressed both in the perikaryon and in the distal tip of the dendrite which corresponds to the ciliated outer dendritic segment innervating the sensory hair. Relatively low levels detected in inner dendrites (PubMed:19135896). Detected in dendritic bulbs of the dorsal organ cool cells (PubMed:27126188). In the antenna, detected in neurons of the arista and also detected in sacculus neurons which innervate the first and second chambers (at protein level) (PubMed:21220098, PubMed:19135896, PubMed:27656904). Throughout the main body of the antenna, expressed in neurons which innervate the coeloconic class of olfactory sensilla (at protein level) (PubMed:21220098, PubMed:19135896). Expressed in multiple cells of the dorsal organ including the dorsal organ cool cells (at protein level) (PubMed:27126188, PubMed:27656904). Detected in femur and retina (PubMed:26580016). Expressed in a subset of femur chordonotal neurons and antennal Johnston's Organ neurons (PubMed:26580016). No visible phenotype (PubMed:21220098). Viable and fertile but their response to environmental cues such as temperature, humidity and odorants is impaired (PubMed:21220098, PubMed:26580016, PubMed:27126188, PubMed:27161501, PubMed:27656904). Response of ac4 coeloconic sensilla neurons to agonist phenylethylamine and of ac2 sensilla neurons to agonist 1,4-diaminobutane is abolished (PubMed:21220098). Response of dorsal organ cool cells to changes in temperature is abolished and consequently larvae fail to avoid cool temperatures (PubMed:27126188, PubMed:27161501, PubMed:27656904). Response of sacculus neurons to changes in humidity is also abolished and consequently larvae fail to move towards their preferred humidity (PubMed:27161501, PubMed:27656904). Failure to synchronize in constant light or constant dark to shallow temperature cycles with an amplitude of 2 degrees Celsius (PubMed:26580016). In constant light, mutants display constant activity throughout the temperature cycle in contrast to controls which show a clear activity peak in the second part of the warm period before and after a 6 hour shift of the temperature cycle (PubMed:26580016). In constant dark, mutants do not shift their evening peak during the temperature cycle in contrast to controls which advance or delay their evening activity peak during phase-advanced or phase-delayed temperature cycles (PubMed:26580016). Barely detectable levels of circadian rhythm protein tim in dorsal neurons DN1 and DN2 (PubMed:26580016). RNAi-mediated knockdown in chordonotal neurons disrupts synchronization of locomotor activity rhythms with temperature cycles (PubMed:26580016). Belongs to the glutamate-gated ion channel (TC 1.A.10.1) family.