Amanda Celii

The development of in ovo odor sensitivity in chicks

The chick olfactory system in the embryo is known to attain function prior to hatching; the periphery neurons develop function as early as embryonic day 13 (E13). To determine the specificity and critical period for development of odor sensitivity in chick olfactory central nervous system, the different patterns of activation of the immediate early gene cFos in the olfactory bulb were determined. Chick embryos were exposed to amyl acetate, phenylethyl alcohol, or no odor for 3 day periods from E14 through E20;  cFos immunoreactivity was examined to determine olfactory bulb activation as a result of odorant exposure. Staining patterns for each animal exposed to amyl acetate versus phenylethyl alcohol and those from chicks exposed to the same odorant over different time periods were compared. cFos staining patterns suggest differences in odorant-elicited bulbar activation occur from E15 through E18 suggesting that the critical period for the development of odor sensitivity occurs at this time. This highlights the importance of the sensory environment in shaping the developmental pathways of the olfactory system.

Sol de Jesus

Behavioral observation of odor imprinting in chicks

The chick olfactory system begins development at embryonic day 8 (E8) and is known to be functional by E15.   Studies have shown that chick embryos exposed to odorants in ovo can recognize these odorants after hatching, suggesting that the olfactory system perceives and decodes odor stimuli during development.  This in ovo experience, imprinting, may shape the animals’ behavior upon hatching, presumably to make them better adapted to their immediate surroundings.  Much like visual imprinting, “odor imprinting” may impart a survival advantage to newborn chicks.  The present study attempts to investigate when odor imprinting occurs during embryonic development.  The incubated chicks were exposed to single odorant for 3-day periods from E12 and E21.  Upon hatching and two days after birth, chicks were tested for their preference for “familiar” versus “unfamiliar” odorants using a T-maze.  Unlike previous studies, both a novel odorant, phenylethyl alcohol and amyl acetate, were introduced to determine if exposure to odors in ovo early on could induce behavioral preferences in newborn chicks and an attempt to quantify the timeline of the development of this chemical sensitivity to imprinting were conducted.  Incubated chick eggs were exposed to single odorant for 3-day period intervals from E12 and E21.  Result showed that although imprinting did not occur odor recognition of amyl acetate did take place.  The chicks did not detect Phenylethyl alcohol suggesting avoidance.  An induced sensitivity could not be proven for the odorants, which suggest preference over imprinting. 

James Costanzo

The Na⁺/Ca²⁺ exchanger is not the primary mechanism for odorant-elicited calcium decreases in cultured human olfactory cells

Olfactory receptor neurons (ORNs) respond to odorants with changes in intracellular calcium concentrations ([Ca²⁺]). In human ORNs, about a fourth of these responses are decreases in [Ca²⁺]; thus this type of response represents a large portion of the input into the olfactory bulb, yet the mechanism behind this type of response is unknown. The involvement of the Na⁺/Ca²⁺ exchanger (NCX) was investigated in this system using human olfactory cultured cells (HOCCs) due to their availability, ease of use, and because they demonstrate structural and functional characteristics similar to those found in acutely isolated human ORNs. Cells were grown on 6-well plates and tested with odorants in the presence or absence of extracellular Na+; responses were measured using calcium-imaging techniques. The cells were subsequently fixed and tested with immunocytochemistry using antibodies against the NCX. This study suggests that the NCX is present in HOCCs but is not the primary mechanism for mediating odorant-elicited [Ca²⁺] decreases. An understanding of the mechanism responsible for generating [Ca²⁺] changes may have important implications for the study of the physiology of olfaction, neural development, and neurodegenerative diseases.

Stephanie Yazinski

Correlation of structural and functional maturation of olfactory receptor neurons

Human olfactory receptor neurons have the unique ability to regenerate in a short time span (about 7 days), which are of interest because of the possible applications including understanding of neurogenesis, regeneration and repair of the olfactory system, as well as, possible stimulation of growth of non-olfactory neural tissue.  The present study attempts to correlate structural and functional maturation of olfactory receptor neurons (ORNs) using immunocytochemistry and fluorescence imaging of changes in odorant-elicited intracellular Ca²⁺ concentration.  Unlike previous studies, both the morphologically distinct, phase bright ORNs, and phase dark, “glial-like” cells, were tested for odorant-elicited responses and immunocytochemical staining.  Results showed that many of these different cell types all respond to odorants but do not express the marker proteins associated with ORNs, indicating that these other non ORNs may also participate in the overall odorant response.  These cells may be immature neurons, which respond nonspecifically to odorants, or supporting glial cells which exhibit nonspecific odorant-elicited or high potassium elicited responses.  Thus, the development of functional attributes may be independent from structural maturation.