A) SR-Lab Response software controls a solenoid switch (red arrows) which allows compressed air to flow through the odorant jar and into the startle chamber. When closed, clean air flows with no difference in airflow. Backflow is prevented by a series of one-way valves (yellow arrows). The odor is removed via an exhaust hose (green arrow) by outflow fan. Shock is generated by a programmable animal shocker and is delivered through the bars in the cage floor. During behavioral testing, startle is elicited by a 105 dB white noise burst. Activity and startle amplitude are measured by a piezoelectronic device beneath the floor of the cage. B) Cross-section of an olfactory bulb from a homecage mouse (top left - LacZ, top right, DAPI stain) or from an acetophenone + shock paired mouse (bottom left - LacZ, bottom right, DAPI stain). C) Medial and dorsal pairs of M71 glomeruli in X-gal stained olfactory bulbs from M71-IRES-tauLacZ mice. D) Glomerular surface area was larger in the acetophenone+shock trained group than in the homecage group (p<0.05). E) Glomerular cross-sectional area was larger in the acetophenone-trained vs the homecage mice, * p<0.05.

A) Glomerular cross-sectional area was larger in the acetophenone+shock group than either the acetophenone-alone or the homecage groups; * p<0.01 for acetophenone+shock vs homecage; * p<0.05 for acetophenone+shock vs acetophenone-alone. B) Mice learn an odor-shock association to both propanol and acetophenone and can discriminate between the two odors, p<.001. C) Glomerular cross-sectional areas were greater in the acetophenone+shock vs homecage, acetophenone-alone, and propanol-shock groups; * p<0.05 for each group vs acetophenone+shock.

A) Olfactory sensory neurons in the olfactory epithelium of an acetophenone+shock trained (top) and homecage mouse (bottom). B) More M71-LacZ+ olfactory sensory neurons were found in acetophenone-trained than homecage mice (p<0.05). C) Glomerular size is positively correlated with increasing olfactory sensory neuron number (triangles=home cage, squares=acetophenone+shock; Pearson's correlation coefficient=0.62, p<0.05).

A) Medial and dorsal M71 glomeruli in X-gal stained olfactory bulbs from acetophenone+shock paired mice trained over 3 consecutive days. B) Glomerular area was greater in the 3-days and 3-weeks acetophenone+shock trained vs the homecage mice, * p<0.05 vs homecage. C) M71 mice learned cocaine conditioned place preference (CPP) equally well with either no odor, or acetophenone paired with the cocaine, * p<0.05 vs pretrained. D) Glomerular area was greater in mice that were CPP-trained with acetophenone paired with cocaine, vs no odor paired with cocaine, * p<0.05).