REGULATION OF ALPHA-7 NICOTINIC ACETYLCHOLINE-RECEPTORS IN MOUSE SOMATOSENSORY CORTEX FOLLOWING WHISKER REMOVAL AT BIRTH

Previous studies in postnatal mouse demonstrating high levels of alpha 7 nicotinic acetylcholine receptors on layer IV somatosensory cortica l neurons coincident with the onset of functional synaptic transmissio n led us to investigate whether the number and/or the localization of these receptors could be regulated by activity. Accordingly, we examin ed alpha-bungarotoxin binding in mouse somatosensory cortex following removal of all of the vibrissae on one side of the face, either by vib rissal follicle cauterization or daily plucking beginning on the day o f birth. Following vibrissa plucking, the levels of [I-125]alpha-bunga rotoxin binding on postnatal day 6 were significantly higher (23 +/- 7 %) in the denervated cortex (contralateral to the peripheral manipulat ion) than the intact cortex. Cauterization also resulted in significan tly higher (14 +/- 3%) [I-125]alpha-bungarotoxin binding in the contra lateral vs. the ipsilateral cortex. In contrast, there was no differen ce in [I-125]alpha-bungarotoxin binding in the left and right cortices of unoperated control animals. At postnatal day 14, levels of [I-125] alpha-bungarotoxin binding in layer IV were very low in control animal s as well as in animals subjected to whisker plucking or cautery. Thes e findings suggest that reducing activity in the somatosensory pathway regulates the density of alpha 7 nicotinic acetylcholine receptors du ring the first postnatal week. However, the normal decrease in recepto r density that is seen during the second postnatal week of development proceeds despite altered sensory activity. (C) 1998 Wiley-Liss, Inc.