RESPONSES OF SINGLE UNITS IN 6TH LUMBAR DORSAL ROOT GANGLION OF FEMALE RATS TO MECHANO-STIMULATION RELEVANT FOR LORDOSIS REFLEX

The activity of single units (n=312) was recorded from dorsal root ganglion L6 in female rats; 84% received input from cutaneous mechanoreceptors. Among cutaneous mechanoreceptive units (n=263), 22% responded to individual guard hair movement, 18% to down hair, 11% to clitoral hair, and 14% to stimulation of tylotrich hair-haarscheibe (type I) receptors, 5% responded to punctate skin deformation, but not hair movement or pressure, and 18% responded to pressure. No significant differences between estrogen-treated and untreated ovariectomized rats were observed in receptive-field size, or von Frey hair, or pressure threshold of any given type of unit. The lordosis reflex of female rats is triggered by pressure, but not hair deflection, on skin regions innervated by dorsal root L6 (10). Stimulation from the male rat mounting would cause a barrage of action potentials from most of the unit types identified here, but only pressure units and type I units gave sustained responses to a lordosis-triggering type of pressure stimulation.