EXCESS DIETARY VITAMIN-B6 ALTERS STARTLE BEHAVIOR OF RATS

Excessive intakes of vitamin B-6 can produce peripheral nervous system abnormalities, but few reports of central nervous system effects exis t. We measured startle response, a central nervous system reflex, in r ats fed excess pyridoxine to determine if subtle effects on central ne rvous system function could be detected. Female Long-Evans rats (218 g ; n = 12) were fed either 1, 10, 100, 200 or 300 times the requirement of pyridoxine HCI (7 mg/kg) for 7 wk. Startle behavior was assessed w eekly in chambers that allowed quantification of movement in response to stimuli. Food intake and body weights did not differ among groups ( P > 0. 1), and urinary vitamin B-6 excretion reflected intake (P < 0.0 01). Overt toxicity was not observed. There was a marginally significa nt effect of pyridoxine intake over time (P = 0.053) on the amplitude of response to a startling acoustic stimulus (117 dB, 40 ms) administe red alone; the response appeared attenuated at the three highest pyrid oxine concentrations. When the same stimulus was preceded by either a 70- or 75-dB prepulse (40 ms), responses of groups fed the two highest pyridoxine concentrations were significantly reduced relative to thos e fed the two lowest concentrations (P < 0.05). No effect of diet was seen with a startling tactile stimulus. Changes in central nervous sys tem function were detected in rats fed excess vitamin B-6 using techni ques of startle behavior measurement.