Rapid differential conditioning of the somatosensory evoked potential by changed patterns of brief innocuous tactile stimuli in waking rats is altered by atropine sulfate
Rw. Dykes et al., Rapid differential conditioning of the somatosensory evoked potential by changed patterns of brief innocuous tactile stimuli in waking rats is altered by atropine sulfate, BRAIN RES, 910(1-2), 2001, pp. 74-80
Air puffs delivered to the nose of an awake, lightly restrained rat every 1
5 s produced evoked potentials that changed gradually over time so that the
averaged response to the last 40 stimuli was measurably different from the
first 40. This habituation-like paradigm increased the size of an early co
mponent of the potential in several places. When measured with respect to t
he time of stimulus onset (there was a 21.6 ms delay in the time of arrival
of the stimulus maximum at the nose), one of the largest increases occurre
d 46 ms later (39 ms latency to onset, and 55 ms latency to offset). As wel
l, a late component of the waveform became more positive, showing a maximum
between 156 and 185 ms (133 ms latency to onset, and more than 250 ms late
ncy to offset). Changing the pattern but not the number of stimuli accelera
ted the rate of this positive shift with a maximum at 37 ms (21 ms latency
to onset, and 42 ms latency to offset), but did not affect the rate of chan
ge in the late component. This effect of altering the temporal pattern of t
he stimuli was blocked by systemic injections of atropine sulfate, a blocke
r of central muscarinic receptors, whereas, neither saline injections nor a
tropine methyl nitrate injections (an atropine analog that does not cross t
he blood-brain barrier) could produce these changes. These observations sug
gest that the adaptive changes of the somatosensory evoked potential induce
d by novel patterns intercalated in otherwise monotonous repetitive somatic
stimuli depend upon central muscarinic mechanisms. (C) 2001 Elsevier Scien
ce B.V. All rights reserved.