ISSN:
1432-1106
Keywords:
Past and slow principal cells
;
Recurrent inhibition
;
Lateral geniculate body
;
Rat
Source:
Springer Online Journal Archives 1860-2000
Topics:
Medicine
Notes:
Summary In urethane-anesthetized albino rats studies were made on mass potentials and/or unit activities of the lateral geniculate body (LGB) in response to single shock stimulation of optic tract (OT) and visual cortex (VC). The previous finding that LGB mass responses to stimulation of the optic nerve comprise at least two postsynaptic waves (r1 and r2) with different peak times was confirmed by OT stimulation. It was found that the r1 wave had a lower threshold and a more rapid recovery process than the r2 wave. Unit responses of principal (P) cells to maximal OT stimulation consisted of short-latency, single spikes (initial spike, IS), followed by long-latency, grouped discharges (late discharge, LD) repeated more than twice (LD1, LDr2 and so forth). Spontaneous discharges were almost completely suppressed after IS and each LD, suggesting that following these evoked discharges P cells underwent a phase of depressed excitability. The latency histogram of IS based upon 212 P cells had two peaks well-corresponding in time to the peaks of the r1 and r2 waves of the mass response, respectively. P cells were divided into the fast and slow groups according to whether their ISs occurred earlier or later than the trough separating the r1 and r2 waves. Typically, the fast cells had lower thresholds than the slow cells. The duration of the post-excitatory depression following IS and LD1 were shorter in the fast cells than in the slow cells. This same was found true with regard to the duration of depressed excitability following the antidromic firing. Examining the response patterns to OT stimulation of weak intensities, one characteristic difference between the two groups of P cells was found; the fast cells showed the IS without the succeeding LDs whereas the slow cells showed the LDs without the preceding IS. A discussion was made on functional significance of the differentiation of P cells into two types.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00234664
