Vater, Marianne and Habbicht, Hartmann and Kössl, Manfred and Grothe, Benedikt
The functional role of GABA and glycine in monaural and binaural processing in the inferior colliculus of horseshoe bats.
In: Journal of Comparative Physiology A, Vol. 171: pp. 541-553
The functional role of GABA and glycine in
monaural and binaural signal analysis was studied in
single unit recordings from the central nucleus of the
inferior colliculus (IC) of horseshoe bats (Rhinolophus
rouxi) employing microiontophoresis of the putative
neurotransmitters and their antagonists bicuculline and
Most neurons were inhibited by GABA (98%;
N= 107) and glycine (92%; N = 118). Both neurotransmitters
appear involved in several functional contexts,
but to different degrees.
Bicuculline-induced increases of discharge activity
(99% of cells; N= 191) were accompanied by changes of
temporal response patterns in 35 % of neurons distributed
throughout the IC. Strychnine enhanced activity in only
53% of neurons (N= 147); cells exhibiting response pattern
changes were rare (9%) and confined to greater
recording depths. In individual cells, the effects of both
antagonists could markedly differ, suggesting a differential
supply by GABAergic and glycinergic networks.
Bicuculline changed the shape of the excitatory tuning
curve by antagonizing lateral inhibition at neighboring
frequencies and/or inhibition at high stimulation levels.
Such effects were rarely observed with strychnine.
Binaural response properties of single units were influenced
either by antagonization of inhibition mediated
by ipsilateral stimulation (bicuculline) or by changing the
strength of the main excitatory input (bicuculline and