The Journal of Neurophysiology Vol. 85 No. 5 May 2001, pp. 2203-2212
Copyright ©2001 by the American Physiological Society
Postnatal Development of Inhibitory Synaptic Transmission in the
Rostral Nucleus of the Solitary Tract
Gintautas
Grabauskas1 and
Robert M.
Bradley1,2
1Department of Biologic and Materials
Sciences, School of Dentistry and 2Department of
Physiology, Medical School, University of Michigan, Ann Arbor, Michigan
48109
Grabauskas, Gintautas and
Robert M. Bradley.
Postnatal Development of Inhibitory Synaptic Transmission in the
Rostral Nucleus of the Solitary Tract. J. Neurophysiol. 85: 2203-2212, 2001. To explore the postnatal
development of inhibitory synaptic activity in the rostral (gustatory)
nucleus of the solitary tract (rNST), whole cell and gramicidin
perforated patch-clamp recordings were made in five age groups of rats
[postnatal day 0-7 (P0-7), P8-14,
P15-21, P22-30, and P >55]. The
passive membrane properties of the developing rNST neurons as well as
the electrophysiological and pharmacological characteristics of single
and tetanic stimulus-evoked inhibitory postsynaptic potentials (IPSPs)
were studied in brain slices under glutamate receptor blockade. During
the first postnatal weeks, significant changes in resting membrane
potential, spontaneous activity, input resistance, and neuron membrane
time constant of the rNST neurons occurred. Although all the IPSPs
recorded were hyperpolarizing, the rise and decay time constants of the single stimulus shock-evoked IPSPs decreased, and the inhibition response-concentration function to the 
-aminobutyric acid (GABA) receptor antagonist bicuculline methiodide (BMI) shifted to the left
during development. In P0-7 and P8-14, but not
in older animals, the IPSPs had a BMI-insensitive component that was
sensitive to block by picrotoxin, suggesting a transient expression of
GABAC receptors. Tetanic stimulation resulted in
both short- and long-term changes of inhibitory synaptic transmission
in the rNST. For P0-7 and P8-14 animals tetanic
stimulation resulted in a sustained hyperpolarization that was
maintained for some time after termination of the tetanic stimulation.
In contrast, tetanic stimulation of neurons in P15-21 and
older animals resulted in hyperpolarization that was not sustained but
decayed back to a more positive level with an exponential time course.
Tetanic stimulation resulted in potentiation of single stimulus
shock-evoked IPSPs in ~50% of neurons in all age groups. These
developmental changes in inhibitory synaptic transmission in the rNST
may play an important role in shaping synaptic activity in early
development of the rat gustatory system during a time of maturation of
taste preferences and aversions.
