6-Hydroxydopamine Nigrostriatal Lesion — P Calabresi | ReplicateScience

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6-Hydroxydopamine Nigrostriatal Lesion — P Calabresi | ReplicateScience

View Abstract

The effect of tetanic activation of corticostriatal glutamatergic fibers was studied in striatal slices by utilizing extracellular and intracellular recording techniques. Tetanic stimulation produced a long- term synaptic depression (LTD) (> 2 h) of both extracellularly recorded field potentials and intracellularly recorded EPSPs. LTD was not coupled with changes of intrinsic membrane properties of the recorded neurons. In some neurons, repetitive cortical activation produced a short-term posttetanic potentiation (1–3 min). Subthreshold tetanic stimulation, which under control condition did not cause LTD, induced LTD when associated with membrane depolarization. Moreover, LTD was not expressed in cells in which the conditioning tetanus was coupled with hyperpolarization of the membrane. Bath application of aminophosphonovalerate (30–50 microM), an antagonist of NMDA receptors, did not affect the amplitude of the synaptic potentials and the expression of LTD. Striatal LTD was significantly reduced by the pretreatment of the slices with 30 microM 2-amino-3-phosphonopropionic acid, an antagonist of glutamate metabotropic receptors. LTD was not blocked by bicuculline (30 microM), a GABA(A) receptor antagonist. Scopolamine (3 microM), an antagonist of muscarinic receptors, induced a slight, but significant, increase of the amplitude of LTD. Both SCH 23390 (3 microM), an antagonist of D1 dopamine (DA) receptors, and I- sulpiride (1 microM), an antagonist of D2 DA receptors, blocked LTD. LTD was also absent in slices obtained from rats in which the nigrostriatal DA system was lesioned by unilateral nigral injection of 6-hydroxydopamine. In DA-depleted slices, LTD could be restored by applying exogenous DA (30 microM) before the conditioning tetanus. In DA-depleted slices, LTD could also be restored by coadministration of SKF 38393 (3–10 microM), a D1 receptor agonist, and of LY 171555 (1–3 microM), a D2 receptor agonist. Application of a single class of DA receptor agonists failed to restore LTD. These data show that striatal LTD requires three main physiological and pharmacological conditions: (1) membrane depolarization and action potential discharge of the postsynaptic cell during the conditioning tetanus, (2) activation of glutamate metabotropic receptors, and (3) coactivation of D1 and D2 DA receptors. Striatal LTD may alter the output signals from the striatum to the other structures of the basal ganglia. This form of synaptic plasticity can influence the striatal control of motor activity.

Protocol Steps

1

Unilateral nigral injection of 6-hydroxydopamine

Perform unilateral injection of 6-hydroxydopamine into the substantia nigra to lesion the nigrostriatal dopamine system

Not specifiedNot specified

Note: This creates dopamine-depleted striatal slices for subsequent testing

View evidence from paper

“LTD was also absent in slices obtained from rats in which the nigrostriatal DA system was lesioned by unilateral nigral injection of 6-hydroxydopamine”

2

Prepare striatal slices

Prepare striatal slices from lesioned rats for electrophysiological recording

Not specifiedNot specified

Note: Slices should be from dopamine-depleted striatum following 6-hydroxydopamine lesion

View evidence from paper

“slices obtained from rats in which the nigrostriatal DA system was lesioned by unilateral nigral injection of 6-hydroxydopamine”

3

Set up extracellular and intracellular recordings

Position extracellular and intracellular recording electrodes in striatal slices to measure field potentials and EPSPs

Not specifiedNot specified

Note: Both recording techniques used simultaneously

View evidence from paper

“The effect of tetanic activation of corticostriatal glutamatergic fibers was studied in striatal slices by utilizing extracellular and intracellular recording techniques”

4

Apply exogenous dopamine to restore LTD

Apply exogenous dopamine at 30 microM concentration to dopamine-depleted slices before conditioning tetanus

Not specifiedNot specified

Note: This restores LTD expression in dopamine-depleted slices

View evidence from paper

“In DA-depleted slices, LTD could be restored by applying exogenous DA (30 microM) before the conditioning tetanus”

5

Apply D1 and D2 receptor agonists to restore LTD

Coadminister SKF 38393 (D1 agonist, 3-10 microM) and LY 171555 (D2 agonist, 1-3 microM) to dopamine-depleted slices

Not specifiedNot specified

Note: Both agonists must be applied together; single class of agonist alone fails to restore LTD

View evidence from paper

“In DA-depleted slices, LTD could also be restored by coadministration of SKF 38393 (3–10 microM), a D1 receptor agonist, and of LY 171555 (1–3 microM), a D2 receptor agonist. Application of a single class of DA receptor agonists failed to restore LTD”

6

Deliver tetanic stimulation

Apply tetanic stimulation to corticostriatal glutamatergic fibers to induce LTD

Not specifiedNot specified

Note: Tetanic stimulation produces LTD lasting greater than 2 hours

View evidence from paper

“Tetanic stimulation produced a long-term synaptic depression (LTD) (> 2 h) of both extracellularly recorded field potentials and intracellularly recorded EPSPs”

7

Record LTD expression

Monitor and record field potentials and EPSPs to measure LTD expression following tetanic stimulation

Greater than 2 hoursNot specified

Note: LTD is absent in dopamine-depleted slices but restored by dopamine or combined D1/D2 agonist application

View evidence from paper

“LTD was also absent in slices obtained from rats in which the nigrostriatal DA system was lesioned by unilateral nigral injection of 6-hydroxydopamine”