1 Cholinergic neurons were Identified in rat striatal slices by their size,
membrane properties, sensitivity to the NK1 receptor agonist (Sar(9). Met(
O-2)(11)) Substance P, and expression of choline acetyltransferase mRNA. A(
1) receptor mRNA was detected in 60% of the neurons analysed, and A(2A) rec
eptor mRNA in 67% (n = 15).
2 The A(1) receptor agonist R-N-o-(2-phenylisopropyl)adenosine (R-PIA) hype
rpolarized cholinergic neurons rn a concentration dependent manner sensitiv
e to the At antagonist 8-cyclopentyl-1,3-dipropylxanthine (DPCPX, 100 nM).
3 In dual stimulus experimental the A(2A) receptor antagonist 8-(3-chlorost
ytyl)caffeine (CSC, 500 nM) decreased release of [H-3]-acetylcholine from s
triatal slices (S2/S1 0.78+/-0.07 versus 0.95+/-0.05 in control), as did ad
enosine deaminase (S2/S1 ratio 0.69+/-0.05), whereas the A(1) receptor anta
gonist DPCPX (100 nM) had no effect (S2/S1 1.05+/-0.14).
4 In the presence of adenosine deaminase the adenosine A(2A) receptor agoni
st 2-p-((carboxyethyl)phenylethylamino) -5'-N-ethylcarboxamidoadenosine (CG
S21680, 10 nM) increased release (S2/S1 ratio 1.03 +/- 0.05 Versus 0.88 +/-
0.05 in control), an effect blocked by the antagonist CSC (500 nM, S2/S1 0
.68 +/- 0.05. versus 0.73 +/- 0.08 with CSC alone). The combined superfusio
n of bicuculline (10 mu M), saclofen (1 mu M) and naloxone (10 mu M) had no
effect on the stimulation by CGS21680 (S2/S1 ratio 0.99 +/- 0.04).
5 The A(1) receptor agonist R-PIA (100 nM) inhibited the release of [H-3]-a
cetylcholine (S2/S1 ratio 0.70 +/- 0.03). an effect blocked by DPCPX (S2/S1
ratio 1.06 +/- 0.07).
6 It is concluded that both A(1) and A(2A) receptors are expressed on stria
tal cholinergic neurons where they are functionally active.