PT  - JOURNAL ARTICLE
AU  - L Winsky
AU  - JA Harvey
TI  - Retardation of associative learning in the rabbit by an adenosine analog as measured by classical conditioning of the nictitating membrane response
AID  - 10.1523/JNEUROSCI.06-09-02684.1986
DP  - 1986 Sep 01
TA  - The Journal of Neuroscience
PG  - 2684--2690
VI  - 6
IP  - 9
4099  - http://www.jneurosci.org/content/6/9/2684.short
4100  - http://www.jneurosci.org/content/6/9/2684.full
SO  - J. Neurosci.1986 Sep 01; 6
AB  - A series of 5 experiments examined the effects of the adenosine agonist, N6-(L-phenylisopropyl) adenosine (L-PIA) and its isomer, D- PIA, on the acquisition of conditioned responses in the rabbit. Extension of the nictitating membrane was classically conditioned to a tone and light stimulus presented for 800 msec before delivery of a 100 msec shock--the unconditioned stimulus--to the skin over the paraorbital region of the head. L-PIA (5.0 mumol/kg) retarded the rate of acquisition of conditioned responses to both the tone- and light- conditioned stimuli, while D-PIA, at doses of 5.0 and 10.0 mumol/kg, had no significant effect. Control experiments employing the explicitly unpaired presentations of tone, light, and shock stimuli indicated that the retarded acquisition of conditioned responses produced by L-PIA was due to an action on associative learning. L-PIA had no effect on the threshold of the shock's eliciting of the unconditioned response nor on the amplitude of the elicited response, but produced a large and significant reduction in the ability of the tone-conditioned stimulus to evoke conditioned responses. It was concluded that L-PIA blocked the rate of associative learning by decreasing the excitatory properties of conditioned stimuli. These effects of L-PIA suggest that endogenous adenosine may act to modulate the rate of associative learning.