Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1992 Dec 11;598(1-2):173-84.
doi: 10.1016/0006-8993(92)90181-8.

Factors regulating the magnitude of long-term potentiation induced by theta pattern stimulation

A Arai  1 , G Lynch
Affiliations

Factors regulating the magnitude of long-term potentiation induced by theta pattern stimulation

A Arai et al. Brain Res. .

Abstract

Electrical stimulation patterned after the hippocampal theta rhythm produces a robust and stable long-term potentiation (LTP) effect. Pharmacological manipulations were used in the present studies in an effort to relate characteristics of the responses occurring during theta stimulation to the magnitude of potentiation which follows it. Comparisons were made using five or ten bursts of stimulation which respectively induce sub-maximal or near maximal degrees of LTP. DPCPX, a drug that increases release by blocking adenosine A1 receptors, was used to enhance the depolarization produced by individual theta bursts. This resulted in a marked increase in the amount of stable LTP induced by five theta bursts but did not affect that resulting from ten bursts. This finding suggested that depolarization occurring during a burst response influences per burst potentiation but not the ceiling on maximum LTP. Aniracetam, a nootropic drug that enhances responses via an action on glutamate (AMPA) receptors, was used to test this conclusion. Like DPCPX, aniracetam increased the size of the burst response and enhanced the degree of LTP caused by five but not ten theta bursts. Forskolin, an activator of adenylate cyclase, was used to test the effects of blocking the hyperpolarization normally present between theta bursts on the induction of LTP. The drug augmented the degree of LTP resulting from five theta bursts and, in contrast to DPCPX and aniracetam, nearly doubled that obtained with ten bursts. Thus the drug affected both per burst potentiation and the ceiling on LTP. These results are discussed in terms of an hypothesis in which the magnitude of NMDA receptor mediated currents affects the degree of potentiation produced by individual theta bursts while the duration of the currents is related to the limit on the maximum LTP induced by a series of bursts. The possible implications of the findings for learning are also considered.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

Publication types

LinkOut - more resources