Prolonged cannabinoid treatment results in spatial working memory deficits and impaired long-term potentiation in the CA1 region of the hippocampus in vivo

Hippocampal long-term potentiation (LTP) is a form of synaptic plasticity used as a cellular model of memory. Beta amyloid (Aβ) is involved in Alzheimer's disease (AD), a neurode-generative disorder leading to cognitive deficits. Nicotine is also claimed to act as a cognitive enhancer. Aβ is known to bind with high affinity to the α7-nicotinic acetylcholine receptor (nAChR). Here we have investigated the effect of intracerebroventricular (icv) injection of the endogenous peptide Aβ1–40 on LTP in area CA1 of urethananesthetized rats. We also examined the effect of Aβ12–28 (icv), which binds with high affinity to the α7-nAChR and the specific α7-nAChR antagonist methyllycaconitine (MLA) on LTP. We found that Aβ12–28 had no effect on LTP, whereas MLA depressed significantly LTP, suggesting that activation of the α7-nAChR is a requirement for LTP. Within the in vivo environment, where other factors may compete with Aβ12–28 for binding to α7-nAChR, it does not appear to modulate LTP. To determine if the depressive action of Aβ1–40 on LTP could be modulated by nicotine, these agents were also co-applied. Injection of 1 or 10 nmol Aβ1–40 caused a significant depression of LTP, whereas nicotine alone (3 mg/kg) had no effect on LTP. Co-injection of nicotine with Aβ1–40 1 h prior to LTP induction caused a further significant depression of LTP compared with Aβ1–40 alone. These results demonstrate that nicotine enhances the deficit in LTP produced by Aβ1–40. This then suggests that nicotine may exacerbate the depressive actions of Aβ on synaptic plasticity in AD.

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Effects of perfluorooctane sulfonate and its alternatives on long-term potentiation in the hippocampus CA1 region of adult rats in vivo

Toxicology Research ◽

10.1039/c5tx00184f ◽

2016 ◽

Vol 5 (2) ◽

pp. 539-546 ◽

Cited By ~ 18

Author(s):

Qian Zhang ◽

Wei Liu ◽

Qiao Niu ◽

Yu Wang ◽

Huimin Zhao ◽

...

Keyword(s):

Health Effects ◽

Perfluorooctane Sulfonate ◽

Long Term Potentiation ◽

Adult Rats ◽

Ca1 Region ◽

Term Potentiation

With the limited but ongoing usage of perfluorooctane sulfonate (PFOS), the health effects of both PFOS and its alternatives are far from being understood.

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Role of constitutive calcium-independent phospholipase A2 beta in hippocampo-prefrontal cortical long term potentiation and spatial working memory

Neurochemistry International ◽

10.1016/j.neuint.2014.08.006 ◽

2014 ◽

Vol 78 ◽

pp. 96-104 ◽

Cited By ~ 6

Author(s):

Suku-Maran Shalini ◽

Wee-Siong Chew ◽

Ramamoorthy Rajkumar ◽

Gavin S. Dawe ◽

Wei-Yi Ong

Keyword(s):

Working Memory ◽

Phospholipase A2 ◽

Spatial Working Memory ◽

Long Term Potentiation ◽

Prefrontal Cortical ◽

Term Potentiation ◽

Calcium Independent Phospholipase A2

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Aβ25–35-Induced Depression of Long-Term Potentiation in Area CA1 In Vivo and In Vitro Is Attenuated by Verapamil

Journal of Neurophysiology ◽

10.1152/jn.00992.2002 ◽

2003 ◽

Vol 89 (6) ◽

pp. 3061-3069 ◽

Cited By ~ 46

Author(s):

D. B. Freir ◽

D. A. Costello ◽

C. E. Herron

Keyword(s):

Long Term Potentiation ◽

Slice Preparation ◽

Ca1 Region ◽

Combined Application ◽

Significant Reversal ◽

Term Potentiation ◽

Prior Application

The effect of intracerebroventricular (icv) injection of Aβ25–35 and/or intraperitoneal (ip) application of the L-type calcium channel (VDCC) blockers verapamil or diltiazem were examined in vivo. To by-pass possible systemic actions of these agents, their effects on long-term potentiation (LTP) in the CA1 region of the in vitro hippocampal slice preparation were also examined. Application of Aβ25–35 (10 nmol in 5 μl, icv) significantly impaired LTP in vivo, as did IP injection of verapamil (1 or 10 mg/kg) or diltiazem (1 or 10 mg/kg). In the in vitro slice preparation, LTP was also depressed by prior application of Aβ25–35 (500 nmol), verapamil (20 μM), or diltiazem (50 μM). Combined application of Aβ25–35 and verapamil in either the in vivo or in vitro preparation resulted in a significant reversal of the LTP depression observed in the presence of either agent alone. However, co-application of diltiazem and Aβ25–35 failed to attenuate the depression of LTP observed in the presence of either agent alone in vivo or in vitro. Since LTP is a cellular correlate of memory and Aβ is known to be involved in Alzheimer's disease (AD), these results indicate that verapamil, a phenylalkylamine, may be useful in the treatment of cognitive deficits associated with AD.

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Blockade of Long-Term Potentiation by β-Amyloid Peptides in the CA1 Region of the Rat Hippocampus In Vivo

Journal of Neurophysiology ◽

10.1152/jn.2001.85.2.708 ◽

2001 ◽

Vol 85 (2) ◽

pp. 708-713 ◽

Cited By ~ 112

Author(s):

Darragh B. Freir ◽

Christian Holscher ◽

Caroline E. Herron

Keyword(s):

Long Term Potentiation ◽

Amyloid Peptide ◽

Excitatory Postsynaptic Potential ◽

Dependent Manner ◽

Aβ Peptides ◽

Ca1 Region ◽

Term Potentiation ◽

Β Amyloid

The effect of intracerebroventricular (icv) injections of β-amyloid peptide fragments Aβ[15–25], Aβ[25–35], and Aβ[35–25] were examined on synaptic transmission and long-term potentiation (LTP) in the hippocampal CA1 region in vivo. Rats were anesthetized using urethan, and changes in synaptic efficacy were determined from the slope of the excitatory postsynaptic potential (EPSP). Baseline synaptic responses were monitored for 30 min prior to icv injection of Aβ peptides or vehicle. High-frequency stimulation (HFS) to induce LTP was applied to the Schaffer-collateral pathway 5 min or 1 h following the icv injection. HFS comprised 3 episodes of 10 stimuli at 200 Hz, 10 times, applied at 30-s intervals. Normal LTP measured 30 min following HFS, was produced following icv injection of vehicle (191 ± 17%, mean ± SE, n = 6) or Aβ[15–25; 100 nmol] (177 ± 6%, n = 6) 1 h prior to HFS. LTP was, however, markedly reduced by Aβ[25–35; 10 nmol] (129 ± 9%, n = 6, P < 0.001) and blocked by Aβ[25–35; 100 nmol] (99 ± 6%, n = 6, P < 0.001). Injection of the reverse peptide, Aβ[35–25], also impaired LTP at concentrations of 10 nmol (136 ± 3%, n = 6, P < 0.01) and 100 nmol (144 ± 7, n = 8, P < 0.05). Using a different protocol, HFS was delivered 5 min following Aβ injections, and LTP was measured 1 h post HFS. Stable LTP was produced in the control group (188 ± 15%, n = 7) and blocked by Aβ[25–35, 100 nmol] (108 ± 15%, n = 6, P < 0.001). A lower dose of Aβ[25–35; 10 nmol] did not significantly impair LTP (176 ± 30%, n = 4). The Aβ-peptides tested were also shown to have no significant effect on paired pulse facilitation (interstimulus interval of 50 ms), suggesting that neither presynaptic transmitter release or activity of interneurons in vivo are affected. The effects of Aβ on LTP are therefore likely to be mediated via a postsynaptic mechanism. This in vivo model of LTP is extremely sensitive to Aβ-peptides that can impair LTP in a time- ([25–35]) and concentration-dependent manner ([25–35] and [35–25]). These effects of Aβ-peptides may then contribute to the cognitive deficits associated with Alzheimer's disease.

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