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Influence of thermal stress on the expression of CB1 cannabinoid receptors in the rat mesencephalic trigeminal nucleus

A. Ivanov, A. Dandov, D. Atanasova, N. Dimitrov, N. Lazarov

Abstract

The mesencephalic trigeminal nucleus (Me5) is a unique brain structure that plays a crucial role in orofacial pro­prioception, and receives synaptic input from various brainstem regions regulating feeding behavior. It is com­posed mainly of large pseudounipolar neurons, which are glutamatergic, and a subset of smaller multipolar cells of GABAergic nature. Evidence shows that cannabinoid (CB) receptors and their endogenous ligands are wide­ly distributed in brainstem areas that are involved in pain sensation and feeding by influencing the glutamate and GABA neurotransmitter systems. This study aims at investigating the presence of a CB1 receptor, the major cannabinoid receptor subtype in the brain, in Me5 neurons after acute exposure to thermal stress, and pretreat­ment with its selective agonists and antagonists. We found that the administration of the endogenous CB1 agonist anandamide evokes an intense expression of CB1 receptors in the mesencephalic trigeminal neurons in rats ex­posed to short-term (up to 1 hour) thermal stress at 32-36°C, while injecting the synthetic CB1 antagonist AM251 decreases the levels of protein expression of this receptor in a hot-plate test. Our results provide immunohisto­chemical evidence that mild thermal stress triggers endocannabinoid release in a subset of Me5 neurons which utilize glutamate and GABA for synaptic transmission but lack CB1 receptor expression under normal condi­tions. These findings suggest a possible role for the Me5 endocannabinoid system in providing additional control to the complex neural network which modulates feeding in response to pain-triggering stimuli.





DOI: http://dx.doi.org/10.14748/ssm.v49i0.4848

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About The Authors

A. Ivanov
Medical University of Sofia
Bulgaria

A. Dandov
Medical University of Sofia
Bulgaria

D. Atanasova
Medical University of Sofia
Bulgaria

N. Dimitrov
Medical University of Sofia
Bulgaria

N. Lazarov
Medical University of Sofia
Bulgaria

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