Anxiolytic-like effect of noradrenaline microinjection into the dorsal periaqueductal gray of rats

Abstract

The brain noradrenergic system has been implicated in the expression of defensive behaviors elicited by acute stress. The dorsal periaqueductal gray area (dPAG) is a key structure involved in the behavioral and cardiovascular responses elicited by fear and anxiety situations. Although there are noradrenergic terminals in the dPAG, few studies have investigated the role of noradrenaline (NA) in the dPAG on anxiety modulation. The aim of this study was to evaluate the effect of NA microinjection into the dPAG of rats subjected to two animal models of anxiety, the elevated plus-maze and the Vogel conflict test. Male Wistar rats implanted with a guide cannula aimed at the dPAG received microinjections of NA (3, 15, or 45 nmol/0.05 microl) or artificial cerebral spinal fluid into the dPAG immediately before being exposed to the elevated plus-maze or the Vogel conflict test. NA increased the exploration of the open arms and the number of enclosed arm entries in the elevated plus-maze. The increase in open arm exploration remained significant after being subjected to an analysis of covariance using the latter variable as covariate. Moreover, the NA microinjection into the dPAG did not increase general exploratory activity of animals subjected to the open-field test, indicating that the increase in open arm exploration cannot be attributed to a nonspecific increase in exploratory activity. In the Vogel test, the NA microinjection into the dPAG increased the number of punished licks without changing the number of nonpunished licks or interfering with the tail-flick test. The results, therefore, indicate that the NA microinjection into the dPAG produces anxiolytic-like effects, suggesting its possible involvement in the anxiety modulation.

The Antidepressant Effect of L-Tyrosine-Loaded Nanoparticles: Behavioral Aspects

“…According to Płaźnik et al [42] , intra-accumbens injection of NA or dopamine increased the rat rearing and locomotor activity in the open filed test. However, another study that used NA microinjection has shown no increase in the exploratory activity [43] . This contrast of results is probably attributed to the site of NA injection or the type of rearing activity recorded.…”

Gene Expression Changes in Glutamate and GABA-A Receptors, Neuropeptides, Ion Channels, and Cholesterol Synthesis in the Periaqueductal Gray Following Binge-Like Alcohol Drinking by Adolescent Alcohol-Preferring (P) Rats

“…Adra1a , an alpha adrenergic receptor subunit gene, also had decreased expression. Because norepinephrine injected into the PAG has an anxiolytic effect (Pelosi et al., ), the decrease in Adra1a could make these animals more prone to anxiety in stressful situations.…”

Identification of Neural Networks That Contribute to Motion Sickness through Principal Components Analysis of Fos Labeling Induced by Galvanic Vestibular Stimulation

“…The periaqueductal gray receives light projections from the vestibular nuclei [112], is connected reciprocally with the locus coeruleus [113], [114], and projects to the medial and lateral parabrachial nuclei [115]. Recent studies in rats indicate that Fos activation in locus coeruleus and the periaqueductal gray is observed in animals displaying escape responses in an elevated T-maze task [116], which may include recruitment of anxiolytic effects of norepinephrine via the dorsal periaqueductal gray [117].…”