Methylphenidate modulates dorsal raphe neuronal activity: Behavioral and neuronal recordings from adolescent rats

Abstract

Methylphenidate (MPD) is a widely prescribed psychostimulants used for the treatment of attention deficit hyperactive disorder (ADHD). Unlike the psychostimulants cocaine and amphetamine, MPD does not exhibit direct actions on the serotonin transporter, however there is evidence suggesting that the therapeutic effects of MPD may be mediated in part by alterations in serotonin transmission. This study aimed to investigate the role of the dorsal raphe (DR) nucleus, one of the major sources of serotonergic innervation in the mammalian brain, in the response to MPD exposure. Freely behaving adolescent rats previously implanted bilaterally with permanent electrodes were used. An open field assay and a wireless neuronal recording system were used to concomitantly record behavioral and DR electrophysiological activity following acute and chronic MPD exposure. Four groups were used: one control (saline) and three experimental groups treated with 0.6, 2.5, and 10.0 mg/kg MPD respectively. Animals received daily MPD or saline injections on experimental days 1–6, followed by 3 washout days and MPD rechallenge dose on experimental day (ED)10. The same chronic dose of MPD resulted in either behavioral sensitization or tolerance, and we found that neuronal activity recorded from the DR neuronal units of rats expressing behavioral sensitization to chronic MPD exposure responded significantly differently to MPD rechallenge on ED10 compared to the DR unit activity recorded from animals that expressed behavioral tolerance. This correlation between behavioral response and DR neuronal activity following chronic MPD exposure provides evidence that the DR is involved in the acute effects as well as the chronic effects of MPD in adolescent rats.

Immunotherapy as a treatment to confront the ongoing opioid epidemic- A review

“…Previous studies on the neurophysiologic properties underlying drug dependence have established that repetitive administration of morphine and other drugs of abuse modulate the behavioral and neuronal baseline (spontaneous) activities. These changes in spontaneous neuronal baseline activities in a large number of brain regions has been observed by us in 15 brain areas as follows: in the substantia nigra [ 37 ]; ventral tegmental area [ 38 ], locus coeruleus [ 38 ], dorsal raphe [ 39 ], nucleus accumbens [ 40 ], caudate nucleus [ 41 ], several thalamic [ 42 ] and several hypothalamic nuclei [ 42 ], reticular formation and central gray [ 37 ], hippocampus [ 42 ], amygdala [ 37 ], habenula [ 43 ], septum [ 37 ], and pre-frontal cortex [ 41 ]. These neurophysiologic changes correlate closely with the expression of tolerance and withdrawal and suggest a cause-effect relationship.…”

Prevention of Opioid Addiction

“…Corticosteroids are nonspecifi c immunosuppressors because they aff ect macrophages and monocytes as well as T-cells and B-cells, and hence cell-mediated and humoralmediated immune processes [90]. Aside from inducing a lymphopenia by redistributing circulating lymphocytes to other lymphoid compartments [91][92][93][94][95][96][97], glucocorticoids suppress type 2 cytokines such as IL-2 and IL-4 which are responsible for memory T cell diff erentiation as well as helper T cell diff erentiation and B-cell isotype switching to IgE [98].…”