Peculiar response to methylphenidate in adolescent compared to adult rats: a phMRI study.
BACKGROUND
Adolescent rodents differ markedly from adults in several neuro-behavioural parameters. Moreover, 'paradoxical' responses to psychostimulants have been reported at this age.


OBJECTIVE
Thus, we investigated the responses of adolescent (post-natal day, PND, 34 to 43) and adult (PND >60) Sprague-Dawley male rats to the psychostimulant drug methylphenidate (MPH). We used pharmacological magnetic resonance imaging (phMRI) performed at 4.7 T under isoflurane anaesthesia. Following anatomical MRI, axial gradient echo images were collected continuously. After baseline recording (32 min), animals received MPH (0 or 4 mg/kg i.p.) and were recorded for further 32 min.


RESULTS
Region-specific changes in the blood-oxygenation level dependent (BOLD) signal were evident as a function of age. As expected, among adults MPH induced an increase of BOLD signal in nucleus accumbens (NAcc) and prefrontal cortex (PFC), with no effects in the hippocampus (Hip). Notably, among adolescents, MPH induced a marked and generalised decrease of BOLD signal, which occurred earlier in NAcc and PFC whilst being delayed in the Hip. Any bias in BOLD responses was excluded by the measurement of physiological parameters.


CONCLUSIONS
The present findings highlight the utility of phMRI in animal models. The peculiar negative BOLD effect found in adolescent rats may be suggestive of a reduced cerebro-vascular feedback and/or an increased MPH-induced neuronal activation. Data are relevant for a better understanding of brain/behavioural regulation during adolescent development. Moreover, a greater understanding of the differences between adult and adolescent drug responses will aid in the development of a more appropriate age-specific treatment strategy.
Canese
Rossella
R
Molecular and Cellular Imaging Section, Department of Cell Biology & Neurosciences, Istituto Superiore di Sanitá, viale Regina Elena, 299, 00161, Rome, Italy.
Adriani
Walter
W
Marco
Eva M
EM
De Pasquale
Francesco
F
Lorenzini
Paola
P
De Luca
Nicoletta
N
Fabi
Fulvia
F
Podo
Franca
F
Laviola
Giovanni
G
D000367:Age Factors; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001921:Brain / Q000098:blood supply* / Q000187:drug effects* / Q000254:growth & development; D001931:Brain Mapping / Q000379:methods*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006624:Hippocampus / Q000098:blood supply / Q000187:drug effects; D008279:Magnetic Resonance Imaging; D008297:Male; D008774:Methylphenidate / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects; D009714:Nucleus Accumbens / Q000098:blood supply / Q000187:drug effects; D017397:Prefrontal Cortex / Q000098:blood supply / Q000187:drug effects; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors
D000697:Central Nervous System Stimulants; D008774:Methylphenidate