Dose-response measures of rCBF and subjective changes following procaine in healthy female volunteers

[Langanhaltende Besserung von somatischen und psychovegetativen Störungen unter Procain-Infusionen: Eine multizentrische Anwendungsbeobachtung]

Hintergrund: Procain besitzt wie das strukturverwandte Cocain zentralnervöse Wirkungen unabhängig von seinem lokalanästhetischen Effekt. Procain-Infusionen werden Patienten mit psychovegetativen Störungen seit Jahrzehnten verabreicht, zumeist im Rahmen einer Neuraltherapie. Untersuchungen zur Wirksamkeit einer alleinigen Gabe von Procain im Praxisalltag stehen aus. Patienten und Methoden: Im Rahmen einer Anwendungsbeobachtung (AWB) wurde bei 56 Patienten aus 3 Arztpraxen die Wirkung von intravenösen Procain-Infusionen (1-3 Ampullen à 5 ml einer 2%igen Procain-Lösung in 250 ml Natriumchlorid pro Arztbesuch) auf das somatische und psychovegetative Befinden dokumentiert. Hierzu wurde ein validierter, 21 Fragen umfassender Befindlichkeitsskalierungsfragebogen verwendet, den die Patienten vor Beginn und nach 1, 2, 4 und 6 Monaten ausfüllten. Neben der laufenden Medikation waren keine weiteren therapeutischen Maßnahmen erlaubt. Ergebnisse: Nach 4 oder 6 Monaten zeigten 42 Patienten (75%) eine Verbesserung bei den 9 positiven Items (d.h. erfragte Eigenschaften) wie «Freude», «Genussfähigkeit» oder «Schlaf»; 35 Patienten (62,5%) verbesserten sich bei den 12 negativen Items wie «Stressbelastung», «Energielosigkeit» oder «Ängstlichkeit». Diese Veränderungen waren nach 2, 4 und 6 Monaten signifikant gegenüber dem Ausgangswert. Schlussfolgerungen: Procain ruft im zentralen Nervensystem nachweislich Veränderungen in der Aktivität spezifischer Kerngebiete wie des limbischen und kortikalen Systems hervor. Die Ergebnisse dieser AWB deuten auf eine langanhaltende Verbesserung von somatischen und psychovegetativen Störungen unter der Infusion von Procain.

Neural response to lidocaine in healthy subjects

Recent studies suggest that some of cocaine's central nervous system (CNS) effects may be mediated through its sodium channel inhibiting local anesthetic properties. Local anesthetics that lack cocaine's strong affinity for the dopamine transporter (DAT) also produce sensory and mood effects, further suggesting a role for this neural pathway. Due to an absence of affinity at the DAT, the local anesthetic lidocaine may offer the potential to assess sodium channel activity in vivo in humans. To assess the utility of lidocaine as a CNS probe, we determined regional cerebral blood flow (rCBF) with single photon emission computed tomography (SPECT) following the intravenous administration of lidocaine (0.5 mg/kg) and compared this response to procaine (0.5 mg/kg and 1.0 mg/kg), a local anesthetic with partial affinity for the DAT, and saline. Infusions were administered in nine healthy female controls over a 10-day period with at least 2 days between each scan. Increased rCBF was observed following lidocaine, relative to saline, in the insula, caudate, thalamus, and posterior cingulate. Decreased rCBF was detected in a different region of the posterior cingulate. In general, increases in rCBF were more marked following lidocaine relative to procaine. Mood and sensory changes following lidocaine were limited and significantly less than those induced by either dose of procaine. There were no significant changes in blood pressure or heart rate following either medication. These findings suggest that lidocaine can be safely used to assess sodium channel function in persons with addictive and other psychiatric disorders.

Gender differences in limbic responsiveness, by SPECT, following a pharmacologic challenge in healthy subjects

Limbic system functioning is integral to the control and modulation of affect, motivation, reward, and memory. Neuropsychiatric disturbances involving disruptions in these cognitive and emotional dimensions exhibit different prevalence rates for men and women. Gender-specific differences in this integrated brain area may therefore be important in understanding both normal behavioral functioning and the etiologic underpinnings of neuropsychiatric disorders. To further explore such differences in limbic system function, we assessed regional cerebral blood flow, by SPECT, in men and women following the administration of procaine. Procaine is a local anesthetic that preferentially stimulates limbic structures. Psychiatrically and medically healthy, age-matched women (n = 15, 33.2 +/- 6.9 years) and men (n = 15, 32.8 +/- 6.9 years) were administered 1.38 mg/kg procaine or saline intravenously in two separate sessions. Using voxel-based analyses (P < 0.001), males significantly activated the bilateral insular cortex following procaine, whereas females more strongly activated the bilateral anterior and mesial temporal cortex. Both groups demonstrated significant anterior cingulate activation. Subjective responses to procaine did not significantly differ between the men and women. To our knowledge, this is the first report demonstrating gender-specific responses in limbic activation following a pharmacologic challenge. These findings suggest that men and women can activate different limbic structures following the same provocative pharmacologic stimulus, despite sharing a similar subjective experience. Studies assessing pharmacologic challenges of limbic system structures should consider gender as a critical variable in assessing biologic responsiveness.