Actophotometer

Actophotometer (Locomotor Activity Photocell Apparatus)

1. Definition, scope and terminology

• Actophotometer is the Indian-PG / CPCSEA colloquial name for an automated photocell-based locomotor-activity meter — a small chamber instrumented with an array of infra-red (IR) photocells whose light-beams the rodent interrupts during ambulation; each interruption is electronically counted as one "activity event". ⚠ The verbatim term actophotometer is the laboratory/curriculum shorthand and does NOT appear verbatim in the three primary source textbooks (Vogel 4e, SK Gupta, Medhi); the canonical textbook terms for the same class of apparatus are "photocell activity cage", "open-field photocell apparatus", "activity monitor", "photocell beam system", and "open field test" — used interchangeably in the literature. (Vogel V2 Part V, pp.1042–1049; SK Gupta Ch-26, p.395; SK Gupta Ch-30, p.460).
• Etymology: acto- (action / movement) + photo- (light) + -meter (measurement) → device that uses light-beam interruption to measure spontaneous motor activity.
• Object of measurement. Spontaneous motor activity of rodents — an umbrella term covering locomotion, rearing, sniffing, grooming, eating and drinking — was originally scored manually by skilled observers but is difficult to quantitate and reproduce; the actophotometer/photocell activity cage replaces the observer with a transducer (photocell → counter), giving an objective, continuous, observer-independent metric (Vogel V2 Part V, pp.1042–1043).
• Place in PG pharmacology. Falls under experimental pharmacology — animal models for CNS drug screening (RGUHS Paper III/IV). The apparatus is the single most widely deployed tool for first-line screening of:
  • CNS depressants (sedatives, hypnotics, anxiolytics) — produce hypoactivity
  • CNS stimulants (caffeine, amphetamines) — produce hyperactivity
  • Antipsychotics — block stimulant-induced hyperactivity; produce cataleptic hypoactivity at higher doses
  • Antidepressants — potentiate amphetamine-induced hyperactivity (TCA, MAOI); reverse isolation- or olfactory-bulbectomy-induced changes
  • Antiparkinsonian drugs — restore activity in MPTP/6-OHDA hypokinesia (SK Gupta Ch-26, p.395; SK Gupta Ch-27, p.407–409; SK Gupta Ch-30, p.460–462; Vogel V2 Part V, pp.1042–1049).