Osmotic pump implant for chronic infusion of drugs into the inner ear

J. Nadine Brown, Josef M. Miller, Richard A. Altschuler, Alfred L. Nuttall

Research output: Contribution to journalArticlepeer-review

130 Scopus citations


Continuous long-term delivery of experimental drugs to the cochlea of a small animal, such as a young guinea pig, presents several technical problems. A method of placing and securing a cannula-osmotic pump system is described in this paper. Guinea pigs (225-410 g) were unilaterally implanted with an Alzet micro-pump and cannula for delivery of 20 mM tetrodotoxin (TTX) (six animals) or saline (three animals) for three days (1 μl/h). Auditory brainstem responses (ABRs) were recorded under light anesthesia on post-implant day 1 and day 3 and compared with pre-implant baseline values. In all six cochleas infused with TTX, most frequencies showed a 30-60dB decrease in sensitivity within 24 h. Saline control animals showed little or no change from baseline sensitivity for most frequencies. In three TTX-infused animals, the cannula-pump unit was removed on day 3, and ABRs were followed during recovery. Most frequencies returned to, or near, pre-implant levels after pump removal but recovery times varied. By day 6, all animals had recovered post-surgical weight loss and showed a gain of 10-40 g. Brains and cochleas were removed and processed for sectioning. Assessment of the cochlear nucleus of non-recovery TTX-treated animals showed a deafness-related flattening of auditory nerve active zones on the treated side.

Original languageEnglish (US)
Pages (from-to)167-172
Number of pages6
JournalHearing Research
Issue number2
StatePublished - Nov 1993
Externally publishedYes


  • Auditory nerve
  • Cochlea
  • Guinea pig
  • Synapse flattening
  • Tetrodotoxin

ASJC Scopus subject areas

  • Sensory Systems


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