Changes in hair growth (3)

Changes in hair growth (3)

Wounding experiments
30 male rats of six months of age were utilized for all experiments. Anaesthesia
was induced by intraperitoneal injection of Sagatal, 0-055 ml/100 g body weight.
The method employed to expose follicles for operation was the same as that
used by Cohen (1961) and Oliver (1966a). After being cleaned of surrounding

Hair growth changes following vibrissa wounding

Diagram of the four different methods used to injure the whisker follicles.

connective tissue, the positional identity of prospective experimental follicles
was confirmed and recorded. For convenience, operations were performed on
the left-hand side of the face. Damage was inflicted on follicles which were
growing hairs (in anagen) using finely pointed tungsten needles mounted on glass
rods. A diagrammatic representation of the four operational techniques is shown
in Figure Method I (la): A needle was inserted horizontally into the bulb region of a
follicle, and then rotated to disrupt the dermal papilla. 52 follicles operated on
in this manner were kept under long term observation.
Method II (lb): With this procedure, the follicle capsule was initially
penetrated distal to the bulb region, about one third of the way up the follicle.
The needle was then carefully pushed into the middle of the papilla, and rotated
as before. 18 follicles were kept under regular scrutiny.

Method III (lc): Follicles were damaged as for method II. However, in these
specimens injury to the dermal papilla was preceded by plucking of the club and
growing fibres prior to the introduction of the needle. 12 follicles damaged in this
manner were used for extended observations. In addition vibrissae were plucked
from 20 follicles in four animals to examine the effects of a single epilation on
whisker length. 10 of these had emergent fibres extracted after removal of the
club hair, while with the remaining 10 follicles only the growing hairs were plucked.
Method IV (Id): As a control, a further 19 follicles underwent penetration of
the capsule and follicle wall at a level above the bulb and thus without subsequent
injury to the proximal region or dermal papilla.